On the cracking behaviour of the reinforced concrete tension chord under repeated loading

摘要

It is well known that repeated loads lead to increasing crack widths and deformations of reinforced concrete members. This is due to the progressive reduction of the parameters influencing the bond mechanism at the steel-concrete interface. However, current engineering methods employ severe simplifications to account for this influence, in particular to estimate values under permanent load. In this paper a model is presented to reproduce the distribution of longitudinal stresses and strains, bond stresses and relative slips along the crack spacing of a reinforced concrete tie with number of cycles. The model allows for a better understanding of the mechanical degradation sources affecting the evolution of tension-stiffening contribution. On the one hand, a cyclic degradation law is introduced to affect the local bond-slip behaviour. On the other hand, the mechanical damage of concrete is also introduced in the analysis. A parametric study is reported to show the role played by the different sources of degradation. Finally, the model capabilities are employed to analyse own experimental results.