结构尺寸对RC柱剪扭复合受力抗震性能影响分析

Effect of structural size on seismic performances of RC columns under combined shear and torsional loadings

在地震水平作用下,曲线梁桥的桥墩、不规则钢筋混凝土(RC)框架结构的边柱、角柱等受力构件,由于上部结构的重心偏心,使构件处于剪扭复合受力状态,而产生脆性破坏,脆性破坏往往会加剧钢筋混凝土构件的尺寸效应行为。为探究剪扭荷载相互作用下钢筋混凝土柱的抗震性能和尺寸效应,建立了不同扭弯比的钢筋混凝土柱剪扭复合受力三维细观数值模型,模拟分析了扭弯比对RC柱剪扭复合受力抗震性能和尺寸效应的影响。研究结果表明:在剪扭复合荷载作用下,钢筋混凝土柱破坏更具脆性,承载能力降低;扭弯比的增大导致构件变形能力,延性能力和耗能能力下降;扭矩的存在,在一定范围内增强了钢筋混凝土柱抗剪强度的尺寸效应。对比并修正了中国规范提出的剪‐扭承载力相关方程,保证了预测结果的安全度。

Under the horizontal earthquake excitations,reinforced concrete(RC)columns such as the piers of curved girder bridge or the side columns and corner columns of the irregular reinforced concrete frame structure may be subjected to a combination of shear force and torsional moments and often produce brittle failure,due to the eccentric center of gravity of the superstructure.In addition,brittle failure often aggravates the size effect of reinforced concrete structures.In order to study the seismic performance and size effect of RC columns under combined shear and torsional loadings,a three-dimensional meso-scale numerical model of RC columns under combined shear and torsional loadings with different torsion-to-moment(T/M)ratios is established.Then,the ef‐fect of torsion-to-moment ratio on the seismic performance and size effect of RC columns subjected to shear-torsion combined load‐ing is studied.The results show that the RC column is more brittle and the bearing capacity is lower under the combined action of shear and torsion.The increase of torsion-moment ratios leads to the decrease of deformation capacity,ductility capacity and ener‐gy dissipation capacity.The size effect on shear strength of RC columns is enhanced within a certain range due to the presence of torque.The related equations of shear and torsional capacity proposed in Chinese regulation are compared and modified to ensure the safety of the predicted results.