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The features of the behavior of steel-plate composite walls for static short-term loads are considered. Based on the analysis of modern technical and regulatory documentation, the rationale for the chosen research topic is given. A review of the literature is performed, and the features of development are noted. Description and features of the experimental structures are presented. Analytical and numerical calculations of structures for central compression have been performed. A description of the calculation complex is presented; a description of numerical models, features of their construction and calculation are given. Calculation results are presented – features of changes in structural rigidity during load application. The general types of experimental models tested for central compression are presented, and the destruction pattern is shown. The analysis of the experimental data obtained and their comparison with analytical and numerical calculations are performed. An assessment of the features of modeling steel-plate composite structures in software complexes is given.

Рассмотрены нормы по расчету сжатых сталежелезобетонных стоек, а также экспериментально-теоретические исследования других авторов. Выполнено экспериментальное исследование работы сжатых стоек с малым эксцентриситетом на диапазоне гибкостей от 6 до 20. Выполнено численное моделирование различных вариантов конструкций: с бетонами от В30 (С25/30) до В100 (С90/105), с сердечником в виде двутавра, с сердечником в виде квадрата. Полученные данные экспериментов и расчетов сопоставлены с теоретическими кривыми коэффициента продольного изгиба. Установлено, что кривые коэффициента в СП 266.1325800 и Eurocode 4 имеют не корректную форму и не отражают действительной работы сталежелезобетонных сжатых элементов. Использование кривой СП 266.1325800, основанной на кривой для железобетонных конструкций, а также кривых Eurocode 4, которые приняты как для стальных сечений (по Eurocode 3) – не дает нормального запаса конструкций и не обеспечивает надежность. Оба норматива игнорируют различный характер работы бетонов обычной и высокой прочности. В результате исследований установлено, что класс прочности бетона на сжатие влияет на устойчивость стержней с гибкостью от 6 до 10, при этом влияния формы поперечного сечения сердечника (вида жесткого армирования) практически нет. Для гибкостей от 10 до 20 может быть принята единая для всех бетонов кривая коэффициента. Разработаны кривые коэффициента для расчета сжатых элементов при малых эксцентриситетах и кратковременном действии нагрузок; предложена формула расчета несущей способности сжатых стоек.

The features of the behavior of steel-plate composite walls for static loads are considered. Based on the analysis of modern technical and regulatory documentation, the rationale for the chosen research topic is given. A review of the literature is performed, and the features of development are noted. A detailed description and features of the experimental structures under study and the materials used are presented. The features of the test are considered, and the test equipment is described. Analytical and numerical calculations of structures for eccentric compression have been performed. The description of the calculation complex and the used models of materials is presented; the description of numerical models, the features of their construction and calculation are given, the results of calculations are presented – stress distributions, deformations, features of cracking. The general types of experimental eccentric compression wall models are presented, the nature of the loss of bearing capacity of experimental structures is described, and a picture of destruction is presented. The analysis of the experimental data obtained and their comparison with analytical and numerical calculations are performed.

Stability calculation of steel rods should consider residual stresses, as well as local imperfections (bends, buckling). Codes of EU, USA, PCR considering difference between welded and rolled I-beams on compression and compression with bending. Coefficient of longitudinal bending has values that consider the presence of different values of residual stresses for welded and rolled I-beams. Russian code for the design of steel structures (SP 16.13330) for conditionally centrally compressed rods does not distinguish between methods of I-beams production. To determine residual stresses, a wide range of Russian profiles with different thin-walled was studied. Residual stresses for small-sized profiles were carried out by partitioning, for large I-beams - by drilling blind holes. The actual values of residual stresses in flanges and walls are established; most suitable curves for their approximation are selected. The actual shape of I-beams was also measured with a laser scanner. According to the results of curvature measuring, the limit and average values of local flanges deflection are established. Considering experimental studies, FE-modeling of rods with residual stresses was performed for both rolled and welded I-beams. In addition to code eccentricities, local shape imperfections were modeled. It is established that rolled I-beams show higher values of critical forces than welded ones by 8-16%. This is true for steels C355 and C390 with a lambda-factor of more than 4, and for C255 with lambda-factor more than 3. According to the study, a coefficient is proposed that increases the bearing capacity of rolled I-beams for medium and large flexibilities.

A brief review of actual methods of calculation of the shear forces is performed; the calculated dependences are analyzed and their estimation is given. The shortcomings of the methods are noted, the main one is the empirical approach to the solution of the problem. The features of destruction of reinforced concrete elements along an inclined section are considered; the mechanism of destruction, on which the actual normative documents are based, is analyzed. A method of design of reinforced concrete elements under the action of shear forces is proposed. The method is developed on the basis of analysis of the stress-strain state of the support zone of a reinforced concrete beam of rectangular cross-section. In the design work, two stages are distinguished. This made it possible to avoid empirical coefficients in the equations. A numerical model was created. Stress distribution in the beam was obtained and analyzed. Conclusions about the actual stress distribution in the compressed zone of concrete above the top of the inclined crack and the actual compressive strength of concrete are made. The proposed design method made it possible to describe the process of destruction of the inclined section in strict accordance with the experimental data. The proposed approach allows to obtain accurate results not only for reinforced concrete elements of simple cross-section (rectangular, T-section), but also for other shapes of sections of a more complex configuration.