ALBERT

Description: 〈p〉Publication date: Available online 31 October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering〈/p〉 〈p〉Author(s): Vladimir A. Osinov, Stylianos Chrisopoulos, Theodoros Triantafyllidis〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The paper presents a numerical analysis of the dynamic deformation of the tunnel lining and the soil caused by a blast-induced pressure pulse of a moderate amplitude (several megapascals) inside the tunnel. The tunnel lining is circular and consists of individual concrete linearly elastic tubbings. The tunnel is located at a depth of 15 m in fully saturated granular soil. Effective-stress changes are described by a hypoplasticity model. The possibility of pore water cavitation at zero absolute pore pressure is taken into account. The problem is solved in a two-dimensional plane-strain formulation with the finite-element program Abaqus/Standard. Emphasis is placed on fine spatial discretization in order to obtain accurate solutions. Stresses and deformations in the lining and in the soil are analysed in detail. The solutions reveal an important role of the strong nonlinearity in the soil behaviour due to the pore water cavitation.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 31 October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering〈/p〉 〈p〉Author(s): J. Machaček, Th. Triantafyllidis, P. Staubach〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Earthquake stability assessment of large opencast mine slopes are complex and non-linear problems, often addressed using pseudo-static approaches neglecting material-induced failures and the role of pore-fluids. In this study, a numerical approach is used to understand the dynamic response of saturated and partially saturated soils. For this purpose user-defined elements have been implemented in 〈em〉Abaqus/Standard〈/em〉 including user-defined material models. The governing equations involving coupled fluid flow and finite deformation processes in partially saturated soils are derived within the framework of the 〈em〉Theory of Porous Media〈/em〉. The stress-strain behavior of granular soils is represented by a 〈em〉hypoplastic〈/em〉 constitutive model and for clayey soils the 〈em〉ISA-Clay〈/em〉 model is used. The saturation-suction behavior is modeled using the 〈em〉van Genuchten〈/em〉 model. To account for the large scale of the finite element model, a scaling procedure of the system of equations is proposed to purge the influence of initial stress. The performance of the user-defined elements is tested by back analysis of a centrifuge test available in the literature. Finally, large-scale fully coupled finite element simulations are performed to study the response of a flooded opencast mine under earthquake loading. The paper illustrates the importance of accounting the pore-fluids as independent phases in the context of seismic analysis of slopes and the influence of simplifications on which the calculation is based are highlighted. The simulations show strong wave diffraction effects for inhomogeneous dump structures, resulting in smaller displacements in near-surface areas of the slope. Further it was found that large areas of the dump show a temporary decrease of effective stress. The initial strong differences in stiffness between the different materials may decrease with time after several seismic events due stress redistributions caused by earthquakes.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Yuanzheng Lin, Zhouhong Zong, Shizhu Tian, Jin Lin〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Most current baseline correction methods for near-fault ground motion records focus on eliminating and minimizing baseline errors and obtaining true ground motion records that are in accordance with GPS-measured coseismic displacements. Though these methods can recover true ground motions, the single value of ground permanent displacement cannot meet the requirement of seismic response analysis of fault-crossing bridge with the consideration of various levels of relative static displacements. Besides, the corrected final displacements are often too large which will cause an extremely large pseudo-static response and a relatively small dynamic response in bridge structures. To provide across-fault seismic excitations with a reasonable series of final displacements, a new baseline correction scheme based on the target final displacement is proposed in this study, in which an additional offset displacement is introduced based on the Iwan correction scheme. The new baseline correction scheme aims at modifying the pseudo-static displacement of ground motion records to facilitate the agreement between the achieved final displacement and the target final displacement. The correction scheme is then examined in three aspects including time histories, response spectra and bridge responses. The analysis results indicate that sets of the corrected time history records with a large range of final displacements can be well achieved with a minor influence on spectral characteristics. The seismic response analysis of a cable-stayed bridge crossing a dip-slip fault-rupture zone shows that the pseudo-static response can be controlled, meanwhile, the dynamic response remains almost intact by using the new baseline correction scheme. This work can be used as a reference for input excitations of bridge crossing fault-rupture zones.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Xinzheng Lu, Lei Zhang, Yao Cui, Yi Li, Lieping Ye〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Recently, seismic resilience has become a research frontier in civil engineering. The self-centering steel frame can effectively control structural damage and reduce structural residual deformation, which ensures rapid repair after an earthquake. Therefore, such a structural system has attracted extensive attention from researchers. One of the important research directions on self-centering steel frames is the development of high-performance energy-dissipating components. A new type of dual-functional replaceable stiffening angle steel (SAS) component is proposed here. It can effectively improve the stiffness and strength of beam-column connections and has sufficient energy-dissipating performance and ductility. Seven different energy-dissipating components were tested, including one angle steel component and six SAS components. The strength and deformation capacity of the components were compared based on monotonic loading tests. The SAS component with the highest out-of-plane stability and sufficient strength and initial stiffness was selected and subsequently tested under hysteretic loading to investigate its energy-dissipating performance. The theoretical analysis methods of the initial stiffness and the yield moment provided by the SAS components were proposed and validated by the finite-element (FE) models calibrated using experimental data.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Christos Giarlelis, Jared Keen, Evlalia Lamprinou, Victoria Martin, Gerasimos Poulios〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The recently constructed Stavros Niarchos Foundation Cultural Center (SNFCC), houses the National Opera and the National Library of Greece. In order for the structural design to meet the demanding architectural requirements as well as the high-performance seismic specifications that were set, a seismic isolation system was incorporated. SSI effects due to poor silty sands were an additional challenge. After presenting the design parameters and the choice of seismic isolation type, the paper focuses on the methodology for the seismic design. This, performed in three consecutive stages, includes simple analyses using single-degree of freedom model for initial scheming, dynamic response spectrum analyses for detailed design and non-linear time history analyses using two sets of selected earthquake records, semi-artificial and real ones, for verification of the response. The results demonstrate a good correlation between different analysis techniques and provide a valuable insight into the behaviour of two complex, seismically isolated structures under seismic loads. The problems and solutions resulting from the implementation of the seismic isolation are also briefly presented.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): Joonsang Park, Amir M. Kaynia〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, we introduce and discuss features and improvements of the well-established stiffness matrix method that is used in simulation of wave propagation in layered media. More specifically, we present stiffness matrices for an acoustic layer and a vertically transverse isotropic (VTI) viscoelastic soil layer. Combining these stiffness matrices enables a straightforward technique for modeling of acousto-elastic wave propagation in layered infinite media. In addition, we propose a technique to simulate discontinuity seismic sources, which was not used earlier in the context of the stiffness matrix method. Finally, we propose a framework to derive a key parameter of the absorbing boundary domain technique Perfectly Matched Layer (PML). Numerical examples are presented in order to help understanding the features and improvements discussed in the study from the fields of geophysics and soil dynamics. It is believed that the features and improvements discussed herein will make the application of the stiffness matrix method even wider and more flexible.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): Amin Rahmani, Mahdi Taiebat, W.D. Liam Finn, Carlos E. Ventura〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the current state of practice, static/seismic soil-pile interaction is included in design calculations by a set of one-dimensional (1D) uncoupled springs. The guidelines of American Petroleum Institute (API) are often adopted to develop backbone curves for the lateral springs. The purpose of the paper is to assess the reliability of this practice. Twenty-seven static field and laboratory tests, and two dynamic centrifuge tests are simulated to evaluate the performance of the springs. More detailed elaboration on the performance of the springs is provided by simulation of one of the static tests and both of the dynamic tests using also three-dimensional (3D) continuum approach. The evaluation results indicate that API springs do not capture the major mechanisms involved in soil-pile interaction, and this results in erroneous estimation of pile deflections and bending moments. It is shown that the observed errors stem not only from the insufficient characterization of the spring properties (API backbone curves), but also from the inadequate simulation method in which three-dimensional continuum configuration of the supporting soil is represented by a 1D uncoupled spring.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): Sajad Veismoradi, Amirhossein Cheraghi, Ehsan Darvishan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Buckling-Restrained Braced Frames (BRBFs) are among the common seismic resistant systems with many beneficial characteristics such as stable cyclic behavior and high energy dissipation. However, recent studies have shown that BRBFs are susceptible to residual deformations during earthquakes which makes them vulnerable to aftershock events. The aim of the current study is to investigate the aftershock collapse capacity of BRBFs. In the first part of the paper, simplified procedures including IDA and collapse fragility analyses are carried out to gain more insight regarding the residual drift and collapse capacity of the intact frames. Then, aftershock fragility assessment is conducted for several damage states, to highlight the influence of post-mainshock residual drifts on the collapse of the structures. As for the second part, a detailed probabilistic framework is introduced and utilized to include the effects of upcoming aftershocks on the annual collapse probability of the structures. Results show that aftershock can highly intensify the structural response especially when the structure tolerates large residual drifts during the mainshock.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 31 October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering〈/p〉 〈p〉Author(s): Montaser Bakroon, Reza Daryaei, Daniel Aubram, Frank Rackwitz〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The buckling of steel pipe piles during installation is numerically studied. Generally, numerical simulation of installation processes is challenging due to large soil deformations. However, by using advanced numerical approaches like Multi-Material Arbitrary Lagrangian-Eulerian (MMALE), such difficulties are mitigated. The Mohr-Coulomb and an elastic-perfectly plastic material model is used for the soil and pile respectively. The pile buckling behavior is verified using analytical solutions. Furthermore, the model is validated by an experiment where a pipe pile is driven into sand using vibratory loading. Several case scenarios, including the effects of heterogeneity in the soil and three imperfection modes (ovality, out-of-straightness, flatness) on the pile buckling are investigated. The numerical model agrees well with the experimental measurements. As a conclusion, when buckling starts, the penetration rate of the pile decreases compared to the non-buckled pile since less energy is dedicated to pile penetration given that it is spent mainly on buckling.〈/p〉〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 116〈/p〉 〈p〉Author(s): Payam Sotoudeh, Mohsen Ghaemian, Hamid Mohammadnezhad〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Seismic analysis of complex structures such as concrete dams has been the subject of numerous studies. One of the challenges in seismic analysis of such systems is proper modelling of massed foundation. Since concrete dams’ foundations are usually layered, this makes the homogenous half-space assumption relatively unrealistic. In this paper, the effects of massed layered foundation on seismic response of concrete gravity dams in dam-reservoir-foundation systems are investigated. Seismic finite element analysis of the system carried out using domain reduction method. This approach is compared with another available method named, free-field column. First set of analysis considers the effect of modular ratio between layers on seismic response of the gravity dam. Second set of analyses investigate the effects of layers’ geometry, location and orientation on obtained responses. Results highlight the considerable effects of massed layer foundation assumption against its homogenous counterpart. Besides, results show that layer properties dictate how severely they can affect the dynamic responses of the dam.〈/p〉〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 116〈/p〉 〈p〉Author(s): Prajakta R. Jadhav, Amit Prashant〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A double wedge model has been proposed to compute seismic sliding displacements of cantilever retaining walls. Experimental observations indicate formation of rupture planes in the form of an inverted triangular wedge in the backfill of retaining walls. Computation of critical yield acceleration at each time instant considering the v-shaped weakest rupture planes which evolve during the ground motion is the preliminary aim of the double wedge model. The model computes translational displacements considering the relative movement of soil wedge along these rupture planes. It considers velocity compatibility along with the acceleration compatibility between the wall and soil wedge. It also computes approximate depth of subsidence of the backfill soil during ground motion. A simplified double wedge model has been also considered wherein the yield acceleration at all time instants is computed with respect to a fixed wedge. The double wedge model and its simplified version have been compared with different cases studies, which show the seismic sliding displacements matching well with the real measurements.〈/p〉〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 116〈/p〉 〈p〉Author(s): Wang Hai-tao, Shen Jiayu, Wu Feng, An Zhiqiang, Liu Tianyun〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Combined with the plasticity - damage constitutive model of hydraulic concrete obtained from the test by considering the strain rate effect, the elastic-plastic numerical simulation of Koyna concrete gravity dam under different seismic waves is carried out with ABAQUS software. The effect of strain rate on the dynamic performance of concrete gravity dam under earthquake is discussed by comparing the results of high strain rate and quasi-static loading. The results show: when the peak acceleration is small, the acceleration and displacement of the feature point calculated by considering the strain rate effect are smaller than those without considering the strain rate effect, and the difference is not obvious. With the increase of the seismic peak acceleration, the difference gradually increases. Considering the effect of concrete strain rate, the principal tensile stress in the dam is higher than without considering the strain rate, and more in accordance with the actual damage form. It is suggested that the strain rate effect of concrete should be considered in the seismic response analysis of concrete gravity dam.〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 117〈/p〉 〈p〉Author(s): Elisabetta Cattoni, Diana Salciarini, Claudio Tamagnini〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In recent years, much attention has been paid to performance–based design of flexible retaining structures, focusing on the evaluation of the permanent deformations of the soil–structure system caused by given seismic loads, rather than on the assessment of conventional safety factors determined by comparing seismic actions and system resistance (typically based on limit equilibrium methods). While only a few examples of fully coupled, dynamic numerical simulations of flexible retaining structures adopting advanced cyclic/dynamic models for soils can be found in literature, a number of recent works have proposed simple modifications of the classical Newmark method to assess the permanent displacements of the structure at the end of the seismic excitation. Most of the aforementioned works refer to cantilevered diaphragm walls, for which the failure mechanisms at limit equilibrium are relatively simple to describe. However, this is not the case for anchored or propped flexible structures, where the velocity field at failure under a pseudo–static seismic load is quite complex and can be affected by the plastic yielding of the wall upon bending. In this work, upper– and lower–bound limit analysis FE solutions are used as a basis for the development of a Generalized Newmark Method, based on the accurate evaluation of the critical accelerations for the retaining structure and the corresponding failure mechanisms. It can be shown that, under two reasonable simplifying assumptions, a Newmark–like scalar dynamic equation of motion can be derived which, upon double integration in time, provides the magnitude of the permanent displacements associated to each failure mechanism, as provided by limit analysis. This procedure allows the reconstruction of the full permanent displacement field around the excavation, not just the evaluation of horizontal soil movements at selected points. The application of the method to a number of selected prototype excavations demonstrates the potentiality of the proposed approach, which can be extended easily to other complex geotechnical structures.〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 117〈/p〉 〈p〉Author(s): Marco Furinghetti, Alberto Pavese, Virginio Quaglini, Paolo Dubini〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉In the present work the experimental response of the Curved Surface Slider (CSS) is investigated through an experimental campaign, carried out on a full-scale prototype subjected to both unidirectional and bidirectional tests. The aim of the study is to assess the effect of vertical load, speed and sustained motion on the frictional response of the device and to compare results returned by different displacement trajectories. In order to perform a quantitative evaluation, a mathematical expression to model the decay of the coefficient of friction as a function of energy dissipation is proposed and calibrated upon experimental data.〈/p〉 〈p〉Though at low vertical load non-negligible discrepancies between unidirectional and bidirectional orbits were noticed, the CSS device shows consistent behaviour as the applied load, and consequently the dissipated energy, are increased. The results allow to draw some guidance for the estimation of the design variation range of the friction coefficient of Curved Surface Slider devices used to perform bound analyses.〈/p〉 〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 117〈/p〉 〈p〉Author(s): Yuan Yao, Jie Chen, Tao Li, Bo Fu, Haoran Wang, Yuehua Li, Hailiang Jia〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Soil liquefaction is a type of coseismic hydrological change triggered by earthquakes, and its occurrence results in major property damage and casualties. The dynamics of coseismic hydrological changes are not fully understood. In order to address this, we studied coseismic deformations such as liquefaction and ground fissures that occurred as a result of strong seismic activity during the 2016 Mw6.6 Akto earthquake, which took place in the interior of the Pamir Plateau in northwestern China. This paper presents a systematic survey of the frozen soil liquefaction and ground fissures caused by this earthquake. The majority of liquefaction sites near the Karaat River are located on the T1 terrace, in Bulake village, and are adjacent to the alluvial fan of the Kungai Mountain. We find that the liquefaction was caused by the original spring and coseismic ground fissure during the earthquake. Approximately 80% of the liquefaction sites are formed along the original spring in the epicenter. The maximum height of sand boils is 15 cm. The remaining 20% of the liquefaction sites are formed along the coseismic ground fissure. Our results suggest that the frozen soil layer impedes liquefied material in the lower unfrozen soil layer from reaching the surface, and the material formed from liquefaction is consequentially channeled through the primary fault and coseismic ground fissures. Liquefaction associated with the Akto earthquake demonstrates the importance of accounting for the possibility of a series of coseismic geological disasters, such as soil liquefaction and ground fissures, in areas with similar geology, altitude, and temperature.〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 117〈/p〉 〈p〉Author(s): Li Zhang, Mingzhou Su, Chao Zhang, Hua Shen, Md Mofakkharul Islam, Ruifu Zhang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The traditional design method of the elastic response reduction curve (ERRC) was used to design the parameters of the viscoelastic damper (VED), where the plastic behavior of the primary structure is neglected. Considering the structural plastic behavior, in this study, a direct design method is proposed to obtain the parameters of VEDs based on the elastic-plastic response reduction curve (EPRRC), which can illustrate the relationship between damper parameters and the response reduction effect in the elastic-plastic stage. First, the ERRC is developed to the EPRRC, and the differences between them are compared using the displacement and acceleration response difference ratios, which demonstrate an overestimated response reduction effect of VEDs in the elastic-plastic stage using the ERRC. Then, the corresponding design procedures are given based on the EPRRC by referring to the direct displacement-based design theory. Finally, a benchmark model is used to illustrate the effectiveness of this proposed design method by conducting a time history analysis. The analysis results indicate that the target story drift of the structure can be satisfied under different earthquake intensities using VEDs. Thus, based on this study, the development of the EPRRC can be considered worthwhile, and the proposed design method of VED parameters is easy to implement and is effective.〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 117〈/p〉 〈p〉Author(s): G. Kampas, J.A. Knappett, M.J. Brown, I. Anastasopoulos, N. Nikitas, R. Fuentes〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Major seismic events have shown that tunnels in cohesionless soils may suffer extensive seismic damage. Proper modelling can be of great importance for predicting and assessing their seismic performance. This paper investigates the effect of lining structural modelling on the seismic behaviour of horseshoe-shaped tunnels in sand, inspired from an actual Metro tunnel in Santiago, Chile. Three different approaches are comparatively assessed: elastic models consider sections that account for: (a) linear elastic lining assuming the geometric stiffness; (b) linear elastic lining matching the uncracked stiffness of reinforced concrete (RC); and (c) nonlinear RC section, accounting for stiffness degradation and ultimate capacity, based on moment-curvature relations. It is shown that lining structural modelling can have major implications on the predicted tunnel response, ranging from different values and distributions of the lining sectional forces, to differences in the predicted post-earthquake settlements, which can have implications on the seismic resilience of aboveground structures.〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 117〈/p〉 〈p〉Author(s): Ruifeng Liu, Zheming Zhu, Meng Li, Bang Liu, Duanying Wan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Dynamic fracture behavior under impacting loads has been well studied, but for that under blasting loads, less attention has been paid. In order to investigate mode I crack propagation behavior of brittle materials under blasting, a new configuration specimen, i.e. single internal crack circular disc (SICCD) specimen was proposed in this paper, and it was applied in the blasting experiments. Crack propagation gauges (CPGs) were stuck along crack propagation paths to measure crack initiation and propagation time and crack propagation speeds. Green sandstone and PMMA were selected to make the SICCD specimens. Finite difference models were established by using AUTODYN code according to the SICCD specimen dimension and the loading curve measured near the borehole. Generally, the simulation results of crack propagation paths agree with the test results. Finite element code ABAQUS was applied in the calculation of dynamic stress intensity factors (SIFs), and the curves of dynamic SIFs versus time were obtained. By using these curves and the breaking time of the CPG wires, the mode I critical dynamic SIFs in initiation and in propagation were obtained. The results show that the measuring method of the critical dynamic SIFs of brittle materials under blasting presented in this paper is feasible and applicable. During crack propagations, the crack speed is not a constant, and the critical dynamic SIFs in propagation decreases with the increase of crack propagation speeds.〈/p〉〈/div〉

Description: 〈p〉Publication date: March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 118〈/p〉 〈p〉Author(s): Zhang Zhi, Li Xiaojun, Lan Riqing, Song Chenning〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Focusing on a small radius curved bridge, a serious of shaking table tests and corresponding numerical finite element analyses were conducted for a 1/16 scaled curved bridge model considering SSI (Soil-Structure Interaction) effect. In the testing and simulating, the strong motion records with different frequency characteristics and durations, El Centro record from Ms6.7 Imperial Valley earthquake and Wolong record from Ms8.0 Wenchuan earthquake, were as the input motions. The dynamic property, vibration response, damage rule, and failure mode of the curved bridge were obtained preliminarily. The experimental results showed that the transverse stiffness of this soil-pile-bridge structure system was larger than the longitudinal stiffness; the obvious torsion effect of the model structure was observed in the tests under the input motion in uni-direction, and the larger was the input motion PGA, more obvious was the torsion effect; the seismic responses were more sensitive to input motions with relative low-frequency components; the damage degree of the pier bottom increased from short to high pier, and the rubber bearings at side piers appeared two different failure modes induced by the longitudinal slope. Compared with straight bridges, the curvature radius made curved bridges more prone to causing rotation and displacement. Furthermore, finite element analyses were conducted by using the plastic-damage model for concrete, and equivalent soil springs method for pile-soil interaction, respectively. The simulations were in agreement with the test results satisfactorily, moreover the differences between these results were discussed in detail and the errors were in an acceptable range. These studies would be used to provide insights for the further research and theoretical design of curves bridges.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 23 February 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering〈/p〉 〈p〉Author(s): Hiroshi Kawase, Fumiaki Nagashima, Kenichi Nakano, Yuta Mori〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Horizontal-to-Vertical spectral ratios of microtremors (MHVR) have been utilized as a convenient tool to extract a predominant frequency at a target site. The so-called “Nakamura” method, which was proposed by Nakamura in 80's, assumed that MHVR provides us directly the S-wave amplification factor of earthquake in the horizontal component, that is, Horizontal-to-Horizontal spectral ratio (HHR) with respect to the bedrock, although the validity of the method had never been proved. Recently, based on the diffuse field concept (DFC) proposed by Sánchez-Sesma and others in 2011 MHVRs are found to correspond to the square root of the ratio of the imaginary part of the displacement for a unit harmonic load in the horizontal direction with respect to the corresponding one in the vertical direction. With the same DFC for body waves Horizontal-to-Vertical spectral ratios of earthquake (EHVR) correspond to the ratio of the horizontal motion for a vertical incidence of S wave with respect to the vertical correspondent of P wave, as revealed by Kawase and others in 2011. Thus there should be a systematic difference between EHVR and MHVR because of the difference in their primary contribution of wave types. We first calculated the ratios of EHVR with respect to MHVR (EMR) at 100 strong motion stations in Japan. Then we normalized frequency by the fundamental peak frequency at each site and calculated the average of EMRs for five categories based on their fundamental peak frequencies. Once we got empirical EMRs for five categories we transformed MHVRs into pseudo EHVRs. At the same time we calculated the average Vertical-to-Vertical spectral ratios (VVRs) for the same sites using the generalized spectral inversion technique (GIT) of Nakano et al. (2015) [16]. Finally the S-wave amplification factor, HHR, of earthquake ground motion at the site were calculated from MHVR with double corrections using EMR and VVR for the corresponding category. We compared these final empirical prediction with the observed HHRs from GIT to find quite high correlations and small overall residuals. The proposed method to get HHR from MHVR with these double empirical corrections can be considered as a natural but significant extension to the so-called “Nakamura” method.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 21 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering〈/p〉 〈p〉Author(s): Xiao Wei, Jun Yang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The liquefaction resistance of silty sands and the potential effect of initial static shear stress are major concerns in seismic design of dams and embankments. This paper presents a systematic experimental study on non-plastic silty sands to address these concerns. It is shown that the concept of threshold 〈em〉α〈/em〉 (〈em〉α〈/em〉〈sub〉th〈/sub〉) proposed by Yang and Sze (2011) to characterize the impact of 〈em〉α〈/em〉 (representing the initial static shear stress level) on cyclic resistance (〈em〉CRR〈/em〉) of clean sands is applicable to silty sands as well. When 〈em〉α〈/em〉 〈 〈em〉α〈/em〉〈sub〉th〈/sub〉, 〈em〉CRR〈/em〉 increases with increasing 〈em〉α〈/em〉, otherwise it decreases with increasing 〈em〉α〈/em〉. The threshold 〈em〉α〈/em〉 is affected by the initial packing density, the initial effective confining pressure and the fines content. An improved state dependency of the threshold 〈em〉α〈/em〉, which is regardless of fines content, is proposed in the framework of critical state soil mechanics by using the state parameter (〈em〉ψ〈/em〉). An analysis platform, known as 〈em〉CRR〈/em〉-〈em〉ψ〈/em〉 platform and developed based on clean sand data, is shown to have the capability of characterizing the state dependence of 〈em〉CRR〈/em〉 for sands with varying fines contents. This platform in conjunction with the unified 〈em〉α〈/em〉〈sub〉th〈/sub〉-〈em〉ψ〈/em〉 correlation provides a unified and consistent framework for understanding the complicated effects of initial static shear stress on soil liquefaction and for quantifying such effects for engineering practice.〈/p〉〈/div〉

Description: 〈p〉Publication date: March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 118〈/p〉 〈p〉Author(s): Jun Wang, Zhi Zhou, Xiuqing Hu, Lin Guo, Yuanqiang Cai〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Soft clay is subjected to complex cyclic stress paths involving a combination of cyclic vertical and horizontal stress with principal stress rotation caused by traffic load. In this study, three groups of tests, namely tests with principal stress rotation, cyclic confining pressure, and combination of principal stress rotation and confining pressure, were conducted at different load frequencies using Wenzhou soft clay with hollow cylinder apparatus to investigate the undrained cyclic behavior of soft clay. The development of pore water pressure, accumulative strain, axial stress–strain relationship, and resilient modulus were analyzed. Experimental results show that the different stress paths play important roles in the cyclic behavior. The principal stress rotation accelerates the degradation of the resilient modulus due to the accumulation of axial strain. The cyclic confining pressure constrains the development of axial strain, which results in a larger resilient modulus. A lower load frequency results in a larger pore water pressure, accumulative strain, and degradation of resilient modulus. These results provide reference for the assessment of settlement induced by traffic load on soft soils.〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 117〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 118〈/p〉 〈p〉Author(s): Jiulin Bai, Shuangshuang Jin, Junxian Zhao, Bohao Sun〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Endurance time (ET) method is a new approach for assessing the seismic performance of structures. This paper investigated the effectiveness and accuracy of employing ET method to predict the seismic response of soil-structure-interaction (SSI) system. The Chinese code-conforming endurance time acceleration functions (ETAFs) were firstly generated. Two 5- and 10-story reinforced concrete (RC) frame structures were employed as prototype structures. The finite element model of soil-foundation-structure was established based on nonlinear Beam-on-Nonlinear-Winkler-Foundation (BNWF) theory. Nonlinear dynamic analyses of the structural systems subjected to 3 ETAFs and 22 ground motions were carried out. The seismic response of superstructure and foundations, and different SSI models were compared. The results indicate the ET method can predict the seismic response of SSI structural systems, with a high efficiency and accepted accuracy.〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 117〈/p〉 〈p〉Author(s): Luis A. Pinzón, Luis G. Pujades, Albert Macau, Sara Figueras〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, previous microzonation studies in Barcelona (Spain) were revisited, and available data on the predominant periods of soils in the city were compiled to develop an updated microzonation map of the city. In addition, the building database was updated and used to create a map of building fundamental periods. The crossing of soil predominant period and building fundamental period maps led to the detection of areas in which resonance phenomena and, indeed, increased amplification of the structural response are expected. Thus, zones of Barcelona were identified in which the seismic hazard is probably greater due to resonance effects. The improved microzonation maps and the detection of soil-building resonance areas contribute significantly to enhanced precision and awareness of seismic hazard and risk in Barcelona.〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 117〈/p〉 〈p〉Author(s): Yang Ding, George P. Mavroeidis, Nikos P. Theodoulidis〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The 1995 〈em〉M〈/em〉〈sub〉w〈/sub〉 6.5 Kozani-Grevena earthquake struck an area in northwestern Greece characterized by relatively low seismicity based on historical information and instrumental data. The ground shaking in the near-fault region was recorded by a strong-motion accelerograph in the city of Kozani, at a distance of about 23 km from the epicenter. In this article, broadband ground motions are generated at selected locations and at a dense grid of observation points extending over the causative fault of the 1995 Kozani-Grevena earthquake using a hybrid deterministic-stochastic method. Based on a multi-segment fault model with curved geometry proposed in the literature, the low-frequency components of the synthetic ground motion are simulated using the discrete wavenumber representation method and the generalized transmission and reflection coefficient technique. The high-frequency components of the synthetic ground motion are generated using the stochastic modeling approach and the specific barrier model. The two independently derived ground-motion components are then combined using matched filtering at a crossover frequency of 1.2 Hz to generate broadband ground-motion time histories and response spectra. The simulation results are validated by comparing the synthetic ground motions with the recorded ones in the city of Kozani and with estimates of peak ground-motion quantities inferred from ground-motion prediction equations.〈/p〉〈/div〉

