ALBERT

Beschreibung: Urban housing has been provided economically in many parts of the world by large panel precast building systems; in seismic regions, however, special attention must be given to the connections between panels in order to achieve the necessary earthquake resistance. In this paper a comprehensive seismic test programme of concrete panel assemblages done as part of a U.S.‐Yugoslavia cooperative research plan in earthquake engineering is described. The test structures were three‐storey assemblages of 1/3 scale concrete panels supplied by a Yugoslavian construction company; the models were about 12 ft high and 6 ft long, with the panels interconnected by various types of joint systems along their tops, bottoms and sides. Cyclic pseudostatic testing of the models was done at the IZIIS Laboratories in Skopje, Yugoslavia. A second set of models was assembled at the University of California, Berkeley from identical panels that had been shipped from the Belgrade factory; these models were tested on the 20 ft square EERC shaking table. The purpose of this paper is to compare the earthquake response represented by the two different types of test procedures. A major conclusion was that the response mechanisms in both cases were similar, with the principal deformation being opening of the panel joint at the base of the model due to overturning moments. As the rocking response continued, tension and compression failure occurred alternately at the two ends of the joint. The principal difference between the results was that pseudostatic testing imposed an increasing sequence of symmetric deformation that was independent of the damage being developed in the model, while the shaking table response was greatly influenced by the damage as it occurred—leading to significant unsymmetry. Moreover, the damage occurred in a concentrated region with the shaking table test. This difference emphasizes the fact that pseudostatic test results must be interpreted with caution because they do not fully simulate an actual earthquake response. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: A new constant head well permeameter has been designed to measure saturated hydraulic conductivities (Ks) ranging from 10−6 to 10−3 ms−1. Application to shallow soils of Western Australia in this Ks range highlighted problems with different aspects of the borehole discharge response. Firstly steady‐state borehole discharge was only reached in 13 out of 50 tests conducted. This was a consequence of the constraint placed on the volume of water storage (40 L) of the permeameter. For some non‐steady‐state cases, techniques of estimating steady‐state discharge from the available data are examined. Secondly borehole discharge was observed to increase with time in 34 per cent of cases. A satisfactory physical explanation of this phenomenon is not presently available. Other limitations in the application of the constant head well permeameter are noted. Examination of a number of recent theoretical developments in the determination of Ks led to a preference of saturated‐unsaturated flow solutions by Philip (1985) and Reynolds et al. (1985). These solutions involve the ‘sorptive number’ to which the solutions were sensitive but not critically sensitive. The theory was used to establish design criteria for the permeameter and to identify an optimum application strategy in terms of well dimensions and heads. Error estimation indicated that the designed permeameter was a practically useful field instrument. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: The link between groundwater and surface hydrology in a small headwater drainage basin in the zone of glacial deposition of southern Ontario south of the Precambrian Shield was examined for two years. The basin is situated in a discharge zone of a regional aquifer and contains a small treed spring‐fed swamp. The swamp exists because of the groundwater and has little effect on the maintenance of streamflow. Groundwater input to the swamp is an order of magnitude larger than precipitation. Groundwater of local and regional origin passes through the swamp by two routes: surface streamlets, where groundwater that emerges at specific seepage points in the swamp is conveyed over the ground surface with little interaction with the swamp itself, and by diffuse seepage in the swamp and through the bed of the stream. While the diffuse seepage input is the smaller component of groundwater it maintains the swamp's saturation. Groundwater input to the swamp from the specific seepage points and diffuse flow varies little over a year; therefore the saturation of the swamp and baseflow from the basin display little seasonal variation compared to other wetland types. The existence of the valley bottom in the headwater basin alters the seasonal and storm hydrology and is important to biogeochemical transformation of emerging groundwater. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: Dissolved organic carbon (DOC) was measured at hourly or two‐hourly intervals during more than 30 events in one forested and two moorland subcatchments of the Loch Fleet catchment in southwest Scotland. The dominantly peaty soils in the catchments resulted in small discharge‐related DOC variations within individual events, with a maximum range of about 2 mg 1−1. Seasonal variations were larger with an amplitude of 8‐9 mg 1−1 and maximum concentrations in the summer months. The forested stream had the highest mean DOC, twice as large as the comparable moorland stream in the preliming phase. Applications of lime to the catchments increased stream DOC concentrations, with the largest increases in the moorland catchments. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: The canopy storage capacity of a dry sclerophyll eucalypt forest was determined. This required destructive sampling of three major species of trees and development of a water soakage method for the measurement of water holding capacity of all above ground components. The influence of antecedent weather conditions on canopy storage capacity was assessed. It was shown that the interactive effects of leaf area and water holding capacity of all tree components were such that the estimated canopy storage capacity (0‐39 mm) was likely to change little except under extreme conditions of drought and rainfall. The effect of species composition on forest canopy storage capacity is also presented. The wetting processes are described and compared with those discussed in other studies. They are shown to be relevant to the estimation of canopy storage capacity in almost any forest. