Numerical analysis of reinforced concrete continuous deep beams

Abstract

The structural behaviour of deep beams is still not completely understood, since, for example, plane sections do not remain plane and no uniform shear flow can develop because of the small ratio between depth and shear span. If in addition, the supporting system is also statically indeterminate, the number of difficulties increases. In order to investigate the behaviour of statically indeterminate deep beams, a series of fourteen tests has been carried out. Variables were the slenderness, the ratio between top and bottom reinforcement, and the amount of shear reinforcement. Complementary to these experiments numerical simulations have been carried out. This paper focuses on the computational aspects. A good match between experimental behaviour and numerical simulation was found over the entire range, which increases the confidence in the predictive capacity of non-linear finite element analysis. Extrapolation was the next step: calculations were made for cases in which either a material or a structural parameter was varied beyond the tested range. For this study, the amount of compressive strength reduction by transverse tension was chosen as a material parameter. In general this appeared to have a negligible effect on the behaviour. Only in the case of large reductions, however, a change in failure mechanism and a decrease in failure load were found. The orientation and the am()unt of web reinforcement was chosen as a structural parameter. Compared to the original calculation with vertical reinforcement only, a decrease in failure load is found when only horizontal web reinforcement was present. A combination of both horizontal and vertical l'einforcemen! proved to be the most effective: at the expense of more reinforcement, it resulted in a strength increase as well as in small crack widths.