No abstract

Although after cracking, concrete has negligible tension capacity, the intact concrete between cracks within the tension zone of a reinforced concrete beam can still develop significant tensile stresses to contribute to the flexural stiffness of the concrete beam. Such a tension stiffening effect in a flexural member is not quite the same as that in an axial member because the tensile stresses in a cracked flexural member are induced not only by the steel reinforcement-concrete bond but also by the curvature of the flexural member. In this study, the tensile stresses developed in cracked concrete beams are analysed using a finite-element (FE) model that takes into account the non-linear biaxial behaviour of the concrete and the non-linear bond stress-slip behaviour of the steel reinforcement-concrete interface. Based on the numerical results so obtained, a tensile stress block is proposed for section analysis of the momentcurvature curves of reinforced concrete beams at both the uncracked and cracked states. It will be shown in part 2 of this paper that the tensile stress block may also be used for member analysis of the load-deflection curves of concrete beams without resorting to FE analysis.

No abstract

Based on finite-element analysis of cracked reinforced concrete beams, a tensile stress block was proposed in part 1 of this paper. Here, the proposed tensile stress block is contrasted with existing ones developed by others to provide an overall review. The proposed tensile stress block is then applied to a section analysis of beams to evaluate the moment-curvature curves of typical beam sections. The section analysis results are compared with available experimental results and empirical curves given in design codes to demonstrate the validity of the tensile stress block. Subsequently, the proposed tensile stress block is applied to member analysis by first dividing the beam member into short segments and then applying section analysis to each segment to evaluate the loaddeflection curves of typical beam members. The member analysis results are checked against finite-element analysis results and available experimental results to fine-tune the tensile stress block and verify the accuracy of the finetuned tensile stress block. Such member analysis could be extended to multi-level analysis of frame structures for their full-range load-deflection behaviour at the elastic, post-crack and post-peak states.