ESTIMATION OF THE FAILURE PROBABILITY OF A REINFORCED CONCRETE BEAM LYING ON A STOCHASTIC ELASTIC BASE WITH TWO PRESSURE COEFFICIENTS, ON AN INCLINED SECTION FROM THE LATERAL FORCE

The estimate of failure probability on the inclined section from the action of transverse forces, as well as the total probability of the limit States of reinforced concrete beams with probabilistic strength parameters lying on an elastic Foundation model V.Z. Vlasov-P.L. Pasternak, possessing stochastic properties. Probabilistic characteristics of the transverse force and its distribution density are constructed for a Foundation beam resting on an elastic base with two random characteristics, loaded with a quasi-stationary random load, taking into account the probabilistic nature of the strength properties of concrete and reinforcement. It is shown that if the spectral densities of the bed and load coefficients are fractional rational functions, the deflection correlation functions and, accordingly, the deflection variance are calculated using the residue theory.

RESTRUCTURING IN RESIDENTIAL AREAS AND TRANSFORMATION OF THE URBAN SPACE OF THE METROPOLIS

The article considers the developed model of the closed-cycle economy, which, along with economic parameters, takes into account pollution and consumption of building materials suitable for recycling. The model reflects the idea that the economic growth of a society alone cannot maintain or improve the existing quality of the environment, and for this it is necessary to increase the recycling rate. The purpose of the study is to reveal the factors influencing the increase in the level of recycling when introducing efficient and environmentally friendly systems for managing construction waste in megacities. The results of the study will affect the improvement of the quality and standards of life of the city population, the creation of favorable conditions for a safe, healthy and the prosperous life of people while ensuring the economic growth of the city. The process of the managing the growing volume of construction waste is reflected, recycling is emphasized.

RELATIONSHIP OF MAXIMUM DEFLECTIONS AND NATURAL FREQUENCIES VIBRATIONS OF ISOTROPIC CIRCULAR PLATES WITH INHOMOGENEOUS RESISTANCE CONDITIONS ON THE OUTER AND INNER CONTOUR

The relationship between the maximum deflections from a static uniformly distributed load W0 and the fundamental frequency of natural transverse vibrations of a round isotropic plate of linearly variable thickness with thickening to the edge under homogeneous conditions of support along the outer contour, depending on the ratio of the thickness of the plate in the center to the thickness along the edge, is considered. According to the results of the study, graphs of the dependence of the maximum deflection and the frequency of natural vibrations of the plate on the ratio t1 / t2 are constructed. It is shown that for round plates of linearly variable thickness at t1/t2<1.1 coefficient K with an accuracy of 5.9% coincides with the analytical coefficient for round plates of constant thickness. Numerical studies shows that when the ratio of the thicknesses on the contour and in the center is equal to two, the difference in the coefficient K, which depends on the relationship between the static and dynamic characteristics of the platinum, is about 25% for hinged support along the contour and up to 37% for rigid support. This indicates a more significant effect of uneven mass distribution for such boundary conditions.

STIFFNESS OF REINFORCED CONCRETE STRUCTURES UNDER BENDING WITH TRANSVERSE AND LONGITUDINAL FORCES

The authors developed a model for single reinforced concrete strips in block wedge and arches between inclined cracks and approximated rectangular cross-sections using small squares in matrix elements. From the analysis of the works of N.I. Karpenko and S.N. Karpenko the "nagel" forces in the longitudinal tensile reinforcement and crack slip , as a function of the opening width and concrete deformations in relation to the cosine of the angle . The experimental " nagel " forces and crack slip dependences for the connection between and in the form of an exponent for the reinforcement deformations and spacing are determined. The forces have been calculated for two to three cross-sections (single composite strips) of reinforced concrete structures. On the bases of accepted hypothesis, a new effect of reinforced concrete and a joint modulus in a strip of composite single local shear zone for the difference of mean relative linear and angular deformations of mutual displacements of concrete (or reinforcement) are developed. The hypothesis allows one to reduce the order of the system of differential equations of Rzhanitsyn and to obtain in each joint the total angular deformations of concrete and the "nagel" effect of reinforcement. The curvature of the composite bars has a relationship from the total bending moment of the bars to the sum of the rigidities. The stiffness physical characteristics of the matrix from the compressed concrete area and the working reinforcement are obtained in a system of equations of equilibrium and deformation, as well as physical equations.

TRANSVERSE BENDING AND FREE VIBRATIONS OF ELASTIC ISOTROPIC PLATES IN THE FORM OF ISOSCELES TRIANGLES

This paper considers elastic isotropic plates in the form of isosceles triangles with combined boundary conditions (a combination of hinged support and rigid restraint conditions along the sides of the contour). Calculations were performed using FEM to determine the integral physical characteristics in the considered problems F (the maximum deflection of uniformly loaded plates w0 and the fundamental frequency of oscillations in the unloaded state ω). On the basis of the obtained numerical results, approximating functions have been constructed: "maximum deflection - form factor of plates", "basic frequency of oscillations - form factor of plates", the structure of which corresponds to the structure of similar formulas obtained when presenting known exact solutions in the corresponding problems of technical theory of plates in isoperimetric form. Based on the properties of the form factor of plates, these approximating functions limit the whole set of considered integral physical quantities and therefore can be used as reference solutions for the calculation of triangular plates of arbitrary form applying the method of interpolation by form factor (MIFF). We consider an example of calculation of a plate in the form of a rectangular triangle with hinged support of the sides.