Description: 〈p〉Publication date: March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 118〈/p〉 〈p〉Author(s): Gopala Krishna Rodda, Dhiman Basu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper explores the possibility of a new parametric representation of auto-spectral density (ASD) that enables extraction of several meaningful insights. Recorded translational ground motions are considered first and the resulting parametric model is capable to address the scenario when seismic energy is distributed over multiple frequency bands. A slightly different form is developed to address the rotational ground motion. Variation of ASD over the footprint of seismic arrays, both large (SMART1) and dense (LSST), is studied. The assessment is based on spectral similitude using spectral contrast angles and distance correlation. Possible correlation of the parameters of the proposed ASD model against site and event characteristics is investigated based on selected ground motions from PEER database. Model parameters thus computed are used in synthetically predicting the ASD of ground motions at the LSST array and that shows good resemblance against the recorded events.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 17 February 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering〈/p〉 〈p〉Author(s): M. Abdullah Sandıkkaya, Sinan Akkar, Pierre-Yves Bard〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We introduce a site factor computation method for a region by extending the site-specific and probabilistic site amplification approach in Bazzuro and Cornell (2004). The site-factor exceedance probability is estimated from the exceedance probabilities of the reference rock ground motion and the soil amplification conditioned on the reference rock ground motion. The former probability is represented by regional hazard curves. The latter probability is computed from soil amplification models. The proposed method is capable of yielding site factors for a target exceedance probability. This property does not exist in the current code-based site factors. Given a site class, if the site factors and the reference rock spectrum possess the same exceedance probability the resulting spectrum would have the same probability of exceedance. The use of such probabilistically consistent earthquake demands would be more relevant for probability-based seismic design and assessment. Owing to the use of hazard curves, the proposed method can account for regional seismicity in the computation of site factors.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 17 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering〈/p〉 〈p〉Author(s): Jorge Ruiz-García〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A discussion on the paper by Ji et al. [1] is presented. The paper is focused on the evaluation of residual displacement ratios, named 〈em〉C〈/em〉〈sub〉〈em〉r〈/em〉〈/sub〉, of single-degree-of-freedom (SDOF) systems subjected to a set of 120 earthquake ground motions recorded at site class E according to the FEMA 450 [2] document published in the United States. Based on their results, the authors introduced a predictive equation to obtain estimates of mean 〈em〉C〈/em〉〈sub〉〈em〉r〈/em〉〈/sub〉. This paper discusses its main results and the proposed equation in the light of previous published research on the subject.〈/p〉〈/div〉

Description: 〈p〉Publication date: March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 118〈/p〉 〈p〉Author(s): S. Soltanieh, M.M. Memarpour, F. Kilanehei〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Highway bridges with piers of unequal height crossing irregular topographical surfaces have potential complexities in terms of component vulnerability evaluations. This paper investigates the seismic behavior of a five-span concrete girder bridge with three coefficients of pier height and two different types of irregular configurations. Moreover, soil-structure interaction is taken into account by modeling a typical deep foundation, including piles and the surrounding soil, in order to examine the effect of pier base flexibility compared to the equivalent fixed-base model. For this purpose, incremental dynamic analyses are performed on the three-dimensional analytical finite element models using a set of ground motion pairs each rotated about the vertical axis of bridge producing seven angles of seismic incidence. The results obtained from the dynamic analyses and fragility assessment of the selected bridge models illustrate that substructure irregularity, support condition of piers, and directionality of seismic excitations are three interdependent factors in vulnerability assessment of highway bridges. Variation in each of the above-mentioned factors leads to change in the fragility characteristics of a bridge at global system failure mode or individual component limit states.〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 117〈/p〉 〈p〉Author(s): Yan Zhuang, Kang-Yu Wang, Hua-Xiang Li, Meng Wang, Liang Chen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Shakedown analysis is a robust approach to solve the strength problem of a structure under cyclic or repeated loading, e.g. railway structure subjects to rolling and sliding loads. A three-dimensional analytical shakedown solution is developed in this paper for the strength analysis of cohesive-frictional materials under multiple Hertz loads, which is then applied into the shakedown analysis of railway structure. Different to the pavement, the railway structure subjects to multiple wheel loads acting on the surface of two parallel rails, and then transformed to the substructure, which leads to different elastic and residual stress fields. For the application of Melan's shakedown theorem, the residual stress field in railway strucuture is rationally simplified to find the most critical plane that influence the most on the shakedown limit. The elastic stresses is then analytically derived for a single layer half-space under multiple Hertz loads, and is obtained numerically by means of the finite element technique for the multi-layered railway structure. Finally, the shakedown limit can be obtained in a direct way. Parametric study indicates how wheel loads, material properties such as frictional coefficient, friction angle and Poisson's ratio, and multi-layers influence the shakedown limit and stability condition of railway structure. It is found that the shakedown load increases with the increase of cohesion ratio, ballast frictional angle, and thickness ratio. However, the increase of the shakedown load ceases once the failure location moves from ballast layers to sub-ballast layers. This indicates that there is an optimum combination of material properties and layer thickness which provides the maximum resistance to the train loads. The obtained results give a useful reference for the engineering design of the railway structure.〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 117〈/p〉 〈p〉Author(s): B.W. Maurer, R.A. Green, S. van Ballegooy, L. Wotherspoon〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Utilizing an unprecedented database of field and laboratory test data from Christchurch, New Zealand, this study develops deterministic and probabilistic correlations relating the soil behavior type index (〈em〉I〈/em〉〈sub〉〈em〉c〈/em〉〈/sub〉) to laboratory test-based liquefaction susceptibility and fines content. The proposed 〈em〉I〈/em〉〈sub〉〈em〉c〈/em〉〈/sub〉 correlations are in turn used to assess liquefaction hazard for 9623 case studies compiled from three earthquakes that impacted Christchurch, New Zealand, wherein the predicted liquefaction severity is compared to post-earthquake field observations. Furthermore, the accuracy of the predictions based on the region-specific 〈em〉I〈/em〉〈sub〉〈em〉c〈/em〉〈/sub〉 correlations are compared to those made using generic 〈em〉I〈/em〉〈sub〉〈em〉c〈/em〉〈/sub〉 correlations. The use of the Christchurch-specific 〈em〉I〈/em〉〈sub〉〈em〉c〈/em〉〈/sub〉 correlations, in general, only slightly improved the liquefaction severity predictions. These findings could be a result of shortcomings in the procedures used to predict liquefaction triggering and/or liquefaction manifestations. Nevertheless, the findings give credence to the use of generic correlations for typical projects. Finally, the overall framework of the study used herein can be applied to worldwide locals and is not just limited for use in the Canterbury region of New Zealand.〈/p〉〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 116〈/p〉 〈p〉Author(s): George Papathanassiou, Sotiris Valkaniotis, Spyros Pavlides〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The earthquake Mw6.6 (macroseismic intensity VIII, ESI-07 scale) that occurred on July 20, 2017 at 22:31 UTC (01:31 local time) in Gökova Bay, SE Aegean Sea, induced minor damages to contemporary structures at the island of Kos, Greece, while severe damages were reported on Venetian and Ottoman-era constructions, causing two deaths. Focusing on the island of Kos, secondary effects were reported in the eastern part, including liquefaction-related phenomena and tsunami. The generation of the latter one indicates the likelihood to this type of effects in the Aegean Sea. Liquefaction-induced lateral spreading caused severe structural damages at the waterfront area of the city of Kos. This area was investigated in detail few days after the event, by performing field measurements using a surveyor's tape and additionally, by applying SfM-based technique using a ground-based digital camera. The values of horizontal deformation, measured by these two techniques are in agreement, while on vertical axis a deviation of 12% is resulted.〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 117〈/p〉 〈p〉Author(s): D. Farahani, F. Behnamfar, H. Sayyadpour, M. Ghandil〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The problem of seismic impact between torsionally coupled multi story moment frame buildings is investigated in this paper. Five pairs of adjacent structures spaced at various separation distances are considered. The buildings are 4–10 stories in height. Although a common plan being symmetric with regard to lateral stiffness is considered, a mass eccentricity variable from zero to 30% of the plan dimension is assumed. By three-dimensional modeling of the nonlinear torsional buildings having common story elevations, the seismic pounding happen anywhere along the adjacent buildings edges. Effect of impact and torsional eccentricity are studied by comparison of nonlinear dynamic responses of buildings at different clear distances under 11 consistent earthquakes. The responses include pounding forces at stories, story drifts, story shears and plastic hinge rotations. It is shown that how pounding incidents increase for larger eccentricities and how pounding occurs even at the clear distances prescribed by seismic design codes. The combined effect of torsional eccentricity and pounding results in amplifying the nonlinear response of structure especially for the peripheral frames.〈/p〉〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 116〈/p〉 〈p〉Author(s): Miad Saberi, Charles-Darwin Annan, Jean-Marie Konrad〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, an implementation of an advanced two-surface plasticity interface constitutive model in a general-purpose finite element code ABAQUS for application in soil-structure interaction problems under static and dynamic loading conditions is presented. A recently developed constitutive model by the authors for gravelly soil-structure interface was improved to simulate the behavior of both gravelly and sandy soil-structure interfaces. A new failure surface was introduced into the model in order to simulate the softening behavior of interfaces under monotonic and cyclic loading. The constitutive model was then implemented in ABAQUS as a thin-layer interface element to demonstrate its capabilities in representing the complex behavior under different stress paths and normal stresses, including debonding and rebonding mechanisms at interface zones. The accuracy and robustness of the numerical implementation algorithm was examined by considering the effect of time step size, and by simulating different boundary value problems. The numerical predictions under different loading and boundary conditions were compared with experimental observations.〈/p〉〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 116〈/p〉 〈p〉Author(s): Hongjing Li, Michael J. O’Rourke〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉It is recognized that seismic damages to segmented buried pipelines depend in part upon transient ground strain due to seismic wave propagation. Such wave propagation damage seems to be larger at sites with variable subsurface conditions, because of drastic changes in seismic wave characteristics as they propagates in heterogeneous rock and soil layers. This paper intends to investigate the amplification of horizontal ground strains in a valley subjected to vertically incident SH waves. A 2D model with an inclined soil-rock interface is established to simulate conditions of the valley subject to seismic wave propagation. A procedure for evaluating the ground strain amplification is developed by consideration of travel path effects. Three amplification/de-amplification mechanisms are specifically considered, the ground velocity amplification, ground strain amplification due to the change in the propagation direction, and de-amplification due to a lack of total reflection at the soil-rock interface. The analysis results show that the maximum amplification factor is mainly affected by the interface inclination angle and shear wave velocity ratio between the valley soil and the base rock. For a given number of wave cycles, the amplification factor grows with the increment of the inclination angle and declines with the growth of shear wave velocity ratio. The de-amplification at inclined interface is likely to nullify the amplification generated by travel path effects.〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 117〈/p〉 〈p〉Author(s): Shiping Zhang, Chunyi Cui, Gang Yang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper we develop a simplified analytical solution for the impedance function of viscoelastic pile groups partially embedded in a layered, transversely isotropic, liquid-saturated, viscoelastic soil medium under a vertical time-harmonic load. In developing our solution, we use the porous medium model established by de Boer to describe the soil and the Rayleigh–Love rod model to describe the pile groups. To obtain the vertical impedance function of the pile groups, based on a “two pile model” consisting of an active pile and a passive pile, we first get a displacement attenuation function and shearing forces to piles of the soil by using a separation method of variables to solve motion equations for the soil. Second, using this displacement attenuation function and shearing forces, we derive a dynamic interaction factor of pile to pile. Then, by means of the dynamic interaction factor and a superposition principle, we obtain the vertical impedance function of the pile groups. We validate our model by comparing it to the reported results of purely elastic soils. Finally, we conduct numerical examples obtained from our model to show the effects of main parameters, such as the non-embedded length of piles, the transversely isotropic parameter of soils, and the liquid–solid coupled coefficient of soils on the vibration characteristics of a typical pile group. From these analyses, we conclude that the dynamic interaction factors of pile to pile for single-phase soils suggested by Dobry and Gazetas are not suitable for the vibration problems of pile groups in saturated soils. Thus, it is necessary to present corresponding dynamic pile–pile interaction factors for such problems. Moreover, the non-embedded length of piles, the transversely isotropic parameter of soils, and the liquid–solid coupled coefficient of soils have noticeable effects on the dynamic impedance of pile groups, which is valuable for pile foundation designs.〈/p〉〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 116〈/p〉 〈p〉Author(s): Lisa M. Star, Salih Tileylioglu, Michael J. Givens, George Mylonakis, Jonathan P. Stewart〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We describe procedures to evaluate the dynamic properties of test structures subject to forced vibration testing. We seek modal vibration periods and damping ratios corresponding to the actual flexible-based response of the structure (incorporating the effects of compliance in the soil medium supporting the foundation) and similar attributes for a fixed-base condition in which only the flexibility of the structure is represented. Our approach consists of using suitable input and output time series with conventional parametric system identification procedures, and as such extends previously developed procedures for use with earthquake recordings. We verify the proposed approach and demonstrate its application using data from two test structures supported on shallow foundations that have been used in forced vibration tests and that have recorded earthquakes. The structures were tested with and without braces to modify their stiffness and were deployed at two sites with different soil conditions. We analyze the results to evaluate experimental period lengthening ratios and foundation damping. The results show (1) strong increases in period lengthening and foundation damping with the wave parameter (dimensionless ratio of structure-to-soil stiffness), (2) compatibility between modal properties from forced vibration testing and earthquake excitation, (3) soil nonlinearity increases period lengthening and modifies foundation damping in a manner that can be reasonably captured in predictive models using equivalent-linear soil properties compatible with a proposed shear strain index.