The reliability of steel-concrete beams in the process of reconstruction

Introduction. The author solves a number of problems, including the substantiation of the required reliability level for steel-concrete beams in a reconstructed building, design parameters applicable to steel-concrete beams, use of probabilistic methods in the reliability assessment of steel-concrete beams, and reliability assessment of steel-concrete beams. Materials and methods. The engineering data, used in the reliability analysis, included steel beam examination and testing results, obtained by the Koucherenko Central Research and Development Institute of Steel Structures in 2017. The analysis was performed for the cases that took account of or failed to take account of the behaviour of a cast-in-plaсe reinforced concrete floor slab. A method of statistic simulation has proven that the probability values of snow loads set for Moscow by Construction regulations 20.13330.2016 are far below the true ones. This discrepancy reduces the reliability of the contour beams of the construction facility analyzed in this article. Results. B-12, B-45, B-49 and B-61 types of beams were used to compare the testing results with probabilistic calculations. Selected calculation results are provided in the article. An 8 mm deflection, caused by the temporary design load of 2.4 kN/m2 ensures the normal operation of a structure with a probability of 0.9973. Conclusions. A comparison between experimentally and analytically obtained deflection values has proven that the design model must have steel-concrete beams, rather than steel ones. Whenever a building structure is designed, its reliability level must be identified. The reliability of structures, having any criticality rating, depends on the values of the resistance probability in terms of their construction materials and the loads applied to them. Contour steel-concrete beams comply with the technology requirements and reliability values pre-set in the project documentation. Calculation results are validated by their convergence with the experimental data. Probabilistic methods should become a must in structural design. This measure can reduce the risk of failure or cut project costs.