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: A seven year event‐based study partitioning of rainfall into throughfall, stemflow, and interception was conducted in a dry sclerophyll eucalypt forest and a Pinus radiata plantation. Resulting information will be of use for process modelling. Stemflow was influenced by event type, rain angle having a major effect; and the yields of the different species are compared. Tree characteristics that influenced stemflow yields are outlined and discussed. The canopy storage capacity of the eucalypt forest was determined and the influence of species composition is shown. The likely influence of climate variations is discussed. The canopy storage capacity is compared to the interception values estimated for continuous events of various sizes. The interception of the eucalypt forest and the pine plantation are compared on event basis for event size classes and on an annual basis. The comparative interceptions for continuous events are also discussed, while the effect of thinning the pine plantation on throughfall, stemflow, and interception is shown. The hydrological consequences of this study are: more informed judgment can be made about techniques for measurement of throughfall, tree structural characteristics (species related) can more adequately be considered when selecting trees for measurement of stemflow, and the stemflow yields can in some cases be better understood from the information about effect of event type. This paper deals with the influence of measurement method, species composition, and tree characteristics on the estimation of throughfall in the eucalypt forest. The site is near Canberra, lat. 35°S, 145°E, with annual rainfall about 650 mm. Two methods of measuring throughfall are compared: randomly placed, 200 mm cylindrical gauges (standard) and 50 mm square opening wedge type gauges (plastic), and randomly placed 5 × 0–22 m troughs. Despite the high placement density (150 to 225 ha−1), throughfall estimates from gauges has high variance and consistently underestimated those of the troughs, which had a total opening equivalent to 2325 raingauges (200 mm diameter) per hectare. Local concentration of stemflow into drip points provided by detaching bark pieces of one smooth barked species, Eucalyptus mannifera, is believed to be the principal cause of the lower collection and greater variance of the gauges. The low leaf area index (1–3) and large wood area of the forest together with a pendulous vertical habit of the leaves also contributed. The presence of E. mannifera is shown to substantially affect the relative values of throughfall as measured by troughs and gauges. The plastic receivers were found to underestimate rainfall or throughfall relative to the standard gauges, particularly for fine drop rainfall in multiperiod events. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: This paper presents case study applications for the hydraulically‐based geomorphologic Instantaneous Unit Hydrograph (IUH), developed by Diaz‐Granados et al. (1986). This IUH was derived as a function of watershed geomorphology and stream response to lateral inflows. This response was determined by solving one‐dimensional linearized equations of motion including a simple infiltration expression approximated by an infiltration coefficient multiplied by the streamflow discharge. Three gauged watersheds in Saudi Arabia are selected as case studies. A procedure for estimating the stream response parameters (the flow depth, the flow velocity, and the infiltration coefficient) is provided. A comparison is made between the observed and computed hydrographs and an evaluation of the IUH results and limitations is provided. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: Rainfall interception was studied during one complete year in two montane rain forests in the Colombian Andes at altitudes of 2550 and 3370 m. Additional measurements were made in a subsequent period at 3370 m, comparing two plots with different tree genera. Special attention was paid to the possible consequences of the abundant epiphytic vegetation, representing a high but spatially variable storage capacity. On an annual basis, interception amounted to 262 mm (12.4 per cent) of 2115 mm incident precipitation at 2550 m, and to 265 mm (18.3 per cent) of 1453 mm incident precipitation at 3370 m. There was no evidence for fog precipitation. The fact that, in spite of lower annual rainfall and lower evaporation rate, absolute quantity of interception at 3370 m was not lower than at 2550 m is probably related to differences in rainfall distribution and canopy storage capacities. The different responses of the two tree genera (characterized by distinct epiphyte cover) and the lower interception after prolonged wet periods support the idea that epiphytes play a significant role in the interception process. A realistic description of the water balance of such ecosystems will require the adaptation of existing interception models. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: Results from hydrometric and isotopic investigations of unsaturated flow during snowmelt are presented for a hillslope underlain by well‐sorted sands. Passage of melt and rainwater through the vadose zone was detected from temporal changes in soil water 2H concentrations obtained from sequential soil cores. Bypassing flow was indicated during the initial snowmelt phase, but was confined to the near‐surface zone. Recharge below this zone was via translatory flow, as meltwater inputs displaced premelt soil water. Estimates of premelt water fluxes indicate that up to 19 per cent of the premelt soil water may have been immobile. Average water particle velocities during snowmelt ranged from 6.2 × 10−7 to 1.1 × 10−6 ms−1, suggesting that direct groundwater recharge by meltwater during snowmelt was confined to areas where the premelt water table was within 1 m of the ground surface. Soil water 2H signatures showed a rapid response to isotopically‐heavy rain‐on‐snow inputs late in the melt. In addition, spatial variations in soil moisture content at a given depth induced a pronounced lateral component to the predominantly vertical transport of water. Both factors may complicate isotopic profiles in the vadose zone, and should be considered when employing environmental isotopes to infer recharge processes during snowmelt. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: An empirical hyperbolic scale‐dependent dispersion model, which predicts a linear growth of dispersivity close to the origin and the attainment of an asymptotic dispersivity at large distances, is presented for deterministic modelling of field‐scale solute transport and the analysis of solute transport experiments. A simple relationship is derived between local dispersivity, which is used in numerical simulations of solute transport, and effective dispersivity, which is estimated from the analysis of tracer breakthrough curves. The scale‐dependent dispersion model is used to interpret a field tracer experiment by nonlinear least‐squares inversion of a numerical solution for unsaturated transport. Simultaneous inversion of concentration‐time data from several sampling locations indicates a linear growth of the dispersion process over the scale of the experiment. These findings are consistent with the results of an earlier analysis based on the use of a constant dispersion coefficient model at each of the sampling depths. