锈蚀H型钢梁柱焊接节点地震损伤机理与破坏准则研究

As an important part of steel structures, beam-column welded joints may suffer from both corrosion and earthquake during the whole life cycle. Corrosion increases the local stress level, reduces the plasticity and fracture toughness of steel, accelerates the crack initiation and buckling development, and is bound to have a significant impact on the seismic performance of the beam-column welded joints. This project takes the corroded H-steel beam-column welded joints as the research object and is aimed at realizing its seismic damage evaluation and prediction. Through the combination of theoretical analysis, experimental research and numerical simulation, this project will systematically research the seismic damage mechanism and failure criterion of corroded beam-column welded joints. Through the measurement and analysis of the mesoscopic characteristics of base metal/weld area of the corroded joints, the corrosion degree evaluation method and morphological characterization model will be proposed. By researching the cyclic damage accumulation and fracture mechanism of corroded steel at base metal/weld area, the cyclic constitutive model and meso-fracture model will be proposed. Then, the hysteretic behavior and failure characteristics of corroded beam-column welded joints under low-cycle reciprocating loads are studied to reveal its seismic damage mechanism. The simplified method of equivalently considering the buckling behavior of plastic hinge zone of corroded joints in the material constitutive are explored, then the damage criterion of buckling and fracture and the damage index calculation model for corroded joints will be proposed based on the material constitutive, and employed to construct the seismic failure criterion of corroded beam-column welded joints. The research results will provide theoretical basis and technical support for the seismic performance evaluation of existing steel structures in corrosive environments.

梁柱焊接节点作为钢结构重要组成部分，在全生命周期内可能同时遭受锈蚀与地震双重威胁。锈蚀提高了钢材局部应力水平，降低钢材塑性与断裂韧性，加快裂纹萌生和屈曲发展，势必对梁柱焊接节点抗震性能产生显著影响。本项目以锈蚀H型钢梁柱焊接节点为研究对象，以实现其地震损伤破坏评价和预测为目标，围绕其地震损伤机理与破坏准则展开研究。采用理论分析、试验研究与数值模拟相结合的方法，研究节点母材及焊接区锈蚀表面细观特征，提出腐蚀程度评定与形貌表征方法；研究母材及焊接区锈蚀钢材循环损伤累积与断裂机理，提出其循环本构与细观断裂模型；研究低周往复荷载作用下锈蚀H型梁柱焊接节点滞回性能与破坏特征，揭示其地震损伤破坏机理；提出节点塑性铰区考虑屈曲及锈蚀影响的等效本构模型，建立基于材料本构的断裂屈曲损伤判据及锈蚀节点损伤指数计算模型，构建锈蚀H型梁柱焊接节点地震破坏准则，为既有锈蚀钢结构抗震性能评估提供理论依据和技术支撑。

本项目以锈蚀H型钢梁柱焊接节点为研究对象，围绕其地震损伤机理与破坏准则展开研究。利用三维非接触式形貌仪对锈蚀钢材/焊缝连接进行了表面形貌测试，揭示了其表面细观特征差异性及锈蚀深度、锈坑三维参数概率分布特征与时变规律，提出了锈蚀钢材/焊缝连接锈蚀评价参数体系与形貌表征方法。开展了锈蚀钢材/焊缝连接单调拉伸与低周往复荷载试验，研究了锈蚀钢材/焊缝连接单调拉伸与循环加载力学性能与破坏特征，揭示了其力学性能退化规律与细观断裂机制，建立了锈蚀钢材/焊缝连接循环本构模型与细观断裂模型。开展了加速锈蚀H型钢梁柱焊接节点低周往复荷载试验，研究了锈蚀对节点抗震性能包括承载力、刚度、变形性能、耗能能力及破坏特征的影响；结合有限元数值模拟方法与参数分析，揭示了锈蚀梁柱焊接节点抗震性能控制因素与损伤破坏机理。开展了节点塑性铰区带锈坑四边简支板和三边简支板单调受压和循环受压有限元数值模拟，研究了锈蚀特征、板件尺寸对板件单调受压力学性能、循环受压曲线的影响规律，揭示了锈蚀板件屈曲控制因素、受压屈曲路径及损伤退化准则，提出了塑性铰区锈蚀板件屈曲等效本构模型。建立了能够同时模拟断裂与屈曲损伤破坏行为的锈蚀H型钢梁柱焊接节点“焊接区—塑性铰区”实体—杆单元多尺度模型，提出了锈蚀H型钢梁柱焊机节点断裂屈曲损伤判据，建立了锈蚀H型钢梁柱焊接节点破坏准则。同时，在项目计划外开展了加速锈蚀H型钢柱低周往复荷载试验与有限元数值分析，揭示了锈蚀钢柱抗震性能控制因素与损伤退化机理。基于提出的锈蚀钢材循环本构模型及塑性区锈蚀板件屈曲等效本构模型，将断裂与屈曲两种不同层次的失效行为统一至材料层次，建立了锈损钢框架抗震性能评估方法。本项目进一步拓宽了既有钢结构耐久性与安全性研究的范畴，丰富了既有锈损钢结构抗震性能研究的内容，为既有锈损钢结构抗震性能评估、维修与加固决策提供依据。