考虑剪切作用的钢筋混凝土柱抗震性能及震后残余变形研究

Considering the fact that a large number of reinforced columns, piers and piles often suffer shear failure and flexural-shear failure under seismic load, and structural design following the current code is imperfect, this research projects present the analytical results about reinforced concrete column shear-resisting mechanism, seismic performance of columns incorporating the influence of shear, structural performance control and repairability after earthquake, as well as seismic design theory incorporating the influences of shear and repair index. Reinforced concrete columns with square and round cross-sections have been tested under cyclic loading. The effects of different design parameters on the column bending, shear and slip deformations are investigated. Approaches to judging column failure patterns and predicting the load-carrying capacity and deformation of columns suffering shear-flexural failure are proposed. Based on MCFT, effective methods for predicting the restoring force model and lateral load-deformation response of RC columns subjected to shear load are developed, and the hysteretic characteristics and energy absorption capacities of columns subjected to different failure patterns are predicted. Based on the shaking table test results and the restoring force model proposed in this paper, analytical approach for predicting the residual deformation of columns under different earthquake levels is provided to examine the influence of shear on residual deformation and thus to propose effective seismic techniques and methods for reducing the residual deformation of columns, and then, the seismic design approach incorporating the maximum deformation and residual deformation of structures is developed. Research results in this research projects have contributed significantly to deepening the understanding of structural shear and flexural-shear failure mechanisms, perfecting seismic design theory and improving structural seismic safety.

针对地震中钢筋混凝土柱、桥墩、桩等受压构件大量出现的剪切、弯剪破坏现象及现行规范中结构设计不完善问题，开展钢筋混凝土柱类构件抗剪机理、剪力影响下的抗震性能、震后性能控制和可修复性以及考虑剪力和修复指标的抗震设计理论的研究。主要研究内容包括钢筋混凝土方柱和圆柱的低周反复试验，不同设计参数对柱弯曲、剪切及滑移各变形分量的影响，柱不同破坏模式的判定方法及弯剪破坏柱承载力及变形计算方法；基于修正压力场理论，建立考虑剪力作用的柱荷载-变形关系计算方法及恢复力模型，研究不同破坏模式下柱滞回特性及耗能能力；利用提出的恢复力模型及柱振动台试验结果，建立不同地震力下柱残余变形分析方法，分析剪力对残余变形的影响规律，提出减小柱地震残余变形的技术和方法；最终提出同时考虑结构最大变形和残余变形的抗震设计方法。研究成果有助于深化对结构弯剪、剪切破坏机理的认识、完善结构设计理论及提高结构抗震安全性。

研究了钢筋混凝土柱破坏模式判别、荷载-变形计算、滞回耗能分析，及单自由度体系残余变形计算等。钢筋混凝土柱静力和拟静力试验表明，地震荷载下，钢筋混凝土柱主要发生弯曲、剪切和弯剪3种形式的破坏，剪跨比较小、轴压比较大以及配箍率较小时，柱试件易发生弯剪或剪切破坏，试件的耗能能力和延性较差，表现为滞回曲线捏缩现象明显和极限位移较小；不同加载模式（单调和反复加载）对钢筋混凝土柱的破坏模式有明显的影响，与单调加载相比，反复加载下钢筋混凝土柱的抗剪承载力和刚度随变 形增加退化更明显，更易发生以剪切控制为主的破坏（弯剪破坏或剪切破坏）；钢筋混凝土柱在反复加载下因耗能和损伤累积会产生循环退化效应，导致柱的变形性能较单调加载时下降，反复加载对钢筋混凝土柱变形性能的影响在达到峰值荷载后表现非常明显，而在屈服前则无明显影响；钢筋混凝土柱在反复加载下的循环退化效应主要与加载循环次数和加载位移幅值两个因素相关，随循环加载次数的增多和位移幅值的增大趋于明显，对于加载循环次数和位移幅值相对较大的弯剪破坏柱，其极限变形（破坏变形）比单调加载时显著降低；在试验数据基础上，提出地震力作用下钢筋混凝土柱发生弯曲、弯剪及剪切破坏的概率判别方法，给出了地震作用下弯剪破坏柱恢复力模型骨架曲线的简化计算方法、考虑剪切作用影响的柱荷载–变形关系实用分析方法。提出考虑剪切作用的柱等效阻尼比计算模型，以及钢筋混凝土柱最大地震位移反应分析方法，适用于地震作用下钢筋混凝土柱抗震性能分析。基于对多条地震波作用下单自由度（SDOF）体系弹塑性地震响应（最大弹塑性变形和残余变形）的统计分析，研究了自振周期、刚度比、相对屈服力系数、峰值地面加速度及滞回模型对结构地震残余变形的影响；同时结合理论分析，建立了基于概率的钢筋混凝土柱（构件）地震残余变形计算模型。