The article proposes a solution to the problem of more accurately taking into account the influence of scale factors on the qualitative and quantitative indicators of the stress-strain state obtained by testing both individual structures and structural systems made of reinforced concrete. Methodical approaches to modeling tests for static and dynamic loads are considered, with the aim of taking into account the scale effects that occur during the manufacture of prototypes of models of individual structures and structural systems made of reinforced concrete. Comparative analysis estimated effect of different geometric proportions for free opera statically determinate beams and for a fragment of a monolithic reinforced concrete frame multistory buildings, experimental studies which were performed by the authors earlier. Analytical patterns were established to assess the impact of large-scale factors on the particular static and dynamic deformation of structures and structural systems of reinforced concrete. The results can be taken into account when conducting experimental studies of model reinforced concrete structures for dynamic emergency loads
Currently, the issue of increasing the efficiency of the use of traditional materials in building structures due to rational structural solutions and improving design methods and material models is relevant. The use of indirect reinforcement improves the strength and deformation characteristics of concrete. The article considers the influence of indirect reinforcement in the form of transverse welded meshes on the strength and ultimate compressibility of concrete. The main attention is paid to the determination of the strain values determining the stress-strain diagram for concrete with indirect reinforcement. It is known that with an increase in the strength of concrete, the value of its ultimate compressive strains decreases. Indirect reinforcement can significantly increase the ultimate compressibility of concrete and makes the difference in ultimate deformations even more significant for concrete of different strengths. In this context, when calculating structures in accordance with the limit state design and decreasing the strength values of concrete in order to obtain the necessary security, it is possible to overestimate the ultimate compressibility of concrete. This is unacceptable in calculations based on the deformation model, since the achievement of ultimate deformations of the material is the main criterion for structural failure. To confirm the hypothesis, the results of tests for central compression of concrete with indirect reinforcement in the form of transverse welded meshes were selected. The strain values at the peak of the diagram were calculated for the experimental samples. Calculations were also performed for the characteristic compressive strength values and the design values of strength. The results are compared with experimental data. A significant overestimation of the values of strain at the peak of the diagram was noted in the calculations based on the characteristic compressive strength values and the design values of strength.
The article examines the role of dynamic collapse modelling for reinforced concrete structures exposed to emergency dynamic loads. The authors reviewed methodological approaches to test simulation of emergency loads applied to reinforced concrete structures with the aim to consider the scale effects revealed in manufacturing of test models of reinforced concrete structures. The comparative analysis is based on the examples of the authors’ previous computational and experimental investigations of the reinforced concrete building frames made of cast-in-situ reinforced concrete. The article determines regularities in the impact of physical and geometric similarities applicable to models and full-scale specimens. The obtained results can become a base for a mathematical description of the impact produced by scale effects that shall be considered in simulation of emergency dynamic loads for the given structures.
In recent years, numerous experimental and especially numerical studies have been conducted in order to study the mechanisms of the resistance of reinforced concrete building frames to progressive collapse during the instantaneous removal of one of the columns. Analysis of these researches shows that almost all study deals with strength performance of RC structural elements under quasi static or instantaneous loss of column. At the same time, a number of numerical and analytical studies of the progressive collapse behaviour of steel moment frames as well as fragments of RC moment frames indicates that loss of bearing capacity of structures can be associated with buckling behaviour. Therefore, using the theory of functional similarity, a physical model of the reinforced concrete frame of a multi-storey building and a methodology for experimental studies of the buckling and fracture of this structural system under instantaneous loss of the corner column are proposed.
The paper considers a new industrial constructive 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 share in the market, combined with a number of shortcomings of the technical and space-planning solutions used, indicate the need to modernize these enterprises for their production to meet modern requirements. The purpose of this study was to develop an industrial constructive system of civilian buildings with increased resistance to progressive collapse, the production of which would not require expensive modernization of the construction industry enterprises. Based on the level calculation schemes, an algorithm is proposed for calculating such a system for a particular emergency impact. Numerical studies have established the correspondence of the developed constructive system to the requirements of a special limiting state under design loads and accidental effects caused by the disconnection of the vertical bearing from work.
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