〈/p〉〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 116〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 116〈/p〉 〈p〉Author(s): Seokho Jeong, Domniki Asimaki, Jacob Dafni, Joseph Wartman〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Topographic effects, the modification of seismic shaking by irregular topographies compared to flat ground, have been extensively studied. Very few studies, however, have investigated the effects of the stratigraphy and nonlinear response of the underlying geology on topographic amplification. Furthermore, most experimental studies have been performed in the field, where it is often difficult to establish an ideal flat-ground reference station, as well as to characterize the soil properties and their spatial variability in sufficient detail. Dafni [1] recently tested the seismic response of step-like slopes in a series of centrifuge experiments, where the incident motion, reference station and material properties were characterized in detail. In this study, we investigated the influence of the container boundary on topographic effects observed in the centrifuge experiments by performing numerical simulations with and without the container boundary. Our analysis suggested that the rigid-body rocking motion of the centrifuge container likely increased the experimental topographic spectral ratios, contributing to the discrepancy between the simulated and observed spectral ratios. We also found that although the laminar box lateral boundaries caused spurious reflections, they didn't qualitatively affect the ground surface amplification pattern compared to numerical predictions of the same configuration without boundaries. At the same time, and most importantly, however, we found that the baseplate –by trapping waves scattered and diffracted by the slope– amplified the ground motion at the crest up to one order of magnitude compared to numerical predictions of the response in absence of the baseplate. Our results show that topographic effects can be significantly affected by the underlying soil stratigraphy, and allude to the potentially significant role of this phenomenon in elevating seismic risk in regions with strong topographic relief. The findings of this study also suggest that future studies will benefit from clear understanding and careful considerations of capabilities and limitations of different investigation methods and that the numerical modeling and the lab testing (or the field testing) methods should complement each other.〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 117〈/p〉 〈p〉Author(s): Dan Huang, Shuo Cui, Xiaoqing Li〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Using drilling and blasting method to construct the Mountain tunnel, it is important to monitoring and analysis of blasting seismic wave. The research of simple characteristics of blasting vibration wave such as amplitude, frequency, duration in the previous study, it is lack the detailed characteristics of blasting seismic waves such as frequency distribution characteristics of blasting seismic wave, blasting energy distribution. Thus, Fourier transform and wavelet packet transform are both used to analysis the time - frequency characteristics of measured vibration signal, and the characteristics of its multi-frequency band and energy distribution are discussed. The blasting vibration with the blasting charge of 79.2 kg are did, and the wave are received distance blast source 10 m, 25 m, 40 m. The maximum three vector resultant velocity at 10 m is 5.84 cm/s, which meets the specification safety requirement. Analysis of blasting vibration signals of vertical axis which distance blast source 10 m, the main frequency of this signal is 101.9 Hz, and the relative amplitude is 2382 use by Fourier transform. The Wavelet packet analysis show that, blasting vibration signal has obvious energy distribution characteristics of multi-frequency band. The dominant frequency band (31.25 Hz~125.00 Hz) contains more than 70% of the energy of vibration signal.〈/p〉〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 116〈/p〉 〈p〉Author(s): Nathalie Glinsky, Etienne Bertrand, Julie Régnier〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A two-year seismological experiment in Rognes (South Eastern France) confirms the site effects responsible for the severe damage experienced during the 1909 Provence earthquake. Many experimental and numerical studies have been dedicated to quantify and understand the effect of topography on seismic ground motion. However, these local amplifications depend on many parameters and their causes are not yet fully known. Numerical simulation is an interesting tool to try to explain these phenomena and simplified models are helpful for parametric analysis. For this, we use a discontinuous Galerkin finite element method to study the amplification along 2D profiles. First, an extensive numerical study considering an idealized hill topography investigates the combined effects of the steepness, heterogeneity and the angle of incidence on the surface response and focuses in particular on strong amplifications recorded in gentle slope configurations. Secondly, simulations are applied to a realistic 2D profile of the Rognes area. The confrontation of these numerical results with data from a seismological survey help to confirm the influence of both the topography and in-depth geology.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): P. Dakoulas, P. Vazouras, P. Kallioglou, G. Gazetas〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The seismic performance of an existing gravity quay wall consisting of concrete blocks is investigated using effective stress analysis. The study focuses on the effect of the uncertainty associated with the spatial variability of the material properties in the foundation and backfill zones on the horizontal displacements, settlements and rotations of the wall as well as of porewater pressure behind the wall. A modification of the comprehensive generalized plasticity Pastor-Zienkiewicz constitutive model is used for modelling the cyclic behavior of the sandy gravel and rockfill. Four different numerical models are considered in an extensive parametric study consisting of 180 analyses. The results show that, for constant average relative density, the effects of its spatial variability are smaller than the effects of the frequency characteristics of the earthquake excitation. Moreover, it is shown that a foundation of high relative density may decrease significantly settlements and rotation of the wall, but some reduced horizontal displacements caused partly by block-to-block sliding may still take place. Excess porewater pressures immediately behind the wall are mostly negative, increasing the soil resistance.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Luis E. Yamin, Juan C. Reyes, Rodrigo Rueda, Esteban Prada, Raul Rincon, Carolina Herrera, Julian Daza, Andrea C. Riaño〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The seismic design of buildings and infrastructure components requires the estimation of the hazard considering the dynamic response of the soil deposits, which substantially modifies the characteristics of the input motion at the rock basement. Seismic microzonation studies attempt to identify geologic zones of an area of interest with similar seismic hazard at a local scale. This paper presents a methodology to obtain seismic spectral amplification factors within each soil zone characterization considering the main sources of uncertainty. Results are presented in terms of spectral amplification factors for various seismic intensities and soil profile vibration periods. Design soil amplification factors can then be mapped using the measured vibration period of the soil profile at each location and the seismic intensity at bedrock for a given design return period. Response and design spectra may then be estimated at surface level for every location. Results can be easily integrated into probabilistic risk assessment platforms such as CAPRA (〈a href="http://www.ecapra.org/" target="_blank"〉www.ecapra.org〈/a〉) for hazard and risk evaluations.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): A. Johari, H. Golkarfard〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The soil profile fundamental period is an essential parameter for estimation of site effects on ground motions. However, in most sites, the water table is at a considerable depth and the fundamental period of the unsaturated soil has to be obtained through geotechnical procedures. On the other hand, this parameter is strongly influenced by the uncertainty associated with the site soil properties. In this paper, to assess the influences of non-homogeneity of sites with unsaturated soil, a reliability analysis of fundamental period is presented. For this purpose, a model for predicting unsaturated shear wave velocity using extracted data from six boreholes in three real sites throughout the city of Shiraz in Iran is developed. For the sake of modelling, the soil suction at each depth is calculated from the Soil Water Retention Curve (SWRC) based on the Grain Size Distribution (GSD) of the soil sample. In order for reliability analysis of the sites, constituent variables of the developed model are considered as uncertain and the reliability indices of the fundamental period of the sites boreholes are determined through the Monte Carlo Simulation (MCS) method. The representative reliability indices are combined using the Sequential Compounding Method (SCM) considering the boreholes as parallel components of the system, and the most reliable site is eventually determined.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Wentao Dai, Fabian Rojas, Chen Shi, Yong Tan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, the effect of soil structure interaction and base isolation on the dynamic characteristics of an instrumented bridge is examined using transfer functions and measured motions in the frequency domain. A three dimensional structural model in the frequency domain which accounts for continuous mass distribution along each member and the effect of axial forces as well as rotary inertia is adopted. The dynamic stiffness of pile foundations and surface mat foundation underneath piers, determined separately using appropriate numerical methods, is incorporated into the structural model and the global stiffness matrix. Results are obtained for models of a bridge both without and with isolation pads for various values of the equivalent shear stiffness. This allows one comparing the values of the predominant frequencies and the dynamic amplification of the motions over the frequency range of interests. The transfer functions are also obtained at the bottom of the piers to evaluate the impact and importance of soil structure interaction effect on the dynamic behavior of the system. Results are then compared to the power spectra of the motions recorded at various points of an instrumented bridge (the base, the top of the pier, and the same location on the deck) from an actual earthquake. The method and results can explain many of the observed behavior very well although there are still some points that cannot be resolved due to lack of accurate input information and limitation of the method.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Ross W. Boulanger, Mohammad Khosravi, Ali Khosravi, Daniel W. Wilson〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Numerical simulations of a centrifuge model test of an embankment on a liquefiable foundation layer treated with soil-cement walls are presented. The centrifuge model was tested on a 9-m radius centrifuge and corresponded to a 28 m tall embankment underlain by a 9 m thick saturated loose sand layer. Soil-cement walls were constructed through the loose sand layer over a 30 m long section near the toe of the embankment and covered with a 7.5 m tall berm. The model was shaken with a scaled earthquake motion having peak horizontal base accelerations of 0.05 g, 0.26 g, and 0.54 g in the first, second, and third events, respectively. The latter two shaking events caused liquefaction in the loose sand layer. Crack detectors embedded in the soil-cement walls showed that they developed only minor cracks in the second shaking event, but sheared through their full length in the last shaking event. The results of the centrifuge model test and two-dimensional nonlinear dynamic simulations are compared for the two stronger shaking events using procedures common in engineering practice. The effects of various input parameters and approximations on simulation results are examined. Capabilities and limitations in the two-dimensional simulations of soil-cement wall reinforcement systems, with both liquefaction and soil-cement cracking effects, are discussed. Implications for practice are discussed.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Ioanna-Kleoniki Fontara, Winfried Schepers, Stavros Savidis, Frank Rackwitz〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉An alternative approach to local transmitting boundaries for wave propagation problems in unbounded media is the application of the Perfectly Matched Layers (PML) around the finite region of interest. The PML model consists of absorbing layers that absorb almost perfectly propagating waves of all non-tangential angels-of-incident and all non-zero frequencies. This paper presents and verifies the concept of FE/PML methodology on the basis of two different formulations for the PML model in the context of time harmonic wave propagation analysis. A finite element numerical scheme is developed in which both PML formulations are successfully implemented as a macro-finite element in a commercial FEM program. Moreover, the parameters that influence the performance of the FE/PML method are extensively discussed and recommendations are given for the proper selection. Classical soil-structure interaction problems of surface or embedded rigid footing on homogeneous or heterogeneous half-plane containing layers and tunnels are investigated and the high accuracy and the easy implementation of FE/PML computational tool is demonstrated.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): Hamed Hamidi, Horr Khosravi, Reza Soleimani〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The article aims to 〈strong〉a.〈/strong〉 introduce a technique to generate long-period waveforms having fling-step effect at near fault and 〈strong〉b.〈/strong〉 study the effect of fling-step on the structural performance of buildings. The study focuses on the fling-step effect which is related to large co-seismic displacement. For this purpose, seismological parameters of Kocaeli 1999 earthquake have been computed through an evolutionary multi objective approach (MO-GA) and Theoretical-based Green's Function (TGF) method with regard to specific objectives such as permanent displacement, response spectra, and multi-taper spectra. Thereafter many accelerograms were generated at desired near stations and the fling-step effects were removed from the accelerograms by a specific technique. Subsequently, three3-, 9- and 20-story steel frames were modeled in Opensees and the structural responses were obtained using nonlinear time history analyses. Findings from this study demonstrate that fling-step would affect the seismic demand fairly high when the ratio of the fundamental period of the structure to fling rise time (pulse duration) varies from 0.5 to 1.1. Also a good agreement between the responses of the structures subjected to generated ground motions and as-recorded ground motions was observed when this ratio equals 0.5. In most cases, an increase in seismic demand was observed in the absence of fling-step pulse.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): Jonathan F. Hubler, Adda Athanasopoulos-Zekkos, Dimitrios Zekkos〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Understanding the factors that affect the monotonic and cyclic response of gravelly soils during earthquake events is critical to infrastructure design. In this study a large-size Cyclic Simple Shear (CSS) device was utilized to perform monotonic and cyclic shear tests on mixtures of either subrounded 9 mm Pea Gravel or angular 8 mm Crushed Limestone (CLS8) with subrounded Ottawa C109 sand. Tests were performed in constant volume conditions and shear wave velocity was measured for each specimen. Monotonic and cyclic test results at D〈sub〉r〈/sub〉 = 47% show that there is an optimum mixture percentage that results in the greatest shear strength and resistance to liquefaction (40% Sand for Pea Gravel Mixtures and 60% Sand for CLS8 Mixtures). The effects of particle angularity, cyclic stress ratio, and initial vertical stress on monotonic and cyclic response of loose and dense gravel mixtures were investigated and are presented. Comparison of the results from the cyclic simple shear tests with existing liquefaction triggering charts suggests the need for improved charts for gravelly soil liquefaction evaluation.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 5 September 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering〈/p〉 〈p〉Author(s): Emmanuel E. Gdoutos〈/p〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Hadi Farahi Jahromi, Fardin Jafarzadeh, Masood Samadian Zakaria〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉This paper studies the influence of burial depth on slope response and pipe performance under earthquake induced landslide. Three physical models are constructed and tested using 1 g shaking table device. The slope is divided into four sections as toe, lower and upper sections of the slope face and crest. The pips which perpendicularly cross the slope are embedded at these positions in three burial depths to demonstrate burial depth effect in each section.〈/p〉 〈p〉According to the experiments, dynamic slope response which moderately develops at deeper depths at toe and lower section, displays a clear downtrend at upper section and crest. Also, the pipe response depends on pipe route and slope displacement pattern. The pipe deformations have positive correlation with depth at upper section and crest, but show opposite behavior at toe and lower section. Moreover, the horizontal strains impact on total strains in buried pipes reduces at greater depths.