No 6 (2017)

A spatial system of two closed cylindrical shells is considered, having rigid fixation at one end and a free end at the other. Shells are located at some distance from each other and are interconnected by one intermediate link. One of the shells is under the action of a load, concentrated in the annular direction and uniformly distributed along one generatrix. To cal- culate the spatial system, the force method is used. Thus, the calculation of the spatial system is reduced to the calculation of individual closed cylindrical shells. From the condition of equality of radial displacements at the point of contact of the shells, the reactive pressure in the intermediate bond was determined. The magnitude of the reactive pressure in the bond varies depending on the location of the intermediate bond and the geometric parameters of the shells. Knowing the magnitude of the reactive pressure, one can determine the stress-strain state of each shell

The proposed work identified and analyzed the errors in the theory of viscoelasticity of concrete in international norms for concrete and reinforced concrete, new equations of the theory of creep of concrete, taking into account the instant nonlinearity, nonlinear creep and inertial properties of concrete. The results of the study are brought to the charts and tables, convenient for use by ordinary designers. The article was written in accordance with the recommendations of the round table, held at RUDN University on June 9, 2016 under the guid- ance of Doctor of Technical Sciences, prof. S.N. Krivoshapko.

The Scientific-and-Research Institute of Building Physics (NIISF), Moscow, Russia **TzNIISK named after V.A. Kucherenko (AO “NITz “Stroitel’stvo””), Moscow, Russia Relationship between value of loading and mechanical characteristics of structured materials is explored. A uniform analytical description of creep for stages of stable deformation, damped at time, stable and unstable critical deforming are introduced into practice for the first time

The concept of preservation of the earth's surface from destruction is realized in the present work through regulating the stresses by coordinating the processes of excavating the ore in time and space according to the criterion of stress minimization. Justification of technological solutions that ensure the preservation of the massif and the earth's surface above it due to the phenomenon of residual strength of disturbed rocks is the purpose of the article. The goal is achieved through analysis of mining practices, established behavior patterns of massifs with a discrete gravity-tectonic structural stress field and methods to ensure their stability by creating conditions for locking rocks within the dome of natural equilibrium. It is shown that the geomechanical balance of discrete rock structure is provided due to the residual bearing capacity of naturally and technologically depleted rocks. A solution is proposed for the prevention of critical stresses and their corresponding deformations by dividing the mine field into areas with a flat roofing, within which cost-minimized technologies can be applied. It is recommended to supplement the criterion of repayment optimality with the amount of compensation for damage to the environment. The typification of the mines depending on stability and disturbance of massifs is given. The condition of the solidity of the massif at various stages of existence is formulated - the condition of the geomechanical balance of the geomechanical system. The workings can be typified according to the stability, depending on the size of the structural blocks of rocks in the roof. The new classification of backfilling technologies with taking into account the phenomenon of rock blocks locking is proposed. Due to the residual bearing capacity of naturally and technologically depleted rocks, under underground mining of deposits there are rock constructions whose properties are corrected by dividing the mine field into geomechanically balanced sections with flat roofing

Researches carried out in Benin allowed the use of Borassus aethiopum mart as reinforcement in concrete. The aim of this study is to examine the bond of the two materials. The results of pull out tests have shown that the bonding strength is around 1 MPa. This adhesion rate decreases slightly when the bond length increases; on the other hand, the adhesion rate increases slightly when the concrete strength increases. The behaviour of Borassus / concrete interface shows a first phase of perfect adhesion followed by a second phase of progressive loss of adhesion and a final friction phase which continues until the complete output of the reinforcement from the concrete.