ALBERT

Notes: Conclusions 1. Experments with cyclic temperature-induced deformation of structures on an earth slope confirmed the phenomenon of their sliding. With increase in the number of cycles under constant static conditions this process tends to fade away. A study of the physical picture of deformation showed that local upward yielding and expansion of the soil in the end zone of the slabs play the main role in the accumulation of residual displacements. 2. An analysis of the experimental data permits recommending for further study a pile-free foundation under large-diameter pipelines with the construction of a projection in the center of each section and with artificial removal of friction in the end zones.

Notes: Conclusions 1. The characteristics of elasticity and creep of mature concrete under uni-, bi-, and triaxial compression in the region of linear creep do not depend on the type of stress state and can be determined in ordinary uniaxial experiments. 2. The assumption of equality of Poisson's ratios of elastic strains and creep and their constancy in time made in the linear theory of an elastically creeping body is admissible. 3. The usual assumption of independence of the action of forces in various directions with consideration of Poisson's strains (e.g., the generalized Hooke's law) is confirmed by experiments with the long action of time-constant compressive stresses not exceeding 30–40% of the ultimate strength.

Notes: Conclusions 1. The original calculation scheme in which the entire static load from the conduit is transmitted to the capping beams does not take into account practically the combined work of the entire structure of the conduit. To provide the combined work of the conduit and capping beams it is necessary to limit the initial opening of the joints due to shrinkage and temperature variations to 0.4–0.5 mm. As the calculations show, this is feasible even at the maximum possible rate of the works. 2. The rigidity of the interacting structure of a large-diameter conduit and pile grillage is considerably higher than the rigidity of capping beams, which leads to a decrease of forces in the capping beams and increases the bearing capacity and reliability of the conduit. Consideration of the combined work of the conduit and pile grillage makes it possible to reduce the consumption of reinforcement in the capping beams and to equalize the deformations of the foundation within the section. 3. The combined work of precast elements of a concrete-encased steel conduit of a pumped-storage station and pile grillage is provided by welding the embedded parts of the precast elements and capping beams, and also by high-quality sealing of the joints between elements. The static work of the precast structure in this case becomes close to the work of a monolithic structure.

Notes: Conclusions 1. In the tensioned zone equal to the depth of the cracks observed in the experiments a rectangular water pressure diagram is at first established, but after several days due to losses of pressure as a consequence of seepage along partially clogged cracks the pressure diagram becomes less rectangular, and pore water pressure equal to 30–50% of the pressure head occurs in the compressed zone. 2. Investigations of the reinforced-concrete elements under the effect of the uplift pressure of water in one crack showed that in this case the change in stresses in the reinforcement occurs only in the section along this crack and has a local character, so that outside the zone of action of the water pressure its effect on the internal forces in the reinforced concrete element rapidly diminish on a length of 0.3–0.4 h. 3. In the zone of action of water pressure encompassing a system of 7–9 normal cracks changes in the stress state were observed mainly in sections along the extreme cracks. In the other sections the changes were 2–5 times less. The measured values of the increments of stresses in the reinforcement in sections along the extreme cracks from the effect of a water pressure of 5–8 gauge atm were close to the calculated values of such increments obtained according to the existing standards, in conformity with which these increments should be taken into account in any section of non-crack-resistant reinforced-concrete elements. At the same time, the values themselves of the stresses in the reinforcement obtained from experiments substantially differ from the calculated values obtained both with and without consideration of the water pressure.