〈/p〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): Biao Wei, Chengjun Zuo, Xuhui He, Lizhong Jiang, Teng Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A continuous bridge in high-speed railway is close to several known faults in China. Those faults, respectively at different distances from the bridge site, will produce different ground motions with the different ratios of vertical component to the horizontal component at the bridge site. It is necessary to identify the influence of vertical ground motions on the seismic responses and vulnerabilities of the track-bridge system. This paper solved this problem by carrying out an incremental dynamic analysis (IDA) and a further seismic fragility analysis on a widely used continuous bridge in China. The results show that the damage probabilities of most bridge and track components increase along with the increase of vertical part in ground motions. This trend is significant for the sliding layer of track part in the longitudinal direction and the piers of bridge part in any direction, however, insignificant for the bearings of bridge part in any direction. Moreover, this trend is more significant for the track part across the girder gap due to the different seismic responses of adjacent bridges. The seismic design of track-bridge system should rigorously take the vertical part of ground motions into account.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Niki D. Beskou, George A. Papagiannopoulos, Athanasios P. Chassiakos〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The dynamic response of rigid walls retaining a cross-anisotropic poroelastic soil layer over bedrock to seismic horizontal excitation is determined analytically under conditions of plane strain. The problem is treated as a special case of that of a pair of rigid walls with a large separation distance. Use is made of Biot’s anisotropic poroelastodynamic theory. Assuming time harmonic excitation, one is able to achieve an exact u-p formulation of the problem in the frequency domain. Expansion of the displacements and the pore-water pressure in terms of Fourier sine and cosine series along the horizontal direction, reduces the partial differential equations of motion in the frequency domain into a system of three ordinary differential equations, which can be easily solved analytically. Thus, closed form expressions for the seismic soil pressure, the distance from the base of the point of application of the resultant seismic pressure and the base shear force and bending moment are obtained. From the above cross-anisotropic poroelastic solution its special cases of isotropic poroelastic solution and cross-anisotropic elastic solution are obtained and compared with the corresponding existing analytical solutions for validation purposes. Finally, parametric studies are performed in order to assess the effect of cross-anisotropy on the seismic response of the wall-soil system.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Shilpa Thakur, K.A. Abhinav, Nilanjan Saha〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This work attempts to investigate the load mitigation effects on foundations of NREL 5-MW offshore wind turbine (OWT) supported on fixed structures using blade trailing edge flaps. The analysis is subjected to turbulent wind and irregular wave loads. The offshore wind turbine is simulated for five met-ocean conditions for Indian scenario, covering operational to the parked region of turbine. Sea states being stochastic, the responses are obtained using average of Monte Carlo simulations. The blade element momentum theory is used to obtain the aerodynamic loads by modelling in a multi-body framework while the hydrodynamic and geotechnical analysis are performed in a finite element framework. Soil-structure interaction is modelled using nonlinear Winkler spring model along the length of the pile. The trailing edge flaps are numerically implemented through a dynamic link library into the aerodynamic program. Loose sandy soils with uniform density is considered for analysis. The results bring out the importance of including blade trailing edge flaps in OWT studies with significant response reduction (2.1–16.0%) for designing pile foundations.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Ebrahim Afsar Dizaj, Rahmat Madandoust, Mohammad M. Kashani〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A probabilistic framework for seismic vulnerability analysis of corroded Reinforced Concrete (RC) frame structures is developed. An advanced nonlinear finite element modelling technique is used to accurately simulate the nonlinear behaviour of prototype corroded RC frames over their service life. Different sources of uncertainties including modelling uncertainties, geometrical uncertainties and spatial variability of pitting corrosion are considered through Monte Carlo simulation and using Latin Hypercube Sampling (LHS) technique. A set of new seismic damage limit states (SDLS) are defined accounting for multiple failure modes of the corrosion damaged frames by means of pushover analyses. The influence of corrosion on nonlinear dynamic behaviour of corroded RC frames is investigated through Incremental Dynamic Analysis (IDA) of proposed frame structures under 44 far-field ground motions. The impact of considering corrosion damaged SDLS, spatial variability of pitting corrosion, and record-to-record variability on seismic vulnerability of RC frames are explored and discussed in detail. It is concluded that disregarding the influence of corrosion on SDLS significantly underestimates the probability of failure of corroded RC frames. The analyses results show that spatial variability of pitting corrosion does not have a significant impact on global nonlinear behaviour and seismic vulnerability/reliability of corroded RC frames.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): R. Sharbati, F. Khoshnoudian, H.R. Ramazi, H.R. Amindavar〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The aim of this research is to develop a stochastic model for generating synthetic ground motions in accordance with a recorded ground motion. In this model, Complex discrete wavelet transform is used to extract wavelet coefficients of a ground motion, and the Gaussian mixture distribution to capture the statistical behavior and simulate these coefficients. Synthetic ground motion is generated by applying inverse wavelet transform to synthetic wavelet coefficients that are extracted based on the fitted Gaussian mixture models and a random sign generator. This model is able to generate an ensemble of synthetic ground motions with temporal and spectral nonstationary characteristics similar to those of the recorded ground motion. In contrast to the previous models, the Gaussian mixture model is able to simulate several dominant frequency peaks at each time, multiple peaks in the temporal amplitude of ground motions, and near-fault ground motions containing several pulses. Also, the Gaussian mixture model provides good estimates of the energy distribution and the inelastic response spectrum of recorded ground motions. Besides these capabilities, the proposed model demands much less computational effort than the previous models.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉In this paper, we propose a stochastic-parametric model for simulation of ground motions. This model simulates the near-fault ground motions containing any number of pulses, the ground motions that have multiple peaks in their temporal amplitude, the ground motions that have several dominant frequency peaks at each time, and the mainshock-aftershock ground motion sequences, while the previous models cannot do it.〈/p〉 〈p〉The block diagram of the proposed model is shown in following figure. It is divided into three parts: the first part refers to modeling of the target ground motion using the complex discrete wavelet transform (CDWT) and the Gaussian mixture (GM) distribution; the second part refers to the generation of synthetic ground motion using the fitted GM distributions; and the third part refers to the comparison of synthetic and real ground motions to validate the proposed model.〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0267726117306796-fx1.jpg" width="466" alt="fx1" title="fx1"〉〈/figure〉〈/p〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Wuchuan Pu, Ming Wu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Building structures constructed of timber components are characterized by a pinching-type hysteresis that indicates degraded stiffness and strength. Owing to the significant effect of their loading history, these types of structures may be more prone to failure when subjected to sequential seismic excitations. This study investigates the effect of seismic ground motion sequences on the ductility demands and residual displacements of building structures with pinching hysteretic models. A single-degree-of-freedom (SDOF) structure is considered, and is modeled with the hysteretic model consisting of a slip element and a bilinear element. The seismic ground motion sequences are simulated by repeating ground motion records with differing intensities. Through dynamic time history analysis, the effect of the seismic intensity, ductility level, hysteretic parameters, and site conditions are investigated. The results indicate that the seismic sequences amplify the ductility demands of pinching hysteretic structures, and this effect is more significant for short period structures. The pinching hysteretic structures have ductility amplification factors that are higher than those of bilinear hysteretic structures. The residual displacement shows a relatively strong correlation to the maximum displacement, and the ratio of residual displacement to maximum displacement approximately obeys an exponential probability distribution. Based on the numerical results, empirical formulas for estimating the ductility demand amplification and the probability density distribution of the residual displacement are proposed.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Priyamvada Singh, Sushil Kumar, Pitam Singh〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The attenuation of seismic wave is one of the basic physical parameters which is closely related to the seismicity and regional tectonics activity of a particular area. This is also important for seismic hazard measurement. Seismic wave attenuation for local earthquakes is determined from the analysis of direct body waves and coda waves. The dimensionless parameter, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0036.gif" overflow="scroll"〉〈mrow〉〈mi mathvariant="italic"〉Q〈/mi〉〈/mrow〉〈/math〉, is studied in the present work, which is defined as a measure of the rate of decay of the coda waves or body waves within a specific frequency band. Digital seismogram data of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0037.gif" overflow="scroll"〉〈mrow〉〈mn〉75〈/mn〉〈/mrow〉〈/math〉 earthquakes that occurred in Garhwal Himalaya region during 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0038.gif" overflow="scroll"〉〈mrow〉〈mn〉2004〈/mn〉〈/mrow〉〈/math〉–〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0039.gif" overflow="scroll"〉〈mrow〉〈mn〉2006〈/mn〉〈/mrow〉〈/math〉 and recorded at 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0040.gif" overflow="scroll"〉〈mrow〉〈mn〉20〈/mn〉〈/mrow〉〈/math〉 different stations have been analyzed to study the seismic body and coda wave attenuation. Seismic body wave attenuation characteristics are examined by estimating the frequency dependent relationship of quality factors for 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0041.gif" overflow="scroll"〉〈mrow〉〈mi〉P〈/mi〉〈/mrow〉〈/math〉-waves, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0042.gif" overflow="scroll"〉〈msub〉〈mrow〉〈mi〉Q〈/mi〉〈/mrow〉〈mrow〉〈mi〉α〈/mi〉〈/mrow〉〈/msub〉〈/math〉 and for 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0043.gif" overflow="scroll"〉〈mrow〉〈mi〉S〈/mi〉〈/mrow〉〈/math〉-waves, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0044.gif" overflow="scroll"〉〈msub〉〈mrow〉〈mi〉Q〈/mi〉〈/mrow〉〈mrow〉〈mi〉β〈/mi〉〈/mrow〉〈/msub〉〈/math〉 in the frequency range 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0045.gif" overflow="scroll"〉〈mrow〉〈mn〉1.5〈/mn〉〈/mrow〉〈/math〉–〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0046.gif" overflow="scroll"〉〈mrow〉〈mn〉28〈/mn〉〈/mrow〉〈/math〉 Hz, using 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0047.gif" overflow="scroll"〉〈mrow〉〈mn〉95〈/mn〉〈/mrow〉〈/math〉 seismic observations with hypo central distance less than 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0048.gif" overflow="scroll"〉〈mrow〉〈mn〉100〈/mn〉〈/mrow〉〈/math〉 km. The extended coda normalization method was applied. The average value of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0049.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mi〉Q〈/mi〉〈/mrow〉〈mrow〉〈mi〉α〈/mi〉〈/mrow〉〈/msub〉〈mrow〉〈/mrow〉〈/mrow〉〈/math〉 is found to be varied from 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0050.gif" overflow="scroll"〉〈mrow〉〈mn〉45.10〈/mn〉〈/mrow〉〈/math〉 at 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0051.gif" overflow="scroll"〉〈mrow〉〈mn〉1.5〈/mn〉〈/mrow〉〈/math〉 Hz to 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0052.gif" overflow="scroll"〉〈mrow〉〈mn〉1400.0〈/mn〉〈/mrow〉〈/math〉 at 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0053.gif" overflow="scroll"〉〈mrow〉〈mn〉28〈/mn〉〈/mrow〉〈/math〉 Hz, while it varies from 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0054.gif" overflow="scroll"〉〈mrow〉〈mn〉109.02〈/mn〉〈/mrow〉〈/math〉 at 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0055.gif" overflow="scroll"〉〈mrow〉〈mn〉1.5〈/mn〉〈/mrow〉〈/math〉 Hz to 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0056.gif" overflow="scroll"〉〈mrow〉〈mn〉3987.0〈/mn〉〈/mrow〉〈/math〉 at 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0057.gif" overflow="scroll"〉〈mrow〉〈mn〉28〈/mn〉〈/mrow〉〈/math〉 Hz for 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0058.gif" overflow="scroll"〉〈msub〉〈mrow〉〈mi mathvariant="italic"〉Q〈/mi〉〈/mrow〉〈mrow〉〈mi〉s〈/mi〉〈/mrow〉〈/msub〉〈/math〉. The estimated frequency dependent relation for quality factors are 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0059.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mi〉Q〈/mi〉〈/mrow〉〈mrow〉〈mi〉α〈/mi〉〈/mrow〉〈/msub〉〈mo〉=〈/mo〉〈mrow〉〈mo stretchy="false"〉(〈/mo〉〈mn〉29.077〈/mn〉〈mo〉±〈/mo〉〈mn〉8.5〈/mn〉〈mo stretchy="false"〉)〈/mo〉〈/mrow〉〈msup〉〈mrow〉〈mi〉f〈/mi〉〈/mrow〉〈mrow〉〈mo stretchy="false"〉(〈/mo〉〈mn〉1.16〈/mn〉〈mo〉±〈/mo〉〈mn〉0.01〈/mn〉〈mo stretchy="false"〉)〈/mo〉〈/mrow〉〈/msup〉〈mrow〉〈/mrow〉〈/mrow〉〈/math〉 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0060.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="italic"〉Q〈/mi〉〈/mrow〉〈mrow〉〈mi〉β〈/mi〉〈/mrow〉〈/msub〉〈mo〉=〈/mo〉〈mrow〉〈mo stretchy="false"〉(〈/mo〉〈mn〉67.84〈/mn〉〈mo〉±〈/mo〉〈mn〉13.5〈/mn〉〈mo stretchy="false"〉)〈/mo〉〈/mrow〉〈msup〉〈mrow〉〈mi〉f〈/mi〉〈/mrow〉〈mrow〉〈mo stretchy="false"〉(〈/mo〉〈mn〉1.18〈/mn〉〈mo〉±〈/mo〉〈mn〉0.02〈/mn〉〈mo stretchy="false"〉)〈/mo〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉 for 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0061.gif" overflow="scroll"〉〈mrow〉〈mi〉P〈/mi〉〈/mrow〉〈/math〉 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0062.gif" overflow="scroll"〉〈mrow〉〈mi〉S〈/mi〉〈/mrow〉〈/math〉-waves, respectively. The rate of increase of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0063.gif" overflow="scroll"〉〈mrow〉〈mi mathvariant="italic"〉Q〈/mi〉〈mo stretchy="false"〉(〈/mo〉〈mi〉f〈/mi〉〈mo stretchy="false"〉)〈/mo〉〈/mrow〉〈/math〉 for 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0064.gif" overflow="scroll"〉〈mrow〉〈mi〉P〈/mi〉〈/mrow〉〈/math〉 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0065.gif" overflow="scroll"〉〈mrow〉〈mi〉S〈/mi〉〈/mrow〉〈/math〉 waves in this region is comparable with the other regions of the Himalayas. The ratio 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0066.gif" overflow="scroll"〉〈mrow〉〈mfrac〉〈mrow〉〈msub〉〈mrow〉〈mi〉Q〈/mi〉〈/mrow〉〈mrow〉〈mi〉β〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈mrow〉〈msub〉〈mrow〉〈mi〉Q〈/mi〉〈/mrow〉〈mrow〉〈mi〉α〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/mfrac〉〈mrow〉〈/mrow〉〈/mrow〉〈/math〉 is greater than unity in the entire analyzed frequency range. It indicates that scattering is an important factor contributing to the attenuation of body wave in the region. The low 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0067.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mi〉Q〈/mi〉〈/mrow〉〈mrow〉〈mi〉α〈/mi〉〈mo〉,〈/mo〉〈mi〉β〈/mi〉〈/mrow〉〈/msub〉〈mrow〉〈/mrow〉〈/mrow〉〈/math〉 values or high, attenuation at lower frequencies and high 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0068.gif" overflow="scroll"〉〈msub〉〈mrow〉〈mi〉Q〈/mi〉〈/mrow〉〈mrow〉〈mi〉α〈/mi〉〈mo〉,〈/mo〉〈mi〉β〈/mi〉〈/mrow〉〈/msub〉〈/math〉 values or low attenuation at higher frequency may indicate that the heterogeneity decreases with increasing depth in the study region.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): Duofa Ji, Weiping Wen, Changhai Zhai, Evangelos I. Katsanos〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉120 earthquake ground motions recorded on soft soil sites were employed to assess, through response history analysis of simplified systems, the residual displacement demand, 〈em〉C〈/em〉〈sub〉〈em〉r〈/em〉〈/sub〉, defined as the ratio of the residual displacement to the maximum elastic displacement. Single degree of freedom systems were considered and the lateral strength ratio was parametrized to account for varying structural inelasticity. Four hysteretic laws were chosen to represent degrading and non-degrading performance while variation in the post-yield stiffness was considered. The analysis scheme enabled assessing the relationship of the residual displacement with the aforementioned structural characteristics. The residual displacement demand was found to be sensitive in the post-yield stiffness ratio. An equation was finally introduced to accommodate the reliable estimation of residual displacement ratio, the latter being beneficial for evaluating the seismic performance of existing structures built on soft soil sites.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Lindung Zalbuin Mase, Suched Likitlersuang, Tetsuo Tobita〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper presents a site-specific analysis of ground response during the Tarlay Earthquake on March 24, 2011 in Northern Thailand. In this study, the NGA (Next Generation Attenuation) models were selected to predict ground motions due to the earthquake event. The equivalent linear and non-linear approaches were employed in the one-dimensional ground response analysis. Furthermore, the spectral responses produced by the equivalent linear and non-linear approaches were compared with the seismic design code of Thailand. The results showed that the ground motion from the NGA models agree with the strong motion parameters of Tarlay Earthquake. Peak ground acceleration (PGA) at ground surface obtained from both equivalent linear and non-linear approaches certainly results in the high amplification factor. In general, the study results could bring an attention to the local engineer to consider the seismic design value for Northern Thailand, particularly if the stronger earthquake happens in the future.