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: Direct observation of surface displacement in two New England salt marshes shows that shrinking and swelling of the sediment is an important mechanism for water storage. This mechanism accounts for 20 per cent of the total change in water content of the sediment in Belle Isle marsh, Massachusetts, and for as much as 36 per cent and 86 per cent of the total at separate sites in Sippewissett Marsh, Massachusetts. Swelling in response to infiltration appears to follow the infiltration model of Hemond et al. (1984). Shrinkage decreases the aeration of the sediment compared to soils that do not shrink, and reduced aeration represents a physiological stress to vegetation. For a given depth of water loss, e.g. one day's evapotranspiration, more shrinkage, less aeration, and higher stresses on vegetation will occur in deeper sediment deposits. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: Six stations along the Upper Rhone River above Lake Geneva were sampled by continuous flow centrifuge for recovery of suspended sediment. The samples were taken four times, once in 1982 and three times in 1983. In addition the mouth of the river was sampled in a like manner every two weeks during 1982 until August 1983. Samples were analysed for the major elements SiO2, Al2O3, K2O, MgO, Na2O, CaO, and Fe2O3; for trace elements, Zn, Cu, Ni, Mn, and Cr; for Org. C and Kjeldahl N; and the forms of phosphorus bound as Organic P (OP), Apatite P (AP), and Non Apatite Inorganic P (NAIP). The major elements and trace metals confirmed that there is virtually no change in the major geochemical characteristics of the suspended solids in the Rhone, spatially or temporally, indicating that this river is a well‐mixed sedimentary system. AP also remained consistent in concentration throughout the year. Sediment recovered during the winter low flow, low turbidity period has been designated SED 1 whereas sediment from the high flow, high turbidity summer condition of the river has been designated SED 2. Org C, OP, and NAIP show a dramatic decrease in concentration from SED 1 to SED 2. The decline is ascribed to dilution of a relatively constant supply of organic matter and phosphorus derived mainly from point source sewage treatment plants to the Rhone. This results in variable partitioning of the OP/NAIP and Org C under the different turbidity condition in the river between winter and summer. This interpretation is confirmed by a low and consistent C‐N ratio which except for March remains below 10. Higher values in March may be indicative of soil erosion during spring melt in the agricultural lands of the Rhone Valley. The estimated proportion of particulate bio‐available phosphorus is 14 per cent for SED 1 and 7 per cent for SED 2. These low values would suggest that there would be no observable direct effect on the primary production of the receiving waters of Lake Geneva, which would thus respond only to the cumulative loading of phosphorus from the Rhone River. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: Field instrumentation was designed and installed to quantify the influence of forest interception on the spatial and temporal distribution of water flux onto and into the forest soil at the plot scale. An application is presented which demonstrates that the instrumentation has the required resolution to monitor the spatial variability and dynamics of the flux processes. The observations show that spatial variability of interception may play an important role, not only in small scale soil moisture heterogeneity, but also in the hydrological response of a forested catchment at the hillslope scale. They also highlight the need of gathering more field information on the effects of vegetation on the spatial variability of soil surface water input. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: The processes of water movement through the Coombe Deposit in a chalk dry valley near Eastbourne in Southeast England were investigated using simple methods based on regular weekly measurements of rainfall, soil water content, and soil water potential. The drainage flux (recharge) through the soil was determined using the water balance method during the winter and the zero flux plane (ZFP) method after the appearance of the ZFP in the spring. The unsaturated hydraulic conductivity was derived applying Darcy's Law in a novel way using the measured potential gradients and weekly drainage fluxes. The derived conductivity characteristics were adequate to identify the flow mechanisms, to illustrate the difference in behaviour between the horizons of the soil profile, and to give some indication of pore water velocities. The mean daily drainage flux at 2.85 m depth during the recharge period from 10 October 1980 to 29 May 1981 was 1.6 mm d−1. Weekly mean rates of up to 3.7 mm d−1 were observed, but peak short term rates must have considerably exceeded this figure. It was shown that, in the lower part of the Coombe Deposit, when drainage fluxes are large, much of the flux passes through a very small proportion of the wetted cross‐sectional area of the soil. This gives rise to pore water velocities of at least 3 m d−1 at a depth of 2.85 m and 0.5 m d−1 between 0.5 m and 2.5 m depth. These results show that pollutants may be moved very rapidly through the profile in this, and similar, material. The core sampling techniques normally used to monitor pollutant movement in the chalk are unlikely to succeed in detecting this movement, not only because it is transient but also because it occupies only a very small proportion of the water filled pores. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: The effects of variations of drainage basin morphometry and relief characteristics on flood peak magnitude and time‐to‐peak are investigated using simulated stream networks. The networks are produced by three models: headward growth, systematic capture, and minimum power relaxation. Translational and kinematic wave flood routing were used to generate synthetic hydrographs. Peak discharge and time‐to‐peak are predictable to a high degree by five different sets of morphometric‐relief parameters. In order of decreasing order of importance in predictive ability the parameters characterize basin size, relative relief, basin concavity, and basin shape. Both simulated and natural stream networks exhibit strong dependence of planimetric morphometry upon basin concavity. The effect of this dependency is to increase the effect of basin concavity upon flood hydrographs. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: Soil hydraulic functions can be obtained with methods that range from complex and costly to simple and cheap. Decisions as to which is the most appropriate method for a specific application have to be based on a comparison of generated hydraulic functions. This comparison should preferably be based on a statistical comparison of practical applications calculated with the different hydraulic functions rather than on a statistical comparison of the functions themselves. In this study four different methods were used to generate hydraulic functions: (A) direct on‐site measurement, (B) measurement in soil horizons in the area, (C) use of a national data set, and (D) use of Van Genuchten parameters correlated with soil texture and organic matter content. The four methods were compared by their effect on two practical aspects of soil behaviour: (1) evapotranspiration deficit and (2) flux through a plane at 30 cm below soil surface. These two aspects are highly relevant for agricultural and environmental use. However, direct measurement is not feasible. A validated simulation model was used for the calculations and results obtained with method A were taken as a reference. Calculations were performed for three soil profiles for a period of seven years. Deficits and fluxes, calculated with the four methods to generate hydraulic functions, were not significantly different using the data of the seven‐year period. However, methods were significantly different when rainfall deficits were used as a covariable. This is true with the exception of downward fluxes in the period October until March which are most important for leaching of pollutants. The user has to decide whether differences between methods are sufficiently large to justify repeated, expensive on‐site measurements (method A) or whether an investment will be made to make standard series of curves to be used everywhere (methods C and D). Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: Seasonal soil water dynamics were measured at a fine‐textured, upslope site within the jarrah forest of southwest Western Australia and compared to the results from a coarse‐textured hillslope transect. Gravity drainage dominated during winter and early spring. This reversed in early summer and an upward potential gradient was observed to 7 m depth. A shallow ephemeral saturation zone was observed above a clay pan at 1.5 m depth. This saturation zone persisted through late winter and early spring, contrasting with the short‐lived saturation in the duricrust on the hillslope transect. The annual maximum to minimum unsaturated soil water storage was about 530 mm, 50 mm greater than the hillslope transect and higher than most values reported elsewhere in Australia. Significant soil water content changes following winter rain were generally restricted to 6 m but at one site occurred to 9 m. These depths were significantly less than the coarser‐textured hillslope transect. Soil water drying rates averaged 5 mm day−1 during extended dry periods compared to 3.5 mm day−1 on the hillslope transect. The drying rate occurred uniformly through the profile until late summer when a significant decrease in the upper 3 m was observed. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: Seasonal soil water dynamics were measured on a hillslope transect in the jarrah forest of southwest Western Australia over the period 1984‐86 using mercury manometer tensiometers, gypsum blocks, and a neutron moisture meter. The soil water potential gradients indicated downward vertical drainage flux through winter and spring. There was generally a change to an upwards flux in early summer which was sustained through to autumn. A shallow ephemeral saturation zone was identified in and above a duricrust layer, lasting up to three days after heavy, late winter rainfall. The annual maximum to minimum unsaturated soil water storage on the hillslope was approximately 400 mm to 6 m depth and 480 mm to 15 m depth. This did not change significantly in years of substantially different winter rainfall. The magnitude of seasonal soil water storage was similar to other forested areas with deep soil profiles. The depth of observable infiltration was dependent on annual rainfall. This was consistent with the observation that groundwater levels responded to rainfall over the whole hillslope in wet years but only responded on the lower slopes in dry years. The average summer drying rate of the soil profile to 6 m depth of 3.5 mm day−1 was within the range of values reported for forests elsewhere. In late summer, following an extended drought period, the drying rate decreased downslope but increased midslope. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: Depletion and recharge dynamics of soil water were studied at two forest sites in Northern and Southern Sweden during three growing seasons. At each site, having a stand of Norway spruce (Picea abies (L.) Karst), soil water potential was measured with 90 gypsum blocks in 30 profiles at depths of 6, 20, and 50 cm from the soil surface. The size of the rectangular plots was 250 m2. The large variation in soil water potential during desiccation periods extended throughout the measuring range of the gypsum blocks. The soil water potentials, at different times and depths, were log‐normally distributed during only parts of the desiccation periods. Due to the large variation and skewed distribution of soil water potentials the nonparametric Spearman rank correlation statistics was used to analyse the pattern of desiccation and rewetting of the soil. In the beginning of a dry period the topsoil was more efficiently desiccated than the subsoil at both sites. This difference lasted throughout all droughts at the southern site and was explained by a higher root density in the topsoil. At the northern site, however, there was no difference in the degree of desiccation at different soil depths during an extended desiccation period. While certain microsites tended to be more depleted than others during desiccation periods, this did not prove to be significantly correlated to the rewetting of the soil after the different droughts. There was a vertical relationship in soil water desiccation in which an accentuated water depletion at the 6 cm soil depth was followed by a similar strong depletion 14 cm lower in the same observation profile. Strongly desiccated observation profiles were not necessarily situated close to each other but seemed randomly spread over the site. There was no relationship between extracted water at any of the three soil depths in the different observation profiles and proximity to trees or tree size. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: A two‐dimensional finite element model for density dependent groundwater flow was calibrated to simulate sea water intrusion in Nauru Island in the Central Pacific Ocean. Nauru Island occupies an area of 22 km2 and supports a population of 8500. The island has been mined for its phosphate deposits and current reserves indicate that the mine has about eight years life remaining. The water supply of the island is about one third dependent on imported water which is also used as ballast on the phosphate ships. Imported water will not be available in the future, and a hydrogeological investigation shows that the island is underlain by a fresh water layer, less than 5 m thick. The freshwater layer overlies a thick transition zone of brackish water which in turn overlies sea water. Simulation of several management options shows that it is possible to substitute current importation of fresh water by careful extraction from the groundwater resources of the island. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: The role of the open standpipe Casagrande piezometer for determining soil pore pressures is still important because of its simplicity and reliability in comparison with transducer type instruments. Such factors are especially relevant when instrumentation is used on remote and inaccessible sites. The limitations of Casagrande type systems relate to poor response times, particularly in soils of low permeability, and the complexity of the normal gas bubbling equipment used to monitor and record data from this type of piezometer. The response can be improved, providing the design of the installation is taken into consideration in terms of the piezometer collection area and standpipe sizes. A simple acoustic technique has been developed by Geotechnical Monitoring Ltd, to monitor and record piezometric levels. This is based on measuring the period for the return echo of a high frequency signal; a technique widely used to focus cameras that has been found to be reliable and accurate. However, trials on landslide sites in Indonesia highlighted problems which related more to a lack of development rather than any fundamental problems in the method of monitoring standpipes. This paper describes such problems and how they might be overcome. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: Groundwater cation concentrations in relation to hydrologic flow paths were studied in the riparian forest zone of a small headwater catchment near Toronto, Ontario. Groundwater entering the riparian zone from uplands showed significant differences in cation concentrations between slope‐foot and near‐stream locations. Mean Ca, Mg, K, and Na concentrations in shallow groundwater at the upland perimeter of the riparian forest were 65‐0, 11‐2, 0‐7, and 1‐8 mg L−1 respectively. Mean Ca, Mg, K, and Na concentrations in deep groundwater flowing upwards through glacial sands beneath the riparian zone were 52‐1, 15‐1, 1‐3, and 2‐6 mg L−1 respectively. Shallow groundwater emerged as slope‐foot springs producing surface rivulets which crossed the riparian zone to the streams. Deep groundwater flowed upward through organic soils into the rivulets and also discharged directly to the streams as bed and bank seepage. Springs had higher Ca concentrations and lower Mg, K, and Na values than rivulets entering the streams. Conversely, Mg, K, and Na concentrations were higher and Ca concentrations were lower in bank seeps in comparison to rivulets. These results suggest that differences in cation concentrations in groundwater entering the streams result from initial contrast in the chemistry of shallow and deep groundwater rather than from the effects of riparian soils and vegetation. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: Data on performance of a geomorphologic rainfall‐runoff model in simulating observed flash flood hydrographs in 32 arid catchments have been analysed. The catchments, which are located in the southwest region of Saudi Arabia, vary in their size, slope of land, and characteristics of soils, and are in zones of different rainstorm characteristics. The sensitivity of the model accuracy with various catchment and rainfall characteristics has been investigated. Size, followed by rate of infiltration and slope of land, are the most effective catchment characteristics affecting the accuracy. In addition, the accuracy varies with spatial and temporal rainfall variation, total rainfall depth, and length of the dry period between two successive rainstorms over catchment. It is sensitive to temporal rainfall variation more than spatial rainfall variation, and to the dry period more than total rainfall depth. Generally, the model did not display an accuracy approaching that of the observations, especially in simulating peak flowrates in large size infiltrating catchments having high temporal rainstorm variation. Guidelines on the best use of the model in arid catchments were proposed. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: Stemflow of a dry sclerophyll eucalypt forest and a nearby Pinus radiata plantation was studied on a rainfall event basis. The stemflow yields of the forests are quantified, compared, and presented on an annual basis for four years. Yields of the individual eucalypt species are compared and the tree characteristics responsible for the yield differences are discussed. The influence of event size, type, and season on stemflow are also shown. Rainfall angle is shown to have a significant effect on stemflow yield. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: The heat pulse method was used to estimate stand transpiration from a radiata pine (Pinus radiata) plantation in southeastern Australia over a period of four days. The diurnal pattern of sapflow was related to net radiation with a time lag of about 1.5 hours. Despite high soil moisture levels, sapflow did not keep up with evaporative demand in the afternoon. Sapflow estimates of transpiration exceeded estimates for evaporation based on Bowen ratio measurements for all four days of the study. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: A single large volume water sample taken at the mouth of the Upper Rhone River on Lake Geneva was processed directly in parallel through two continuous flow centrifuges, a Westphalia and an Alfa‐Laval. Sediment was recovered from the Westphalia, and separately from the bowl and brass core of the Alfa‐Laval. The three sediment samples were analyzed for particle size and the following elements: Zn, Cu, Mn, Cr, P, Co, B, V, Be, Sr, Na, Pb, Ni, Ba, Fe, Ca, and Mg. Results indicate that the particle size recovery of both machines is similar when sediment from the brass core and bowl of the Alfa‐Laval are combined, and that the recovery for all elements other than Cu, V, B, and Pb are the same when the particle size differences are taken into account. Sediment from the Alfa‐Laval brass core is clearly contaminated by Cu, B and is also elevated in V and Pb but not to a significant extent. The sediment recovered from the bowl of the Alfa‐Laval is contaminated only with Cu, with a 10 ppm increase over the 52 ppm recovered in the Westphalia sediment. Operating procedures involve the discarding of the brass core sediment and the mixing of the Alfa‐Laval bowl sediment with that from the Westphalia. The consequent increase in Cu is estimated at less than 5 ppm or within the confidence level of the analysis. These procedures are recommended to all operators of non modified Alfa‐Laval units. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: A study of partitioning of rainfall into throughfall, stemflow, and interception was conducted in a dry sclerophyll eucalypt forest and an adjacent pine plantation over a period of seven years, on a rainfall event basis. The following three issues are discussed: (1) the relationship between canopy storage capacity and interception of continuous events, (2) interception, throughfall, and stemflow, and (3) the effect on interception of thinning the pine plantation. The canopy storage capacity/interception interaction for the eucalypt forest was assessed by comparing a gravimetric estimate of canopy storage capacity with interception. The maximum possible value for canopy storage capacity was found to be a small proportion of interception for events of all sizes. This suggests that evaporation of intercepted water during the continuous events was responsible for most of the interception. This ‘within event’ evaporation appears to be responsible also for the net rainfall/gross rainfall estimate of canopy storage capacity being four times the gravimetric value. For the pines the regression estimate was more closely related to interception. Interception, throughfall, and stemflow of these forests were measured for four years. Data are presented for each year with overall average interception being 11‐4 per cent of precipitation for the eucalypt forest and 18‐3 per cent for the pine plantation. Topography and rainfall event type are considered in the comparison. Species composition and tree type are considered when comparing these results with published studies from similar forest types in southeastern Australia. The periodic (annual) variations of interception in this and the other studies makes comparison difficult. The effect of thinning on the throughfall, stemflow, and interception in a Pinus radiata plantation is examined. Throughfall increased, interception decreased but not in proportion to the removed biomass; stemflow decreased on an area basis, but increased on a per tree basis. A positive relationshiip is established between interception and stemflow on the thinned plantation but not in the unthinned. Reasons for this are suggested. The results are compared to those reported from similar experiments in other forests. The periodic variations in interception and errors inherent in its estimation suggest that caution should be exercised when using average interception figures in water balance studies. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: A large groundwater system in the Amadeus Basin, central Australia, discharges to a chain of playa lakes 500 km long. The playas contain highly concentrated brines; these are sodium‐chloride rich waters with appreciable magnesium and sulphate and very low concentrations of calcium and bicarbonate. Gypsum, glauberite, and other evaporite minerals are precipitating in the playas. The groundwaters evolve to brine by concurrent processes of dissolution, evaporative concentration, mineral precipitation, and mineralogical change. Chemical evolution is considered with reference to a concentration factor based on chloride. Ion transfer calculations demonstrate losses of magnesium and bicarbonate throughout, as a result of precipitation. Sodium, potassium, calcium, and sulphate are gained initially as a result of dissolution but lost subsequently as a result of precipitation. Larger playas in the chain, exemplified by Lake Amadeus, have dual shallow and deep groundwater flow paths whereas the smaller playas, exemplified by Spring Lake, have only shallow flow paths. Brines in the larger playas are diluted by deep groundwaters and this is reflected in the degree of saturation attained with respect to particular minerals. Thus, saturation with respect to gypsum and glauberite is attained earlier in Spring Lake than in Lake Amadeus. Saturation with respect to halite is attained in Spring Lake but not in Lake Amadeus. Both playas are undersaturated with respect to hexahydrite and sylvite although these minerals occur in efflorescent crusts in Spring Lake. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: A previous hydrometric study of runoff production in tussock grassland drainage basins in Otago (45°50′S, 169°45′E), New Zealand, revealed a marked change of slope in storm hydrograph recessions. An environmental isotope study was initiated to investigate the runoff mechanisms operating and to test specific hypotheses to explain this break in the hydrograph recession. The results indicated that for quickflow volumes in excess of 10mm, the first part of the storm hydrograph can be attributed to two separate sources, namely, ‘old’ water from a shallow, unconfined groundwater reservoir and ‘new’ water from saturation overland flow on the lower wetlands of concave slopes. Despite the extensive area of wetlands, ‘old’ water runoff from the unconfined groundwater reservoir is delivered more rapidly to the stream than ‘new’ water from saturation overland flow. Substantial surface storage in the wetlands has first to be exceeded before rain becomes a significant part of stream discharge. For quickflow volumes less than 10mm, only ‘old’ water from groundwater contributes to the first part of the hydrograph recession. This means that only the largest 7 per cent of storms (in terms of quickflow volume) generate quickflow containing significant amounts of ‘new water’. The second part of the recession of the storm hydrograph consists of ‘old’ water derived from a remarkably well‐mixed shallow unconfined groundwater body. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: This paper considers a solution method for viscously damped linear structural systems which are subjected to transient loading. The equations of motion of such systems are written in a first‐order form. A solution subspace is generated using the damped dynamic matrix and the static deflection from the first‐order form of the equations of motion. Two convenient bases, Lanczos vectors and Ritz vectors, are constructed from this subspace. An approximate solution is then obtained by superposition of the Lanczos vectors or the Ritz vectors. In contrast to the traditional mode superposition method using complex eigenvectors, the Lanczos vectors or the Ritz vectors are less expensive to generate than the complex eigenvectors, yet yield comparable accuracy. In addition, there is no need for a static correction since the static deflection is already contained in our solution subspace. Numerical examples are presented to show the potential of using the Ritz vectors to compute responses of damped dynamic systems. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: The solution of the problem of vibration of linearly elastic structures, caused by stochastic excitation of non‐interrupted, jump‐discontinuous character, is considered in the paper. Two types of excitation are examined. They form an enhancement of the continuous model which is most often used. The solution in the form of expected values, correlation functions and spectral densities of the deflection of the structure is formulated. Examples illustrating the solution are presented. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: The concept of fractional derivatives is employed in the formulation of a stress‐strain relationship for elastomers. An oscillator consisting of a mass and a ‘fractional’ Kelvin element is used to model elastomeric bearings used in base isolation systems. Efficient numerical multi‐step schemes are developed for the dynamic analysis of a single‐degree‐of‐freedom ‘fractional oscillator’ in the time domain. Numerical examples show that these multi‐step schemes are in good agreement with the Laplace and Fourier solutions. When applied to shaking table tests of a base‐isolated bridge deck, the fractional derivative model is found to agree well with the experimental results. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: [No abstract available]

Beschreibung: In this paper a theoretical and numerical analysis on the robustness and the practical feasibility of a control system of an experimental model of a building structure is performed. This model has a mechanical actuator employing active cables and the control algorithm is based on a predictive strategy. In order to test the robustness one simulates numerically different control experiments under two kinds of non‐ideal conditions: (i) discrepancies between the parameters of the system (mass, natural frequencies and the time delay in the actuator) and those assumed in the formulation of the control algorithm; (ii) operation of the active cables out of the operation range caused by excitations stronger than expected. In order to assess the feasibility, in every control experiment one obtains the values of four performance indices which provide full information about the features of the control action. The numerical results show that predictive control by active cables is robust and feasible. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: A three‐dimensional seismometer array was installed in the Chiba Experiment Station of the Institute of Industrial Science, University of Tokyo in 1982. The array system consists of 44 three‐component accelerometers densely placed both on the ground surface and in boreholes. A complementary system for the measurement of ground and buried pipe strains was also installed at the same site. The array system has been successfully in operation, and more than 160 earthquakes have been recorded. Considering a wide use of these seismograms, the Chiba array database has recently been created comprising twenty‐seven major events. This paper describes the Chiba array system and its strong motion database. Results of engineering analysis using the selected records are also presented. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: Non‐linear seismic soil‐structure interaction is studied through a hybrid procedure using the pseudo‐dynamic testing (PDT) method which is modified to take into account frequency dependence and developed for foundation‐soil systems. The numerical scheme used in conventional PDT is improved by introduction of a time‐dependent pseudo‐forcing function which is derived from frequency‐dependent dynamic characteristics of the system by means of Hilbert transformation in the frequency domain. Surface, shallow and caisson foundation models that differed in size and depth of embedment were used. The mechanical characteristics of the systems were determined from static and forced vibration dynamic tests. An amplitude scaling technique was used for three recorded accelerograms. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: The seismic analysis of a reactor building on a sliding‐type base isolation is performed by way of the hybrid frequency‐time‐domain procedure. The frequency dependence of the foundation stiffness coefficients is duly accounted for in the analysis, although the problem is non‐linear. The response results are shown to be reliable by way of comparison with the results of a time‐stepping algorithm in the specialized case of constant foundation stiffness coefficients. The fact that such an analysis can be performed is an outstanding result, particularly when considering that no difficulties are encountered in the implementation and in the calculation. The flow chart used to implement the procedure is presented in the paper. The reactor building is analysed for three different sites with each site having three sets of material properties. It appears that the structural response is not strongly affected by the frequency dependence of the foundation stiffness coefficients. This also holds true as far as the response of equipment attached to the superstructure is concerned. For all practical purposes this frequency dependence may be disregarded in favour of constant spring and damping coefficients. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: We propose an effective and reliable time‐domain substructure technique which takes soil‐structure interaction effects into account and uses the flexibility coefficients of unbounded soil obtained in the frequency domain. Compared with previous methods, the frequency points to calculate flexibility coefficients, and computational loads in the calculation of time‐domain interaction forces, are reduced. In the formulation, we have assumed the flexibility coefficient to be a periodic function, obtained within the bandlimited frequency range, which also includes the predominant frequencies of the structure and incident wave. Then we simulate the periodic flexibility coefficients using discrete impulse responses in the time‐domain analyses. However, the real and imaginary parts of the bandlimited flexibility coefficients do not form a Hilbert transform pair; the discrete impulse responses should be modified to be causal for the time‐domain analyses. We present various discrete impulse responses which have been obtained from only the real part, only the imaginary part and from both the real and imaginary parts of the frequency‐domain flexibility coefficients by FFT with causality conditions. Through a numerical example the relationship between the modified discrete impulse responses and the validity of the time‐domain substructure method is presented. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: The optimum design of seismic structures equipped with active controls is presented. The design variables are structural parameters, such as structural stiffness or moment of inertia. The optimization procedure is carried out in two stages. First, the optimal control forces are expressed in closed form, as implicit functions of the design variables. In the second stage, the structural parameters are varied in order to minimize a structural weight objective function. The algorithm is applied to structural systems under earthquake excitations, for displacement, frequency and control force constraints. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: [No abstract available]

Beschreibung: In the present paper a two‐degree‐of‐freedom system is considered which allows the simulation of rigid blocks uplifting and sliding on frictional foundations; the monolateral constraint between block and base is schematized by means of a joint model, which allows the contact problem to be discretized. The joint model is governed by normal and shear constitutive laws, which have been derived by the phenomenological behaviour of stone blocks and rock joints, as given by rock mechanics. Furthermore, a numerical procedure has been developed in order to solve the non‐linear equations governing the motion of the block‐base system, and to analyse the dynamic response of this system under seismic excitation; particular attention has been paid to the influence of the vertical displacement on the slip response. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: A relatively simple and straightforward procedure is given for representing analytically defined or data‐based covariance kernels of arbitrary random processes in a compact form that allows its convenient use in later analytical random vibration response studies. The method is based on the spectral decomposition of the random process by the orthogonal Karhunen‐Loeve expansion and the subsequent use of least‐squares approaches to develop an approximating analytical fit for the data‐based eigenvectors of the underlying random process. The resulting compact analytical representation of the random process is then used to derive a closed‐form solution for the non‐stationary response of a damped SDOF harmonic oscillator. The utility of the method for representing the excitation and calculating the mean‐square response is illustrated by the use of an ensemble of acceleration records from the 1971 San Fernando earthquake. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: Seismic damage to segmented buried pipelines is investigated in this paper. Information on their performance during past earthquakes is reviewed briefly. An analytical model for evaluating the response of long straight runs of segmented buried pipelines to seismic wave propagation is presented. It takes into account the non‐linearity as well as the variability of the system characteristics. Also, results from laboratory tests by others are used to establish the relative joint displacement which leads to leakage. These two elements are combined to predict the damage ratio (number of leaks per kilometre) for cast iron pipes with lead caulked joints subject to a joint pull‐out failure mode. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: The experimental work and first results of a recently completed experimental research programme investigating the response of reinforced concrete (RC) walls under earthquake (EQ) loading are discussed in this paper. A brief literature review is given as a prelude to the outline of research objectives. The tests are presented in two groups according to the scale of models. For the 1:5 scale tests, a modified similitude relation for small scale reinforced concrete dynamic modelling is developed. Based on the chosen model parameters, the design of the isolated RC walls is given. The test‐rig set‐up and the EQ input signals suitable for testing the model on the Imperial College shake‐table are also discussed. Preliminary observations regarding stiffness, strength and failure modes of the RC wall models are given. Experimental results from the shake‐table are compared to tests, at the same scale, under static cyclic conditions. For the scale 1:2–5 cyclic tests a different test‐rig assembly is designed. The test results are given in three pairs of flexurally similar walls followed with general observations and discussion. Finally, conclusions are drawn regarding experimental procedures and behaviour patterns of the tested models. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: The error‐propagation characteristics of an implicit time integration algorithm in pseudodynamic testing are examined. It is shown that the implicit algorithm is superior to explicit integration algorithms in terms of experimental error amplification. The influence of systematic experimental errors is studied and methods for controlling these errors are examined. In spite of the fact that the implicit algorithm is unconditionally stable, it is shown that the integration time interval in a pseudodynamic test is limited by the calibration range of the electronic hardware as well as the degree of participation of the higher modes. Furthermore, the tolerance for experimental errors decreases as the integration time interval increases. Copyright © 1990 John Wiley & Sons, Ltd

Beschreibung: The purpose of the paper is to study the vibrational characteristics of the Flaminio Obelisk in Rome as part of general studies being performed for preservation purposes. The scope of the paper is limited to dynamic analysis using a finite element model and comparison of the results with those from the measured response to forced vibrations. The state of preservation of the monument is described as well as the sonic method used to evaluate the integrity of the sections. The results of the sonic tests are used to determine reductions in the cross‐sectional properties. A stick model including two rotational frequency independent soil springs at the basement level of the obelisk is developed. A good agreement between the numerical and the experimental results is obtained for the natural frequencies and for the modal shapes. A response spectrum and stress analysis according to the Italian Seismic Code is performed considering and evaluating the degraded characteristics of sections. Copyright © 1990 John Wiley & Sons, Ltd