RESERVE OF ANALYTICAL SURFACES FOR ARCHITECTURE AND CONSTRUCTION

After a period of relative calm in the construction and design of thin-walled large-span shells and network multilayer shell structures, which, according to the world's leading architects, began in the 1980 s, the time has come for the expanded use of spatial structures in the architecture of public and industrial buildings. Less commonly, shells are used in small-sized housing construction: ecological villages, noospheric and bionic architecture. The entire 20th century did not stop research on the development of analytical and numerical methods for analyzing shells for strength and stability, for the creation of new building materials. Geometers have created and studied more than 600 analytical surfaces that can be mistaken for the mid-surfaces of civil and mechanical engineering shells. As a result, by the beginning of the 21st century, architects and engineers had all the necessary tools to continue the traditions of the "golden age of shells". The analysis of problems with the use of new forms in parametric architecture, carried out in the article, showed that more than ten classes of surfaces from their classification have not yet found application in architecture and mechanical engineering. It is assumed that the number of applied classes of surfaces will not expand, and new ideas for the shaping of shells will be based on the use of already well-known surfaces, namely, surfaces of revolution, transfer, umbrella, minimal, ruled and wavy surfaces. Mainly, shell structures will be designed taking into account environmental, energy-saving requirements and transforming structures.

INFLUENCE OF THE TEMPERATURE AND HUMIDITY REGIME OF BURIED VOLUMES ON THE PRESERVATION OF ARCHITECTURAL MONUMENTS WITH MONUMENTAL PAINTINGS ON THE EXAMPLE OF THE TRANSFIGURATION CHURCH IN POLOTSK

The heat and humidity regime of the buried parts can be essential, and sometimes crucial, for the normalization of the microclimate of the entire monument. The experience of thermophysical studies in church architectural monuments shows a wide range of factors that determine the impact of the temperature and humidity regime of the buried volumes on the formation of conditions for the preservation of the monument as a whole. Currently, the Climate Laboratory of Museums and Architectural Monuments of GOSNIIR conducts research on this problem in order to create a methodology for studying and normalizing the heat and humidity regime of the aboveground and underground parts of the building as a whole to develop design and technological approaches to optimizing the conditions for the preservation of the monument. The article considers a practical example of providing heat and humidity conditions for the preservation of a monument with monumental painting.

RESISTANCE OF THE PRECAST - CAST-IN-SITU REINFORCED CONCRETE FRAMES OF CIVIL BUILDINGS UNDER SPECIAL EMERGENCY IMPACT

The paper obtained and analyzed the results of a numerical analysis of the survivability of a new industrial structural system of residential and public buildings that meets modern requirements for protection against progressive collapse, improved space-planning, architectural and thermal protection solutions. The presence of a significant number of enterprises with technological lines for the production of structures for large-panel housing construction and their market share, combined with a number of disadvantages of the applied technical and space-planning solutions, indicates the need to modernize these enterprises in order to produce products that meet modern requirements. The purpose of this study was to qualitatively and quantitatively study the parameters of the stress-strain state of the industrial structural system of civil buildings proposed by the authors with increased resistance to progressive collapse, the production of which would not require expensive modernization of the construction industry enterprises. On the basis of multi-level design schemes, an algorithm for calculating such a system for a special emergency effect is proposed. Numerical studies have established the compliance of the developed structural system with the requirements of a special limiting state under design loads and emergency effects caused by the sudden removal of a vertical load-bearing element.

REGIONAL SETTLEMENT SYSTEMS AND TERRITORIES WITH PREFERENTIAL MODES INTERACTION AND DEVELOPMENT PRINCIPLES

The presence in the newest Russian urban planning practice of special objects of professional activity - local urbanized formations is revealed. Their appearance is due to the adoption of new regulatory legal acts in various sectors of activity, significantly expanding the scope of the Urban Planning Code of the Russian Federation. They establish general requirements for the formation of territories with preferential development regimes and their subsequent use, which contain the prerequisites for significant changes in the state of territorial objects and their systems. However, to date, they are not fully used either at the stage of developing urban planning documentation, or at the stage of its implementation. Urban planning practice indicates the need to establish the relationship between the properties and characteristics of regional systems of settlements and local formations, depending on environmental factors. As a result of the analysis and systematization of modern experience in the implementation of projects for the development of local territories, the influence of the activity of their urban development on the parameters of the functioning of regional systems has been established. The revealed dependence is proposed to be used in the development of model schemes for the reorganization of regional systems, which characterize their susceptibility to the emergence of new centers of urban development. The expediency of using the developed theoretical models in the process of improving the methodology of territorial planning has been substantiated. Purposeful planning of local territories in settlement systems is presented as forecasting the emergence of new foci of development through a comprehensive assessment and consideration of the available resource potential. Thus, it ensures the regulated development of the territory. This is expressed in the achievement of the predicted parameters of changes in the state of regional settlement systems, corresponding to the conditions and requirements of their functioning. The main difference between the proposed methodology and traditional approaches lies in the simultaneous provision of the stability of the formed spatial structures and the innovation of the forms of regional systems due to the activity of local formations.

RESEARCH OF COMPLEX MODIFICATION OF HEAVY CONCRETE

Modification of the composition and structure of heavy concrete with the use of a complex chemical-mineral additive consisting of fly ash from thermal power plants, a superplasticizer, a high-valence hardening accelerator AC and a fine-dispersed clinker component is considered. Modified concrete is characterized by an increase in compressive strength at a brand age by 67%, a decrease in the water content of a concrete mixture by 13.6% and an improvement in its workability by 11-12 cm. With the combined use of a superplasticizer and a high-valence hardening accelerator AC a significant synergistic effect is observed in the format of enhancing their plasticizing effect. The high efficiency of the application of the mixed-dispersed clinker component has been established.