RC圆柱受弯承载力极限值计算方法研究

运用数值计算方法对钢筋混凝土(RC)圆柱破坏时截面受弯承载力极限值进行计算,计算时考虑了箍筋对混凝土的约束效应和纵筋应力强化效应。计算结果显示截面受弯承载力极限值比规范规定的理论值有较大增加,特别是在轴压较高、箍筋约束效果明显时。截面受压区高度计算是RC圆柱截面受弯承载力计算的关键。圆柱破坏时截面受压区高度主要受轴压比、配箍特征值和纵筋配筋特征值三个参数影响。根据数值计算的结果进行回归,提出了受压区对应圆心角απ计算方法。在此基础上通过理论分析并结合95个大比例试件试验结果,提出截面受弯承载力极限值计算方法,计算结果与试验结果吻合很好。参数分析的结果表明在轴压比为0.6时截面受弯承载力极限值比规范公式计算值能提高60%左右,这一显著的弯矩强化效应值得在设计中引起重视。

CALCULATION OF THE ULTIMATE FLEXURAL CAPACITY OF NORMAL SECTION OF RC CIRCULAR COLUMNS

Numerical analysis is carried out to calculate the ultimate flexural capacity of normal section when a reinforced concrete(RC) circular column fails.The transverse reinforcement confinement and strength enhancement of longitudinal reinforcement are properly considered.It is found the calculated ultimate flexural strength is significantly larger than ideal flexural strength defined in the code,especially when the axial load ratio is high and the transverse reinforcement confinement is strong.The determination of the depth of compression zone is the key to calculate the flexural capacity of circular columns.The numerical analysis results show that the axial load ratio,transverse reinforcement characteristic value and longitudinal reinforcement characteristic value are the three main parameters which can influence the depth of compression zone.Based on the regression of the numerical analysis results,the computing formula of central angle,απ,corresponding to compression zone is established.Based on the test results of 95 larger scale columns,the formula to calculate the ultimate flexural strength is proposed,and the calculated results agree well with the test results.The results from parametric studies demonstrate that when the axial load ratio is 0.6,the ultimate flexural strength can be improved about 60% larger than that calculated from the formula provided in the code,which should be properly considered in structure design.