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): Mustafa Erdik, Ömer Ülker, Bahadır Şadan, Cüneyt Tüzün〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉There is a special need to preserve the functionality of critical structures, such as hospitals, under severe earthquakes. In this sense, seismic isolation technology serves as a vital design method for the protection of their functionality.〈/p〉 〈p〉In Turkey, seismic isolation technology has been applied at an accelerated pace to new or retrofitted buildings and infrastructures for earthquake protection essentially after the 1999 Kocaeli Mw7.4 Earthquake. Several guidelines and a new official code are prepared to encourage and regulate the on-going applications.〈/p〉 〈p〉To enable the post-earthquake functionality of hospitals, the Ministry of Health public private partnership program foresees to build health campuses with seismic isolation. As of 2017, 21 health projects are complete or under construction with total investment of more than USD 23 billion.〈/p〉 〈p〉Following a general review of seismic isolation design, the essential features of the recent seismic isolation code are provided and compared with European, Japanese and US Codes.〈/p〉 〈p〉After a brief survey of base isolated hospitals in the world, two examples of large scale hospitals with seismic isolation are provided.〈/p〉 〈p〉The Basibüyük Training and Research Hospital in Istanbul, retrofitted with seismic isolation, encompasses 750 beds in 113.000 m〈sup〉2〈/sup〉 floor area and is the largest hospital in the world retrofitted with a seismic isolation system consisting of 688 lead rubber and 154 sliding bearings.〈/p〉 〈p〉The newly built Adana Integrated Health Campus (City Hospital) has 430,000 m〈sup〉2〈/sup〉 floor area and houses 1500 beds. With an isolation system composed of 1552 triple curved surface friction sliders, the hospital is currently the largest base isolated hospital in the world.〈/p〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Giovanni Ferrante Cavallaro, Antonella Bianca Francavilla, Massimo Latour, Vincenzo Piluso, Gianvittorio Rizzano〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The experimental activity presented in this work intends to study in detail the cyclic behaviour of a set of three different friction shims preliminary selected in a previous experimental work regarding the behaviour of friction dampers of Sliding Hinge Joints (SHJs). These connections are able to dissipate seismic energy by means of friction through a proper application of capacity design principles. Their bending resistance is proportional to the slip resistance of a friction device which is usually installed at the bottom beam flange and can be governed controlling only two parameters: the friction coefficient and the clamping force of the high strength bolts.〈/p〉 〈p〉The main goal of the experimental campaign presented is to investigate the dependence of the friction coefficient on some of possible significant parameters. In particular, the 51 tests presented are devoted to evaluate the response of the interfaces taking into account the effect of the bolts preloading, the effect of the type of washers and the influence of the random material variability. In detail, the tests have been carried out with four different configurations of washers (with flat washers and disk springs), considering a possible range of values of the clamping forces (between 40% and 100% of the standard proof preload). The results of the experimental activity are reported in the paper proposing a possible definition of the values of the friction coefficients to be used in design and regression analyses of the experimental data of the slip tests to be used in simplified rigid-plastic modelling for seismic analyses.〈/p〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Xiaoqiong Li, Zhong-Xian Li, Adam J. Crewe〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Many very large bridges with high piers and long spans are under rapid construction in mountainous regions especially in Western China. However, the current seismic design methods in China are based on a code which only applies to bridges with span up to 150 m. To evaluate the risk of the inapplicable design method and the influence of spatially variable ground motions (SVGM) on the seismic response of very large bridges, a high-pier, long-span, continuous RC frame bridge is numerically studied. This study considers whether multiple support excitation can be simplified into specific uniform excitation cases while guaranteeing the conservative seismic demands for this bridge. Non-stationary SVGM on both bedrock and the surface of multiple soil layers are simulated including wave passage effects, coherency effects and site amplification effects. The nonlinear dynamic finite element model of the bridge is analysed for two groups of earthquake motions, namely group 1 - bedrock and group 2 - ground surface excitations. Each group contains three different excitations, i.e. i) multiple support excitation ii) the largest and iii) the smallest accelerations from the SVGM. The relative displacements, internal force responses and ultimate damage modes are obtained and compared. For this bridge the uniform ground motion input with the largest accelerations provides conservative seismic demands for most structural components when the site amplification effect is not considered (group 1). However, for the ground surface motions, where site amplification needs to be taken into account (group 2), in several cases the uniform ground motion with the largest accelerations results in lower response than that predicted when considering SVGM. The present results indicate that only when the bridges are located on ideal simple topography where site effects have little influence, the uniform excitation with the largest accelerations taken from the SVGM may be an alternative input for seismic analysis. However, for bridges on complex terrain, where site effects can significantly amplify the ground motions at the bedrock, SVGM need to be applied as input for the seismic analysis. As spatial variability of input motion is not a mandatory requirement in the Chinese bridges design code, these results suggest that the existing design code for very large bridges should be modified accordingly.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Vincent Brière, Veronica Santos, Colin A. Rogers〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉An innovative configuration for cold-formed steel (CFS) framed and sheathed shear walls developed to address the need for a ductile lateral framing system of high shear resistance appropriate for mid-rise buildings is presented in this paper. This shear wall configuration comprises a sheathing placed at the mid-line of the framing, and hence is known as either a centre-sheathed or mid-ply wall. A laboratory based research program was conducted following an iterative design, analysis and testing process. The testing included fifteen 1218 mm × 2438 mm shear walls subjected to in-plane displacement-based monotonic and cyclic loading. The test specimens were able to reach shear resistances substantially exceeding the capacity of the CFS walls listed in the AISI S400 Standard, while attaining storey drift values superior to 6% in the best case. A preliminary equation-based nominal shear strength prediction method has been developed, reflecting the shear wall's innovative configuration and superior behaviour.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): T.G. Sitharam, Resmi Sebastian, Febin Fazil〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The vibration isolation of buildings housed with sensitive equipment is always a challenging one due to the stringent vibration criteria imposed on them. The paper presents a case study on the vibration isolation scheme adopted for an important building of space research agency. The vibration levels in the building had to follow the vibration criterion which is in the form of a set of one – third octave band velocity spectra, expressed as vibration criterion curves. Various sources that can generate vibrations in the building were identified and assessed. The external sources and the internal sources of vibration were analyzed and the possible limits of vibrations were evaluated. The selection procedure of design frequency, which is the significant step in the design of vibration isolation trench under the passive isolation scheme, is explained. Numerical simulations were developed to evaluate the influence of trench parameters on the amplitude reduction of Rayleigh waves propagating across the trench. Based on the results from numerical simulations, the vibration isolation trench was designed to reduce the amplitudes of vibrations produced from external and internal sources.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Jonathan Salvi, Fabio Pioldi, Egidio Rizzi〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Tuned Mass Damper (TMD) devices are widely adopted as a valid mechanical solution for the vibration mitigation of structural systems and buildings under dynamic excitation. In the specific challenging context of seismic engineering, TMDs may represent a convenient option for both aseismic structural design and seismic retrofitting. However, the expectable efficiency rate of TMDs in that context is still debated. Besides, potential Soil-Structure Interaction (SSI) effects may become crucial in the mechanical system, and should properly be taken into account for the optimum TMD design, in order to avoid possible de-tuning. This work contributes to this framework, by investigating the effectiveness of an optimum TMD in reducing the linear structural response to strong-motion earthquakes of a given set of Multi-Degree-Of-Freedom (MDOF) low- and high-rise shear-type frame structures, by embedding SSI within the dynamic and TMD optimisation model. The TMD is seismically tuned through a dedicated two-variable optimisation procedure, for each specific case (primary structure, seismic event and soil type), therefore providing the optimum device setting for each given context. Average primary structure response indices are specifically targeted to that purpose, while maximum ones are monitored. A quite considerable range of optimisation cases is considered (eighty instances), to outline rather general considerations and average trends on TMD optimisation and effectiveness within the seismic SSI framework, for both low- and high-rise buildings. Such an investigation shall provide useful guidelines for a comprehensive tuning of TMDs in mechanical systems and specifically in the presence of seismic SSI, to be consulted in view of real-case applications.〈/p〉〈/div〉 〈div〉 〈h6〉Graphical abstract〈/h6〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0267726118300861-fx1.jpg" width="420" alt="fx1" title="fx1"〉〈/figure〉〈/p〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Kostas Senetakis, Meghdad Payan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Damping ratio is a critical soil property used for the geophysical characterization of sediments and the study of the behavior of geo-materials against wave propagation. Two types of damping ratios are examined and quantified in this study conducting small-strain resonant column tests in torsional and flexural modes of vibration. During the course of this study, a variety of non-plastic soils from clean sands to silt-sand mixtures with variable index properties are examined and the laboratory specimens are subjected to isotropic stress conditions. Measurements and comparisons are conducted between flexural (〈em〉D〈/em〉〈sub〉〈em〉fo〈/em〉〈/sub〉) and torsional (〈em〉D〈/em〉〈sub〉〈em〉so〈/em〉〈/sub〉〈em〉)〈/em〉 damping. For clean sands, based on the data analysis, an empirical equation for (〈em〉D〈/em〉〈sub〉〈em〉fo〈/em〉〈/sub〉) is derived which is given as a function of (〈em〉D〈/em〉〈sub〉〈em〉so〈/em〉〈/sub〉〈em〉)〈/em〉 and the characteristics of the sands. Flexural damping ratios for all the tested materials are observed to have fairly equal or greater values and lower rate of variation with isotropic confining pressure compared to their torsional counterparts (〈em〉D〈/em〉〈sub〉〈em〉so〈/em〉〈/sub〉〈em〉)〈/em〉. Furthermore, the proportions of small-strain flexural and torsional damping ratios (〈em〉D〈/em〉〈sub〉〈em〉fo〈/em〉〈/sub〉〈em〉/D〈/em〉〈sub〉〈em〉so〈/em〉〈/sub〉〈em〉)〈/em〉 are obtained for all the tested sands and silty sands and plotted against the isotropic confining pressure. The results highlight the important role of particle shape, grain size distribution and silt content on the behavior of non-plastic geo-materials in terms of the ratio (〈em〉D〈/em〉〈sub〉〈em〉fo〈/em〉〈/sub〉〈em〉/D〈/em〉〈sub〉〈em〉so〈/em〉〈/sub〉〈em〉)〈/em〉.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Ileana Corbi, Ottavia Corbi, Haitao Li〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The paper falls within the framework of dynamic control of existing structures exhibiting non-linear behaviour. On the basis of some previous research developed by the authors, it specifically focuses on the analytical setup and development of a control algorithm for mitigating in an improved way the response of non-linear spatial structures, made of masonry. The presented setup does not involve the gross simplifications of the structural model behaviour that are usually adopted in these cases; on the contrary it proposes a more appropriate full mathematical formulation, which is, nevertheless, made still manageable for numerical purposes and significantly more reliable than alternative approaches.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): Xu Wang, Jihua Fu, Chengpei Tang, Zhitao Li, Jianjun Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Detection of P waves in the seismic phrases is essential for studying the earthquake ground motion. A P waves’ automatic picking by detecting the changes of seismic signals’ stationary random process is put forward through the similarity analysis in the paper. Firstly a known template of stationary random process is composed or chosen. And the similarity coefficients between the chosen template and the seismic signal are calculated, and they present the stability of the seismic signal. Then a given threshold of the similarity coefficients’ changes is applied to detect the significant changes of the similarity coefficients, which represents the P waves’ arrivals. By the similarity coefficient method, the detecting results of P waves accompanied confidence level are obtained. This similarity analysis method was tested by both the main-shocks and the aftershocks of the M〈sub〉s〈/sub〉 8.0 Wenchuan Earthquake. Comparing the picking results, the similarity coefficient method performed better than the short-term and long-term average ratio (STA/LTA) algorithm. For given examples, the mean error of the P waves’ picking time by the similarity analysis method (−0.13 s) is less than the mean error by the STA/LTA method (−0.33 s). When noise is added, the mean error of the P waves’ picking time by the similarity analysis method increased to 0.25 s, that is still less than the mean error by the STA/LTA method (4.07 s).〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): Masoud Sharifzadeh Asli, Seyed Majdeddin Mir Mohammad Hosseini, Alireza Jahanirad〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Based on recent studies, providing suitable conditions for a soil-structure system to behave non-elastically in response to the forced vibrations resulting from seismic activity is potentially advantageous. High-rise structures with rigid column-base connections often withstand considerable moments which can create plastic hinges at it. The Inclusion of rocking motions in the foundation in structural analysis is a new approach in seismic designs that can reduce the column-base moments and transfer the plastic hinge(s) to the soil. Creating soil slippage on failure surfaces, which in design concept is termed by “rocking isolation”, can act as a “fuse” for protecting the superstructure against damages. Although favorable in terms of limiting the inertial forces applied to the superstructure, rocking motions can cause undesirable foundation settlement in structures with low safety factor against static vertical loads (F.S.v). Since the soil region yielded as a result of rocking motions lies in the shallow depths of the foundation, “shallow soil improvement” can be considered as an option to ensure that F.S.v is sufficiently large and to avoid unpredictable risks regarding residual rotation and increasing settlement. The geogrid and geocell were used as reinforcement elements at different depth ratios. Based on the results, using geocell at depth ratios less than 0.25 would reduce settlements effectively.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): W.D. Liam Finn〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The key elements of performance-based design will be illustrated and discussed in the context of designing cost effective remedial measures for embankment dams with liquefiable materials in the foundation. This situation is considered one of the more challenging areas of performance based design. Some of the key elements that will be considered will be the selection of performance criteria, selection of an appropriately validated analysis program and calibrating the constitutive model to represent material properties in the field. Major elements of performance based seismic design will be explored using typical case histories from practice such as Sardis Dam in Mississippi, Mormon Island Auxiliary Dam in California, and Flood Protection Dikes in Hokkaido, Japan. A primary source of concern about performance based design based on the results of finite element or finite difference methods of analysis is the reliability of the analyses. Reliability is enhanced by due diligence in the selection of a well-validated program and an appropriately calibrated constituted constitutive model. These issues are discussed in the paper, but there remains a residual concern because there is no field response data on large dams by which our real capability can be assessed.