Statistical models for predicting the reliability and bearing capacity of normal sections of prestressed reinforced concrete beams

Abstract

Effective regulation of the material consumption of buildings and structures and their safe operation are possible only with a precise assessment of the reliability and bearing capacity indices of building elements.

Ukrainian and European standards allow the design of prestressed reinforced concrete beams with a sufficient level of bearing capacity, confirmed by many years of engineering practice. However, the actual reliability level of such elements at the design stage is unknown. In some cases, it turns out to be overestimated and causes an overrun of materials. Also, it can be, on the contrary, insufficient, which leads to additional costs for eliminating the consequences of failures during operation. The main problem in using the reliability theory for the design of reinforced concrete structures is the need to accumulate a large amount of statistical data and the complexity of computational work. Therefore, it is necessary to develop a simpler reliability assessment apparatus for practical use.

The authors of the article carried out a large number of numerical experiments. As a result of these experiments, adequate statistical models of the design reliability and bearing capacity of normal sections of prestressed reinforced concrete rectangular beams have been obtained. The main advantage of these models is that they allow the designer to explore both the direction of the change in the bearing capacity and the reliability index with the change in the initial design factors - the concrete class, the class of bar reinforcement, the class of wire reinforcement, and the reinforcement ratio.

It has been established that the influence of specified design factors on the design reliability indices and the design bearing capacity of beam structures with a rectangular section is mainly of a multidirectional nature. In this case, it is necessary to search for compromise solutions that comprehensively take into account all the parameters and are achieved through mutual concessions in "conflict" situations.