THEORETICAL ANALYSIS OF POST-PEAK FLEXURAL BEHAVIOUR OF NORMAL-AND HIGH-STRENGTH CONCRETE BEAMS

摘要

A new method of analysing the post-peak flexural behaviour of reinforced concrete beams has been developed and applied to normal- and high-strength concrete beams. It was revealed that at the post-peak stage the neutral axis depth keeps on increasing, and at a certain point the strain in the tension reinforcement starts to decrease, even though the curvature is increasing monotonically. Such strain reversal in the tension reinforcement occurs in all concrete beams and has significant effects on the post-peak behaviour and flexural ductility of concrete beams. Therefore, the stress path dependence of the tension reinforcement needs to be taken into account in the analysis. By means of a parametric study, the variation of ultimate concrete strain with tension steel ratio and the effects of various structural parameters on flexural ductility have been studied. Based on the numerical results, design values of ultimate concrete strain that are independent of tension steel ratio have been recommended and a simple formula for predicting the flexural ductility of reinforced normal- and high-strength concrete beams has been developed.