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): Erlei Yao, Yu Miao, Suyang Wang, Xiaohong Long〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A new method of deriving evolutionary power spectral density (EPSD) function on surface of a canyon site with multiple soil layers was proposed. After the power spectral density on the base rock was determined, the auto/cross power spectral density function on site surface can be obtained by using the frequency response function (FRF), and a series of ground motions can then be generated. However, the spectral nonstationarity was neglected because the parameters in the FRF varied only with frequency. In the present paper, the time-varying frequency and damping ratio in FRF for each soil layer were incorporated for the derivation of the EPSDs on the surface. The influence of local site conditions on the coherency loss was considered. Spatially variable ground motions (SVGMs) possessing full nonstationarity were then simulated. A set of verifications was conducted, and the results showed that the proposed method is reliable.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 20 September 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering〈/p〉 〈p〉Author(s): Yao Li〈/p〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): Lidong Wang, Zhihui Zhu, Yu Bai, Qi Li, Pedro Alves Costa, Zhiwu Yu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A fast computation method that can be used for efficient analysis of full scale three-dimensional random vibrations induced by railway traffic is presented in this paper. The method uses the pseudo-excitation method (PEM) for random analysis and the proposed multi-point synchronous algorithm (MPSA) for solution of the large sparse linear equations of the train-track-soil coupled system (TTSCS). A mixed two- and three-dimensional TTSCS model is established firstly. Based on the linear Hertzian wheel/rail contact relationship, the time-dependent equations of motion of the TTSCS are deduced. This formulation leads to a global system of equations that can be solved in a directional manner without the need for iterative processes. By means of the PEM, the self-excitation induced by the random track irregularity is transformed into a series of deterministic harmonic excitation vectors. To accelerate the computation, a fast computation strategy is proposed. In the numerical example, the proposed method is validated through comparison with field measured results. Comparison of the results of the MPSA with those of the triangular factorization algorithm and ANSYS is undertaken to evaluate the efficiency of the MPSA. It is confirmed that the MPSA can result in a five- to tenfold increase in computation efficiency.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Bin Ye, Hailong Hu, Xiaohua Bao, Ping Lu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Instances of historical earthquakes demonstrated that sandy grounds can liquefy more than once (reliquefaction) when earthquakes occur in succession (e.g., the main shock and aftershocks). Previous laboratory experiments proved that the resistance of sand to reliquefaction might be lower after its first liquefaction despite an increase in density after the first liquefaction. To clarify the reliquefaction behavior of sand and its mesoscopic mechanism, a series of small-scale shaking table tests were performed for different shaking durations on a sand specimen to simulate multiple liquefactions. Mesoscopic images of the sand particles were taken with a stereomicroscope and an industrial camera both before and after each liquefaction. Then, a digital image processing technique was used to obtain the mesoscopic parameters of the sand particles, namely, the apparent void ratio, long-axis direction, and average coordination number. The test results demonstrated that the sand specimen could reliquefy up to three times according to various shaking durations, suggesting that the density of the sand specimen plays a significant role in the reliquefaction behavior of sand. The analysis of the mesoscopic parameters indicated that the long-axis directions of sand particles are prone to be horizontal in the initial state (before the first liquefaction), whereas after liquefaction and redeposition, the long-axis directions tend to be vertical, suggesting that the decrease in reliquefaction resistance results from the change in the mesoscopic structure of the sand.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Hasan Emre Demirci, Subhamoy Bhattacharya, Dimitrios Karamitros, Nicholas Alexander〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Fault rupture is one of the main hazards for continuous buried pipelines and the problem is often investigated experimentally and numerically. While experimental data exists for pipeline crossing strike-slip and normal fault, limited experimental work is available for pipeline crossing reverse faults. This paper presents results from a series of tests investigating the behaviour of continuous buried pipeline subjected to reverse fault motion. A new experimental setup for physical modelling of pipeline crossing reverse fault is developed and described. Scaling laws and non-dimensional groups are derived and subsequently used to analyse the test results. Three-dimensional Finite Element (3D FE) analysis is also carried out using ABAQUS to investigate the pipeline response to reverse faults and to simulate the experiments. Finally, practical implications of the study are discussed.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): Ran Fang, Zheng Lu, Hailin Yao, Xingwen Luo, Mingliang Yang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A new track-multilayer ground model was established to investigate railway subgrade dynamic responses induced by moving train load in this paper. The ground structure was modeled by an elastic layer overlying an unsaturated porous elastic half space. The dynamic governing equations of the three-phase porous medium, which are easy to be degraded to Biot's theory, were derived with consideration of both viscous drag and inertial coupling between pore fluids and soil skeleton as well as capillary pressure. The model solutions were obtained based on dynamic stiffness matrix method and Fourier transform and introducing corresponding boundary condition. The vertical displacement on the subgrade top surface and the pore water pressure along the depth were studied. The numerical results show that the effects of saturation, vehicle speed, train axle load and subgrade bed material properties on the subgrade responses are significant.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Junguo Peng, Yanpeng Zhu, Yong Zhou〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Shukla developed a generalized expression for the dynamic passive earth pressure from cohesive -frictional soil backfill by considering the equilibrium of a passive failure wedge (International Journal of Geotechnical Engineering 2013; 7(4): 443–446). In this paper, the inclined slice element approach is used to derive this expression under seismic loading conditions. Using this method, the nonlinear distribution of passive earth pressure and its application position are obtained with a few assumptions. By taking the failure surface as a plane, the analytical expression for the critical angle of failure surface is also derived. The generalized expressions can be applied to the calculation for cohesive or cohesionless backfill for specialized cases static and dynamic conditions. The total passive forces from the derived expressions are consistent with Rankine's expression, Coulomb's expression, and Mononobe-Okabe's expressions.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): W. El-Sekelly, V. Mercado, T. Abdoun, R. Dobry, A. Sepulveda〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The paper presents the implementation of an identification technique to characterize the pore pressure behavior of a silty sand centrifuge deposit subjected to more than 70 seismic shakings with full pore pressure dissipation between shakings. The seismic shakings were meant to crudely simulate the seismic history of field deposits in some very seismically active zones in California. The technique estimates shear stresses and strains based on acceleration and pore pressure recorded using a vertical array of sensors in the deposit. A constitutive model was implemented to identify optimal material parameters controlling the contractive behavior of the soil based on the recorded response of all shakings. It was found that the seismic history of soil deposits plays an important role in determining the contractive tendency of the material, significantly influencing the pore pressure response of the deposit. That is, the seismic history can reduce or increase the resistance of a deposit to contraction and liquefaction.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): Mehmet Bakır Bozkurt, Cem Topkaya〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Various replaceable link details were developed for use in steel eccentrically braced frames (EBFs) during the past decade. These details include but are not limited to bolted flush end-plated links, bolted extended end-plated links, web connected replaceable links, and bolted flange- and web-spliced links. Another detail which is based on splicing the beam outside the link and braces was recently proposed by the authors. The performance of this detail when used with directly connected braces was studied through experimental testing and acceptable performance was demonstrated. In practice gusseted attachments are widely used for connecting the braces to the beams in EBF systems. In this paper, the proposed detail by the authors is extended to replaceable links with gusseted brace attachments. The use of gusset plates enables to tailor the geometry of the replaceable link and allows different details to be developed. Three replaceable link details are proposed herein. The first detail employs standard gusset plated detail where splicing the beam is performed outside the connection region. The second detail develops a more compact replaceable link by connecting the beam to the link within the brace connection panel. The third detail is a pin connected detail where minimal amounts of bending moments are transferred to the brace member. The proposed details are studied by conducting nine nearly full-scale EBF tests under quasi static loading. The type of replaceable link, link length ratio, connection type, gap size of splice connections, demand-to-capacity ratio of members are considered as the prime variables. The inelastic rotation capacity provided by the replaceable links satisfied the requirements of the AISC Seismic Provisions for Structural Steel Buildings (AISC341-16). The links failed mainly due to fracture of the link web or flange. No failures were observed in the gusseted joints demonstrating the potential of the proposed details.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 18 September 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering〈/p〉 〈p〉Author(s): Chao Pian, Jiang Qian, Edmond V. Muho, Dimitri E. Beskos〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A performance-based seismic design method for plane reinforced concrete (R/C) moment-resisting frames (MRF) is proposed. This method is based on a hybrid force/displacement (HFD) seismic design scheme, which has been successfully applied to the seismic design of steel structures and is extended in this paper to plane RC-MRFs. The proposed HFD method combines the familiar to engineers force-based design (FBD) method, used in all seismic design codes, with the displacement-based design (DBD) method, which efficiently controls the deformation and hence the damage in a performance-based design (PBD) framework. This is accomplished by constructing explicit empirical expressions for a behavior (strength reduction) factor, which incorporates target non-structural and structural deformation metrics such as inter-storey drift ratio (IDR) and member plastic rotation (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0069.gif" overflow="scroll"〉〈msub〉〈mrow〉〈mi〉θ〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="italic"〉pl〈/mi〉〈/mrow〉〈/msub〉〈/math〉). Use of this factor in conjunction with the elastic acceleration spectrum of EC8, can produce designs in one step, by simply conducting a strength checking, since the deformation restrictions are automatically satisfied. Those expressions for the behavior factor in terms of target deformation metrics, number of storeys, column to beam strength ratios and beam to column stiffness ratios are derived through extensive parametrical studies involving 38 RC-MRFs, under 100 ordinary ground motions (25 for each of the four soil classes of EC8) for seven deformation targets. Comparison of the proposed method with the EC8 seismic design through examples, with the aid of non-linear time-history (NLTH) analyses, demonstrates its advantages.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): George A. Papagiannopoulos〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The equivalent damping concept originally proposed by Lydik Jacobsen in 1930 is revisited in order to be of use in the seismic analysis of building structures. After briefly recalling that the equivalent damping is obtained by a linearization of a frequency response transfer function and can be deformation-dependent, the paper is then focused on its potential application. In particular, the equivalent damping is employed a) to estimate the maximum seismic displacements of first-mode dominant structures, b) in linear modal analysis, c) in response spectrum analysis and d) in energy-based considerations. Examples are provided highlighting the aforementioned applications of the equivalent damping concept, aiming to retrieve the interest of the engineering community.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Mourad Zeghal, Omar El-Shafee, Tarek Abdoun〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study investigated the dynamic response and liquefaction of level saturated-sand deposits subjected to biaxial shaking using a number of centrifuge tests. Dense and loose sandy soil deposits were built in a 2D laminar container and subjected to a series of biaxial base excitations that approximate in somewhat realistic fashion the conditions of a site subjected to earthquake shaking. A dense array of accelerometers and pore pressure sensors was used to monitor the deposit response. The recorded accelerations and pore pressures were employed along with a non-parametric identification procedure to estimate the corresponding dynamic shear stress-strain histories. In turn, these histories were employed to assess the effects of non-proportional loading on soil contraction and dilation mechanisms. Pore water pressure buildup was found to be affected by load non-proportionality and a direct function of the phase angle of the induced shear stresses. The loose and dense soil deposits had contrasting as well as similar response patterns.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Bin Xu, Xingliang Wang, Rui Pang, Yang Zhou〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Amplitude, frequency content and duration are the three main features of earthquake ground motions. The first two features have been fully considered in the seismic design of high concrete-faced rockfill dams (CFRDs). However, the role of ground motion duration on the seismic performance assessment of CFRDs remains unclear. In this paper, 40 as-recorded ground motions with a broad distribution of durations modified to match a 5% damped target spectrum are selected to investigate the influence of strong motion duration on the seismic performance of high CFRDs. A generalized plasticity model for rockfill materials, a plastic damage model for face slabs and a generalized interface plasticity model to describe the relative sliding behavior between the face slabs and rockfill are adopted for the dynamic response analysis based on a 2D 200-m-high regular CFRD. The vertical displacement, horizontal displacement, plastic shear strain and a face-slab damage index are used as the dam damage measures (DMs). The correlation coefficient 〈em〉R〈/em〉〈sup〉〈em〉2〈/em〉〈/sup〉 is selected to reflect the degree of the relationship between strong motion duration and DMs. The results indicate that the vertical displacement, horizontal displacement, and plastic shear strain are positively correlated with strong motion duration, but the face-slab damage index has a low correlation. Therefore, the influence of strong motion duration should be considered in the seismic performance assessment of high CFRDs, and the use of short durations of strong ground motion in the design and seismic performance assessment of CFRDs may overestimate dam performance.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Fabrizio Scozzese, Giusy Terracciano, Alessandro Zona, Gaetano Della Corte, Andrea Dall’Asta, Raffaele Landolfo〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study illustrates an approach that allows evaluating the intensity and extent of non-structural damage in steel buildings. Different levels of cladding panel damage are introduced and a specific cladding panel hysteretic model is included in the structural model and calibrated on available data from experimental tests. Numerical results from nonlinear dynamic analyses are elaborated in the form of fragility curves for the damage limit state and used to compare the consequences of different cladding behaviours on prototype single-storey industrial steel buildings used as case studies. The outcomes are also compared to a damage limit state derived from structural analysis adopting bare-frame models and conventional drift-based damage criteria.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Ling Li, Sanjay Nimbalkar, Rui Zhong〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper proposes a three-dimensional model incorporating finite element (FE) meshes with infinite element (IE) boundaries for ballasted railways. Moving train loads are simulated with sliding motions of moving elements which have hard contact feature at the interface with supporting rails. Dynamic responses of ballasted railway under different train speeds are investigated in time domain and frequency domain to identify the predominant frequency and critical speed. Rayleigh wave (R-Wave) propagation is simulated using the combined FE-IE model to determine the velocity of R-Wave in the layered embankment model and its relationship with the critical speed of the ballasted railway. The proposed model is successfully validated against the results of Euler-Bernoulli Elastic Beam (E-BEB) model.