Bearing capacity determination of biaxially bent beams based on the design strength of reinforced concrete

Abstract

Complex deformation of reinforced concrete members is widespread in the practice of operation of many building structures. It can be caused by both force and various factors of a constructive, technological, or operational nature. The application of the concept of design strength of reinforced concrete in bearing capacity calculations of reinforced concrete members under complex deformation is complicated by the presence of additional unknown parameters: the angle of the neutral axis inclination, and various forms of the compressed concrete zone in the cross-section. The essence of the design approach is that reinforced concrete is considered a composite material that has a very specific strength characteristic - the design strength of reinforced concrete. The application of this concept creates possibilities to solve the problem of the strength of reinforced concrete members based on the classical theory of strength of materials. The implemented characteristic is an integral value that takes into account the strength and deformation characteristics of concrete, reinforcement, and its amount in the section. Based on the calculation prerequisites according to Eurocode 2, the concept of determining the value of the design strength of reinforced concrete is developed for calculating the strength of reinforced concrete beams that undergo biaxial bending. The theorem on the parallelism of the location of the planes of action of internal and external forces is applied. The calculation cases for the most expected forms of the compressed zone of concrete in a rectangular cross-section of biaxially bent beam members are considered. The values of the coefficient of influence of biaxial bending on the characteristics of the member with triangular and trapezoidal forms of the compressed zone of concrete are obtained. The developed methodology for calculating the load-bearing capacity of biaxially bent elements based on the use of design strength of reinforced concrete is brought to the engineering level of application. The proposed method of calculating the strength in the normal cross-section of beam members under biaxial bending is approved by comparing the results of calculations with experimental data for 12 samples of biaxially bent beams.