不锈钢结构高强度螺栓端板连接节点的抗震性能与设计方法研究

Stainless steel structures have wide-range application potentials in civil and industrial structures, particularly in highly corrosive environment. Existing research studies have investigated the mechanical behaviors of structural members with consideration of apparent non-linear hardening properties of the material. However, studies about the seismic performance of stainless steel joints and structures incorporating apparent non-linear material hardening effect are rare while they are critical and necessary for any application in seismically hazardous regions of China. This project focuses on the high strength bolted end-plate joints, which is the one of the commonly used beam-column joints in stainless steel frame structures. High strength bolts, as one key component for joints will be investigated from the perspectives of mechanical performance, pre-load level and the fastening technique. The stainless steel plate with high slip coefficient will be developed. Experimental studies about seismic performance of the joints will be then performed assisted with the refined finite element modelling to derive representative factors for performance assessment and to evaluate the effect of material non-linear hardening properties and stainless steel high strength bolts on joint performance. The proper joint failure sequences and the mechanism of energy dissipation will be determined. A modified Pinching4 hysteresis model will be proposed to characterize the two-stage mechanical behavior of joints. Finally, seismic design schemes and proper configuration measures for joints will be developed. The achievements of this project will provide technical proof for improving the existing stainless steel design specification.

不锈钢结构在腐蚀性环境下的工业与民用建筑中具有广阔的应用前景。国内外相关研究已经揭示了不锈钢材料显著非线性强化的特征及其对构件受力性能的影响，然而在其对节点及结构抗震性能的影响方面研究较少，阻碍了不锈钢结构在我国抗震设防区的应用。本项目针对不锈钢框架结构中典型梁柱节点-高强度螺栓端板连接节点的抗震性能进行研究，以节点关键部件（高强度螺栓和摩擦面）的研究为切入点，建立不锈钢高强度螺栓的力学性能、预紧力及施拧方案，研发不锈钢高抗滑移系数摩擦面，进而开展节点的抗震性能试验研究和精细化有限元模拟，获得表征节点抗震性能的关键参数，揭示不锈钢材料显著非线性强化及不锈钢高强度螺栓对节点抗震性能的影响，确定节点各部件的合理破坏顺序和耗能机制，建立符合节点“两阶段”受力特征的改进Pinching4滞回模型，最后提出节点抗震设计方法和构造措施。本项目的研究成果将为完善我国相关设计规范提供重要参考。

不锈钢结构具有优异的耐腐蚀性和良好的力学性能，是实现强腐蚀环境下结构高安全性和长耐久性的重要解决方案。目前国内外对不锈钢结构材料和构件层面开展了大量研究，节点方面研究较少，缺少配套的高强度螺栓和高抗滑移系数摩擦面等关键连接件。本项目围绕不锈钢高强度螺栓外伸端板连接点开展了系统的研究。首先，针对节点关键部件中高强度螺栓缺失问题，采用国产沉淀硬化型不锈钢S51740研发了10.9级不锈钢高强度螺栓，并采用MoS2基润滑剂，攻克了不锈钢螺栓拧紧过程的咬死问题，建立了不锈钢高强度螺栓的施拧工艺；然后，针对常规喷砂、抛丸等工艺下，不锈钢板的抗滑移系数低的问题（小于0.20），提出了拉丝、刻痕、喷涂不锈钢粉末和抗滑移漆等不锈钢表面处理工艺，将不锈钢板表面的抗滑移系数提高到0.60，并揭示了表面粗糙度与抗滑移系数的正比例关系；进而，开展了12个不锈钢外伸端连接梁柱节点的拟静力试验，获得了节点的破坏模式、滞回曲线、骨架曲线、延性系数和耗能系数等抗震性能关键指标，揭示了不同几何构型、节点各部件和梁承载力匹配关系下节点的破坏模式和耗能机理；最后，提出了5参数的Ramberg-Osgood型全过程弯矩-转角模型，并基于“整体组件法+局部拟合法”基本思路，克服了撬力计算的难题，建立了模型关键参数的计算公式。与试验数据和有限元分析结果对比表明，项目提出的弯矩-转角曲线具有较好的精度。本项目研究成果为我国相关规范的修订和工程实践提供理论依据和参考。