科研之友
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摘要
Buckling of longitudinal bars is a common failure mode in reinforced concrete columns under earthquake, and can lead to the deterioration of structural seismic performance. In this study, a numerical method for predicting the average behaviour of reinforcing bars in compression considering the influences of buckling is developed. The bare reinforcing bar is divided into several segments, and a set of differential equations is established, in which both the material and geometrical non-linearities are taken into account. Then, a set of non-linear equations is derived by solving these differential equations and combining the conditions of geometrical compatibility and mechanical equilibrium so that the uniaxial compression stress-strain relations of buckling bars can be calculated numerically. The developed numerical method is verified against experimental data. The results of simulation and test are analysed; it is found that, unlike the case of elastic buckling, buckling of the reinforcing bars with commonly used bar length-to-diameter ratio usually occurs in the post-yield stage, and the degradation of post-buckling stress is mainly affected by the bar length-to-diameter ratio, the yield strength and the ultimate strength-to-yield strength ratio. Finally, a pseudo-material stress-strain relationship of a reinforcing bar in compression considering the effects of buckling is established by performing parametric analysis.