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): Xin Liu, Jun Yang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Characterizing the small-strain shear modulus (〈em〉G〈/em〉〈sub〉0〈/sub〉) of sand with fines is of importance in geotechnical applications since natural sand is usually not clean but contains a certain amount of fines. This paper presents an experimental study to investigate 〈em〉G〈/em〉〈sub〉0〈/sub〉 values of several sand-fines mixtures, formed by mixing clean quartz sands of different sizes with crushed silica fines of varying quantity. Focus of the study is on the possible interplay between the influence of particle size disparity and the influence of fines contents for which current understanding is not adequate. By defining the particle size disparity as 〈em〉D〈/em〉〈sub〉50〈/sub〉/〈em〉d〈/em〉〈sub〉50〈/sub〉, where 〈em〉D〈/em〉〈sub〉50〈/sub〉 is the mean size of base sand and 〈em〉d〈/em〉〈sub〉50〈/sub〉 is the mean size of fines, a critical range of size disparity is found to be approximately between 4 and 7. When the size disparity is smaller than 4, the role of fines is manifested mainly by fines content; when the size disparity is beyond 7, the contribution of fines to the load transfer gradually becomes negligible because in this case fine grains tend to roll into the voids. A new concept, referred to as combined size disparity, is proposed to capture the influence of fines content and the influence of size disparity in a collective manner. By adopting this concept, an empirical relationship is proposed for estimating 〈em〉G〈/em〉〈sub〉0〈/sub〉 values of sand-fines mixtures. The predictive performance of the relationship is then examined using literature data and a reasonably good agreement between prediction and measurement is obtained.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): P. Galvín, D.López Mendoza, D.P. Connolly, G. Degrande, G. Lombaert, A. Romero〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The number of railway lines both operational and under construction is growing rapidly, leading to an increase in the number of buildings adversely affected by ground-borne vibration (e.g. shaking and indoor noise). Post-construction mitigation measures are expensive, thus driving the need for early stage prediction, during project planning/development phases. To achieve this, scoping models (i.e. desktop studies) are used to assess long stretches of track quickly, in absence of detailed design information. This paper presents a new, highly customisable scoping model, which can analyse the effect of detailed changes to train, track and soil on ground vibration levels. The methodology considers soil stiffness and the combination of both the dynamic and static forces generated due to train passage. It has low computational cost and can predict free-field vibration levels in accordance with the most common international standards. The model uses the direct stiffness method to compute the soil Green's function, and a novel two-and-a-half dimensional (2.5D) finite element strategy for train-track interaction. The soil Green's function is modulated using a neural network (NN) procedure to remove the need for the time consuming computation of track-soil coupling. This modulation factor combined with the new train-track approach results in a large reduction in computational time. The proposed model is validated by comparing track receptance, free-field mobility and soil vibration with both field experiments and a more comprehensive 2.5D combined finite element-boundary element (FEM-BEM) model. A sensitivity analysis is undertaken and it is shown that track type, soil properties and train speed have a dominant effect on ground vibration levels. Finally, the possibility of using average shear wave velocity introduced for seismic site response analysis to predict vibration levels is investigated and shown to be reasonable for certain smooth stratigraphy's.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): F. Gatti, S. Touhami, F. Lopez-Caballero, R. Paolucci, D. Clouteau, V. Alves Fernandes, M. Kham, F. Voldoire〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The scope of this paper is to give an insight into the advantages of a new, all-embracing, modeling approach of a strong ground motion scenario, by carrying out a source-to-structure analysis at regional scale, accounting explicitly for the uncertainties related to the databases and the models. To this end, a suitable case-study is represented by the 2007 Mw6.6 〈em〉Niigata-Ken Chūetsu-Oki〈/em〉 seismic sequence (west Japan), that damaged the Kashiwazaki Kariwa Nuclear Power Plant. This study describes the effect of the wave propagation path within the Earth's crust on the seismic response of nuclear reactor buildings located nearby a seismogenic source. The multiscale problem is de-coupled into three steps: (1) a parallel simulation of seismic-wave propagation throughout the Earth's crust at regional scale (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0084.gif" overflow="scroll"〉〈mrow〉〈mo〉≈〈/mo〉〈/mrow〉〈/math〉 60 km wide, major 3-D geological interfaces found below the nuclear site), reliable up to 5.0 Hz; (2) a mid hybridization step consisting in enriching the synthetic wave-field at high frequency (up to 30 Hz), employing an Artificial Neural Network to predict the short-period (SP) spectral ordinates; (3) a high-resolution structural dynamic analysis, introducing the hybrid broad-band synthetics as input wave-motion. A simplified 〈em〉stress-test〈/em〉 is performed, by simulating two small point-wise aftershocks at different source-site position. The impact of the underground 3-D geology on the structural components is finally quantified, by injecting the obtained broad-band time-histories in a Soil-Structure Interaction (SSI) model of the nuclear reactor building. The good fit obtained in terms of amplification factor at different recording stations assures the high-fidelity of the holistic philosophy endorsed.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 5 September 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering〈/p〉 〈p〉Author(s): Edmond V. Muho, George A. Papagiannopoulos, Dimitri E. Beskos〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A performance-based seismic design method is proposed for three types of plane R/C structures, i.e., moment resisting frames, infilled moment resisting frames and wall-frame dual systems. It is a force-based design method using the concept of the equivalent viscous damping ratio 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0115.gif" overflow="scroll"〉〈mrow〉〈mi〉ξ〈/mi〉〈/mrow〉〈/math〉 to account for inelastic energy dissipation instead of that of the behavior (or strength reduction) factor q (or R). More specifically, it uses equivalent modal damping ratios 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0116.gif" overflow="scroll"〉〈msub〉〈mrow〉〈mi〉ξ〈/mi〉〈/mrow〉〈mrow〉〈mi〉k〈/mi〉〈/mrow〉〈/msub〉〈/math〉 defined for the equivalent linear multi-degree-of-freedom system to the original non-linear multi-degree-of-freedom system. This equivalent system has the same mass and the elastic stiffness of the non-linear one. Furthermore, these equivalent modal damping ratios 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0117.gif" overflow="scroll"〉〈msub〉〈mrow〉〈mi〉ξ〈/mi〉〈/mrow〉〈mrow〉〈mi〉k〈/mi〉〈/mrow〉〈/msub〉〈/math〉 are constructed as functions of the periods of the structure, the target non-structural and structural deformation (both expressed in terms of inter-storey drift ratio and member plastic rotation) and soil type. Thus, the proposed method is more rational and leads to more accurate results in one step (only strength checking) than code-based design methods requiring two steps (strength and deformation checkings). In addition, it can be used as a performance-based seismic design method with two or more performance levels. Explicit expressions of these 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0118.gif" overflow="scroll"〉〈msub〉〈mrow〉〈mi〉ξ〈/mi〉〈/mrow〉〈mrow〉〈mi〉k〈/mi〉〈/mrow〉〈/msub〉〈/math〉 for the first few significant modes are proposed. These expressions have been obtained through extensive parametric studies involving non-linear dynamic analysis of 76 frames under 100 far-fault ground motions (corresponding to four soil types of EC8) for different deformation targets. These 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0119.gif" overflow="scroll"〉〈msub〉〈mrow〉〈mi〉ξ〈/mi〉〈/mrow〉〈mrow〉〈mi〉k〈/mi〉〈/mrow〉〈/msub〉〈/math〉 can be used for seismic design through linear analysis in conjunction with an elastic acceleration design spectrum modified for high amounts of damping. The proposed method is illustrated and validated by numerical examples which demonstrate its advantages over the Eurocode 8 seismic design method.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 1 September 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering〈/p〉 〈p〉Author(s): Zhongzhi Fu, Yijiang Zhang, Shengshui Chen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This discussion is based on the paper by Pang et al. [1]. In this paper, the authors made important contribution to the understanding of seismic stability of rockfill dams by considering the effects of strain softening of materials and the uncertainty of earthquake excitations. It is well known that granular materials may exhibit significant softening behaviour depending on the magnitudes of confining stresses and shear strains, and such behaviour leads to a progressive propagation of failure zones in the relevant rockfill structure. This discussion presents some comments on the definition of safety factor, the representativeness of stochastic ground motions and the range of shear strains used in the reported dynamic response analyses, implying that some further clarification and / or improvement may be needed.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Chao Zhang, Peng Deng, Wenhai Ke〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The kinematic soil-pile interaction is a cornerstone in developing seismic design procedure for piles. How to mathematically quantify this interaction has received intensive research efforts. However, to date, there is no consensus among researchers on the optimal mathematical model with sufficient accuracy and mathematical simplicity. Specifically, existing idealized models are frequently criticized as missing some important physical mechanisms, e.g., shear stresses in soil or continuity. It remains elusive to what extent these physical mechanisms contribute to the overall kinematic response. Herein, the contribution of each physical mechanism is singled out of the overall kinematic response of end-bearing piles with the aid of a continuum solution. Then, a series of parametric study shows that the contribution of each physical mechanism highly depends on the frequency, and the shear stresses in soil may contribute appreciably to the overall kinematic response.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Mohammad Hassan Baziar, Reza Karimi Moghaddam〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this research, permanent deformation of ten real earth dams were estimated using all the sliding block models and then, the errors between calculated deformations by each model and observed deformations of earth dams were presented and discussed in detail. The applied motion for estimating displacement of each dam was the recorded acceleration in the dam site. It was indicated that, conservative and non-conservative estimations of each model can be separated by Specific Energy Density and Response Ratio parameters in the time and frequency domains, respectively. It was also shown that, there is a logical relationship between the occurred earthquake-induced displacements and the specific energy density.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): Yongxiang Zhan, Hailin Yao, Zheng Lu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A semi-analytical approach is applied to investigate three-dimensional (3D) vibration in a coupled pavement and ground system subjected to a rectangular moving load. The pavement is simplified as an infinitely long orthogonal anisotropic elastic plate, and the ground materials are assumed to be multi-layered and transversely isotropic soils obeying the conditions of Biot’s dynamic poroelastic theory. The governing equations of the system are solved using the double Fourier transform, and the fast Fourier transform is used to obtain the dynamic responses in the time domain. The results show that the dynamic responses are significantly affected by the load velocity and peak or dip at the critical velocity. The variation in the dynamic response with depth as calculated by the transversely isotropic model is similar to that calculated with an isotropic model, but is significantly influenced by modulus anisotropy and soil layering. If E〈sub〉H〈/sub〉 〈 E〈sub〉v〈/sub〉 or G〈sub〉v〈/sub〉 〈 C〈sub〉66〈/sub〉, the subgrade design based on dynamic deformation control method will be unsafe when subjected to high load velocity. Instead, this calculation model for a subgrade is more appropriate for practical applications because of its incorporation of transverse isotropy.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): Guohuan Liu, Haitao Yu, Yaqiang Liu, Jijian Lian〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Simulation of multi-support (i.e. spatially variable) seismic underground motions in sea areas plays a significant role in the seismic analysis of cross-sea structures such as cross-sea bridges or subsea tunnels. However, existing approaches for predicting multi-support seismic motions mainly focus on the dry site soils without overlying surface water. This paper proposes an approach for predicting multi-support seismic underground motions in layered saturated half space under surface water, subjected to oblique incident 〈em〉P〈/em〉 waves. The transfer function in saturated soil under surface water, as the theoretical basis of the subsequent numerical simulation, is first derived based on wave propagation theory and the calculated reflection coefficients of 〈em〉P〈/em〉 wave–induced 〈em〉P1〈/em〉, 〈em〉P2〈/em〉, 〈em〉SV〈/em〉 waves in saturated soils. The derived transfer function is further employed to deduce and obtain the underground (sub-seabed) power spectral density function and response spectrum function. The two obtained functions, combined with the additional cross-coherence function, are subsequently employed to construct the cross power spectral density matrix and thus to simulate multi-support seismic underground motions. The solutions are validated against the target power spectral density, target response spectrum and target cross-coherence functions. A parametric analysis is presented where the effects of the soil thickness, the incident angle and the overlying water depth are investigated. Results show that the soil thickness, incident angle and overlying water depth have significant influences on the amplitude of transfer functions, which further affect the ratios between seismic ground and underground motions.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Nima Farhadi, Hamed Saffari, Peyman Torkzadeh〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Incorporating Soil Structure Interaction (SSI) effects can have a significant influence on responses. The aim of the present study is to estimate structural response. The ground motion imposed on the SSI system is selected in such a way related characteristics are matched with underlying soil. One hundred and thirteen Steel Moment Resisting Frames (SMRFs) are selected and concept of Beam on Nonlinear Winkler Foundation (BNWF) model is conducted. The responses of these structures are calculated under Non-linear Response History Analysis (NL-RHA) based on five types of soil and are compared with fixed-base ones. Observed that considering SSI effects leads to significant reduction in responses especially in structures constructed on soft soil. Finally, by using nonlinear regression analysis, a formula is introduced to estimate maximum and residual inter-storey drift ratio reduction factor, which is used to convert results of a structure with fixed condition to a structure with SSI effects.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 115〈/p〉 〈p〉Author(s): Dayang Wu, Bin Zhao, Xilin Lu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Rocking wall-moment frames (RWMFs), which perform well in controlling the soft-story mechanism, can achieve an enhanced performance by substituting their pinned base by a variable base rotational constraint provided by replaceable self-centering and energy dissipation devices. Rather than experiencing damage inside the moment frames, those upgraded RWMFs show a high potential towards seismic resilience by transferring damage to the replaceable base rotational constraint. The effect of this rotational constraint and the stiffness ratio between the moment frame and rocking wall on the dynamic behavior of upgraded RWMFs is investigated with the aid of an extended coupled-two-beam model proposed in this paper. In this model, the rocking wall and moment frame are represented by a linked flexural beam and a shear beam, respectively. The model replaces the fixed base of the flexural beam by a rotational spring to take the variable base rotational constraint into account. Closed-form solutions for modal displacement shapes, modal drifts, modal shear force and modal moment are derived. The model is verified with finite element analysis, and modal contributions to seismic response and drift concentration factor demand under earthquakes are investigated. It is found that within identified ranges of the rotational constraint and the stiffness ratio between the moment frame and rocking wall, a relatively good uniformity of story drift distribution is obtained and the higher modes effect caused by the full releasing of the rocking wall is mitigated. The model, the derived interstory drift spectra and drift concentration factor spectra can serve as useful tools for preliminary resilience oriented design purpose.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 114〈/p〉 〈p〉Author(s): Behshad Noori, Robert Arcos, Arnau Clot, Jordi Romeu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This article elaborates on an extension to the classical stiffness matrix method to obtain the Green's functions for two-and-a-half dimensional (2.5D) elastodynamic problems in homogeneous and horizontally layered half-spaces. Exact expressions for the three-dimensional (3D) stiffness matrix method for isotropic layered media in Cartesian coordinates are used to determine the stiffness matrices for a system of horizontal layers underlain by an elastic half–space. In the absence of interfaces, virtual interfaces are considered at the positions of external loads. The analytic continuation is used to find the displacements at any receiver point placed within a layer. The responses of a horizontally layered half-space subjected to a unit harmonic load obtained using the present method are compared with those calculated using a well-established methodology, achieving good agreement.〈/p〉〈/div〉