变截面钢管混凝土格构柱基于失效模式的抗震性能及设计控制

It is believed that there is great potential to apply variable cross-sectional Concrete-filled steel tubular (CFST) laced columns in high piers, equipment frame and large-span CFST truss arch bridges. However, seldom research has been conducted on aseismic behavior of variable cross-sectional CFST laced columns, so there is an urgent need of systemic design method.. This project is aimed at investigating the ductility mechanism，failure mode and seismic control index of variable cross-sectional CFST laced columns subjected to cyclic loading by applying numerical method and test methods. Firstly, hysteretic behaviors of variable cross-sectional CFST laced columns, including the hysteresis property，deformability ,power-wasting capacity, stiffness degradation, displacement ductility, destruction form and influence factors of the specimens will be researched by quasi-static testing, and yield sequence of members will be discussed. Then, finite-element analysis of variable cross-sectional CFST laced columns based on experiments will be performed, and the influences of parameters (including gradient of longitudinal elements, axial compression ratio, slenderness ratio of specimens, steel ratio, design strength of concrete, yield strength of steel) on the hysteretic behaviors and ductility of variable cross-sectional CFST laced columns will be investigated, so that a reasonable restoring force model will be built up, and the ductility mechanism and controlling parameters in order to insure ductility will be obtained. Failure mechanism and failure modes of variable cross-sectional CFST laced columns will be revealed, and the influence and sensitivity of parameters (internal force transfer mechanism, power-wasting capacity, development of structural deformation, locally deteriorating) on structure failure modes will be discussed by means of the FEA model. Therefore, nonlinear seismic control index of variable cross-sectional CFST laced columns can be proposed. Finally, failure evolution regulation of variable cross-sectional CFST laced columns in integral bridge structure will be studied, and the conclusions of this project will be verified on the basis of the analytical results.. The research results of this project can provide the theory basis for engineering application and seismic design control of variable cross-sectional CFST laced columns. Thus these research findings will promote technical progress of composite structure, and remarkable social and economic results will be achieved..

变截面钢管混凝土格构柱对于地震区的大跨高墩桥梁、设备构架、钢管混凝土桁拱等具有良好的适用性，其推广应用迫切需要提出系统的抗震设计方法。本项目拟以结构的延性机制、失效模式和抗震控制指标为主线开展研究，运用数值模拟和试验方法，深入研究变截面钢管混凝土格构柱的滞回特性、耗能能力、延性、刚度退化等抗震性能，探讨构件屈服顺序，建立合理的恢复力模型，提出延性机制及保证格构柱延性的控制参数；揭示变截面钢管混凝土格构柱的失效演化机理与失效模式，系统考察杆件传力机制、耗能性能、结构变形发展及局部损伤演化等对结构失效模式的影响规律和参数的灵敏度，提出抗震控制指标；最后深入分析变截面钢管混凝土格构柱在整体桥梁工程中的地震失效演化规律，对本项目的研究结论进行验证。研究成果可为变截面钢管混凝土格构柱的工程应用和抗震设计控制提供理论依据和指导，对推动钢管混凝土组合结构的技术进步有积极贡献，具有良好的经济和社会效益。

本项目以四肢变截面钢管混凝土格构柱为研究对象，深入研究该新型组合柱的滞回特性、耗能能力、延性、刚度退化等抗震性能，建立合理的恢复力模型，系统分析钢管混凝土格构式高墩连续梁桥的弹塑性抗震性能，提出抗震设计简化方法。.在格构柱抗震性能试验研究方面，本项目以缀管布置形式和柱肢坡度为试验参数，进行了7根四肢变截面钢管混凝土格构柱（包括6根斜缀管式格构柱和1根平缀管式格构柱）的拟静力试验，分析试件的滞回曲线、骨架曲线、延性、能量消耗、强度退化、刚度退化、变形恢复等方面的受力性能和规律，探讨了试件的破坏模式。.在格构柱抗震性能理论研究方面，本项目应用通用程序OpenSEES，建立四肢变截面钢管混凝土格构柱分析模型，在试验结果验证基础上，拓展分析了柱肢坡度、轴压比、构件长细比、支主管面积比、斜缀管布置形式、柱肢钢材强度、缀管钢材强度、混凝土强度等参数对四肢变截面钢管混凝土格构柱抗震性能的影响，建立钢管混凝土格构柱延性机制。在有限元参数分析的基础上，借鉴等截面钢管混凝土格构柱骨架曲线统一算法的计算框架，采用等效长度法，拟合得到四肢变截面钢管混凝土格构柱骨架曲线各特征值（弹性刚度、水平峰值荷载、峰值荷载位移、下降段刚度）及恢复力模型的计算公式，并得到工程实例的验证。最后给出四肢等截面和变截面钢管混凝土格构柱恢复力模型合理实用的计算方法。.在钢管混凝土格构柱抗震性能研究基础上，以四川省干海子大桥为工程背景，对钢管混凝土格构式高墩连续梁桥的动力性能和抗震设计方法进行深入探讨。研究地震作用下该类桥梁的动力特性和不同设计参数的抗震适用性，建立抗震优化设计准则，并提出基于周期的钢管混凝土格构式高墩连续梁桥抗震设计简化方法。合理简化设计过程，有效改善结构内力分布，提高抗震性能，解决了该类工程应用缺乏系统的抗震设计理论的技术难题。.本项目研究成果丰富，发表12篇学术论文，多人次参加国内学术会议，培养了2名硕士研究生。本项目在钢管混凝土格构柱的抗震试验研究与计算理论分析方面都具有明显的创新性，研究成果可为钢管混凝土组合结构的工程应用提供理论支撑，为该类结构的抗震设计规程提供借鉴和参考，为结构优化设计和提高结构安全性作出积极贡献。