压弯剪扭复合受力下加固RC震损柱二次地震破坏机理研究

In order to ensure the resistance of damaged structures after strengthening under severe earthquake, the safety and reliability of their vital supporting members must be fully safeguarded, and the key of the research should be focused on choosing right physical quantities to describe the structures' damage caused by earthquake. So the seismic behavior of the strengthened structures must be investigated, which are under combined action of compression-bending-shear-torsion and damaged before strengthening. The low-cycle fatigue testing was conducted to investigate the seismic performance of the damaged RC columns strengthened with high performance ferrocement laminate and bonded steel plates under combined action of compression-bending-shear-torsion. The influence of initial seismic damage, durable injury, and coupling effect between them on the aseismatic performance were mainly discussed. At the same time, numerical analysis was conducted to investigate other factors affecting the seismic performance of strengthened columns. Based on experimental research and theoretical analysis, index of the effect of initial damages and combined action on the aseismatic performance of the strengthened members was proposed, as well as the seismic failure criteria and multi-linear hysteretic model of the strengthened members. On the basis of the existing weighted combination model of component's damage index, overall damage model and storey damage model of the strengthened structure were proposed with weighted coefficient method. The models proposed were added into the damage class of OpenSees. And then, the program was used to evaluate the seismic damage performance of the strengthened structures, so that its feasibility could be verified. The results provides theoretical basis for seismic performance evaluation of strengthened damaged structures, strengthening design method based on seismic damage performance, and investigation of collapse-resistant capacity.

确保强震作用下损伤结构加固后的抗震能力，根源在于保证竖向传力构件的安全可靠，研究关键在于选择正确的物理量来表征地震引起的结构破坏，因此必须对实际处于压弯剪扭复合受力状态的损伤构件进行抗震加固研究。项目拟采用加筋高性能砂浆-粘钢联合加固震损钢筋混凝土柱，进行压弯剪扭复合受力下的低周疲劳荷载试验，着重分析首次地震损伤、耐久性损伤及二者耦合效应对加固柱抗震性能的影响；同时对影响加固柱抗震性能的其它因素进行数值分析；在此基础上建立复合受力、已有损伤等对加固构件性能的影响指标；提出加固柱抗震破坏准则和多线型恢复力模型；在已有构件损伤指标加权组合模型基础上，采用权重系数法建立加固结构层损伤模型和整体损伤模型；对OpenSees进行二次开发，将所建模型加入源程序，通过某加固结构的地震损伤性能评估验证程序的可行性。课题的完成将为震损结构加固后的抗震性能评估、基于损伤性能的加固设计和抗倒塌分析提供理论基础。

钢筋混凝土柱作为混凝土结构中最基本、最重要的竖向传力构件，起着传递各类荷载至基础的重要作用。实际承受压弯剪扭复合作用的在役柱一旦发生破坏，轻则导致结构承载力下降，重则导致结构失稳，甚至坍塌。因此复合受力情况下损伤RC柱的加固性能及破坏机理研究尤为重要。本项目以笔者提出的新型加固方法—“加筋高性能砂浆（HPFL）-粘钢联合加固技术”为基础，对损伤RC柱加固后在复合受力情况下的抗震破坏机理进行研究。首先，基于课题组已完成的粘结强度试验，建立HPFL加固层与混凝土粘结强度预测的BP神经网络模型。其次，进行8根RC柱轴压性能试验研究和偏压性能有限元分析；柱加固后极限承载力得到显著提高，变形能力增强；粘贴角钢时加固箍筋强度折减系数取0.55，若无粘贴角钢并对构件进行适当倒角时可取0.72，倒角直径大于边长1/3时，可按圆形截面取1.0；钢板表面砂浆的承压有效利用系数取0.7，其余部分取0.3；提出了加固柱轴压、偏压承载力计算方法。最后，进行25根弯剪扭复合受力下的损伤加固RC柱抗震性能研究和数值分析，试验测试共分4根未加固的对比柱、5根完好加固柱、7根震损加固柱、5根锈蚀加固柱和4根震损锈蚀耦合损伤加固柱五组，每组受力方式分为单向压弯剪、单向压弯剪扭、双向压弯剪和双向压弯剪扭四种，地震损伤程度分为屈服、最大荷载和破坏三类，锈蚀柱纵筋腐蚀率为2.67%、箍筋腐蚀率为15.94%。研究表明不同加载方式下，加固柱承载力均得到了显著提高，提高幅度在29.9%~127.0%之间，且随轴压比增大，承载力提高。在本文所考虑的扭转和偏压范围内，影响加固构件承载力、刚度和耗能的主要因素是扭转和大偏心受压。根据偏心受压、扭转以及损伤对承载力、刚度和耗能的影响，定义了扭转影响系数dt，偏压影响系数de和初始损伤系数di，并给出了对应计算方程和相关参数的取值。以Park-Ang双参数破坏准则和陈林之双参数破坏准则为基础，考虑扭转、偏压和初始损伤的影响，建立了对应的修正破坏准则、层损伤模型和整体损伤模型。依据试验结果建立了构件恢复力模型，推导并验证了压弯剪扭复合受力承载力计算统一公式。通过本项目的研究，揭示了损伤加固结构在压弯剪扭复合作用下的抗震性能和破坏机理，为震损结构加固后的抗震性能评估、基于损伤性能的加固设计和抗倒塌分析提供了理论基础，并对该加固技术的推广应用起到良好的促进作用。