Notes: Conclusions 1. To eliminate the joint between the upstream zone of ordinary concrete and internal zone of rollcrete, a design of a gravity dam is proposed with the construction of a sawtooth joint between these zones, which is obtained by tiered placement at first of 2–4 layers of rollcrete and then concrete of the upstream zone with the use of the layerwise method. The joint of the two types of concrete is carried out through the inclined area of undercompacted lean concrete, which is formed naturally along the slope of 2–4 layers of lean concrete mix having an average gradient of 1∶0.1 toward the upstream pool. On the next tier up the joint of the two concretes is shifted toward the upstream face, which creates localness of the undercompacted areas of concrete and, on the whole, the sawtooth shape of the contact of the upstream and internal zones of the dam. 2. On the downstream face it is suggested to protect the rollcrete with an insulating layer made of triangular precast reinforced-concrete elements, inside which is located insulation. The tiered installation of the precast elements with rolling of 2–4 layers of lean concrete on them creates the sawtooth joint between the internal and downstream zone of the dam, providing minimum effects of the outside air temperature fluctuations on the load-bearing profile of the structure. 3. The proposed design of the dam allows uniform tiered placement of the concrete, and two methods of concreting: rolling of the lean concrete and vibration by the suspended packet vibrators can be separated within the tier so as to maximally simplify the technology of constructing the dam. The layerwise method of concreting the upstream zone of the dam and the method of rolling the lean concrete in the internal zone coincide in many technological operations, which on the whole enables their successful combination when constructing the dam and creates favorable conditions for providing solidity of the structure. 4. In further investigations it is necessary to calculate the stress state of the dam with variation of the location of the contact between the zones of concrete of different type in plan and over the height. In a particular development of the design of a dam with a downstream insulation zone, investigations of the effect of the thickness of the insulation zone on the calculated profile of the dam, accompanied by the selection of the type and thickness of the insulation material in relation to the climatic conditions of the construction region, will also be required.

Notes: Conclusions 1. Rollcrete has creep, the general regularity of the development of which in time and as a function of the age of the concrete can be described by the formula proposed earlier by Aleksandrovskii and widely used for ordinary concrete. 2. As for the quantitative side of the problem, the presently available scanty data on creep of rollcrete indicate that its creep is higher than creep of ordinary concrete. 3. Formula (1) can be recommended for calculating the stress and thermal stress states of rollcrete masonry with consideration of creep; for engineering calculations, stress relaxation coefficients were obtained and are represented for rollcrete of class V10 by a family of curves convenient from the viewpoint of practical use.

Notes: Conclusions The experience of developing and introducing a computer information diagnostic system for monitoring the safety of hydraulic structures at the Volga-Lenin hydrostation showed that the new technology and computing machinery make possible a fundamental change in the established practice of on-site observations and have imparted to them functions of a key link in the process of routine monitoring of the state of structures and safe operation of the hydro development. This factor has special significance for structures that have been operating for decades and naturally acquired an increased hazard and vulnerability to the effect of the environment and aging processes of materials, structural members, equipment, and monitoring and measuring equipment. A change to computer technology of monitoring the safety of structures of hydrostations is justified both under conditions of the continuing operation of MME installed earlier without the possibility of its automatic polling and under conditions of replacing the equipment with newer measuring tools substantially increasing the efficiency of monitoring the state of structures.

Notes: Conclusions 1. New, more reliable data were obtained on the relaxation of stresses in hydrotechnical concrete of various grades, the use of which in designing massive concrete structures permits approximating the data of theoretical and model investigations to the real working conditions of concrete in the structure. 2. Aging of concrete has a quite substantial effect on the degree of stress relaxation; e.g., it differs by a factor of 2–3 for concrete at an age of 3 and 500 days. The effect of aging of concrete on the stress relaxation coefficient must be taken into account to to an age of at least 180 days. Concrete at an age of 3 days is characterized by limiting values Kr(∞, τ) that are close for all three grades and equal on the average to 0.25. Concrete of a mature age is characterized by limiting values of the relaxation coefficient of 0.54 for grade 200 and 0.64–0.67 for grades 300 and 450. 3. Despite the fact that the data obtained on stress relaxation pertain to three specific compositions of concrete of the Toktogul and Inguri dams, the identity and comparatively little difference of the relaxation curves (e.g., for concrete grades 300 and 450) permit recommending their use in engineering calculations of structures being designed with analogous concrete.