新型组合碟簧自复位防屈曲支撑钢框架体系抗震性能与设计方法

Plastic deformation of both buckling-restrained braces and steel frames induces large residual deformations of buckling-restrained braced steel frames, challenging self-centering function of structures. Usually, when the axial yield force of a self-centering buckling-restrained brace, commonly formed by welding the ends of buckling restrained brace and those of self-centering system together to let them work in parallel, and that of a buckling-restrained brace are the same in design, the energy dissipation capacity of the self-centering buckling-restrained brace is deteriorated greatly because the commonly used self-centering system formed by steel strands (or fiber tendons), etc. doesn’t have nearly energy dissipation capacity. Moreover, the limited elastic deformation capacity of post-tensioned steel strands (or fiber tendons) further deteriorates the ductility and self-centering capacity of the self-centering buckling-restrained braces. When the ends are welded together, post-tensioned steel strands (or fiber tendons) induce initial stress in buckling restrained brace and it is difficult to inspect and reuse the brace. Regarding the problems above, a novel type of assembled self-centering buckling-restrained brace with disc springs in various combinations is proposed and constructed in this project. The self-centering system, formed by pre-compressed disc springs, etc., and buckling-restrained brace are assembled together by bolt connections in this new self-centering buckling-restrained brace to improve its ductility, self-centering and energy dissipation capacity and to facilitate check and reuse of the brace. By employing the disc springs in various combinations, the self-centering forces and axial deformation capacity of the self-centering system can be acquired easily by appropriately changing the ways to stack the pre-compressed disc springs. At the same time, the frictional action in the stacked disc springs can provide additional energy dissipation capacity. The working mechanism, numerical simulation models, seismic behavior and design methods of both this novel assembled self-centering buckling-restrained brace and self-centering buckling-restrained braced steel frame will be investigated by large scale cyclic loading tests and finite element method analysis. The important part research will be focus on both frictional mechanism in the stacked disc springs and the effects of the frictional mechanism on the hysteretic behavior of the self-centering buckling-restrained braces and on both the formation of self-centering buckling-restrained braced steel frame, in which the plastic deformation would concentrate mainly on the self-centering buckling-restrained braces, and the effects of the formation on the self-centering capacity of the self-centering buckling-restrained braced steel frames. This study will be helpful to further improve the seismic behavior of the buckling-restrained braced steel frames.

防屈曲支撑和钢框架的塑性变形均使支撑钢框架复位困难。当按轴向屈服承载力相同设计支撑时，常用不耗能的预拉钢绞线或纤维筋等组成的复位系统与防屈曲支撑并联后大幅降低了自复位支撑的耗能。复位系统弹性变形不足等又劣化了支撑的延性和复位能力。端部焊接并联后张拉钢绞线使防屈曲支撑产生初应力且不利于支撑检修和再利用。针对上述问题，本项目拟采用装配式组合碟簧自复位防屈曲支撑，通过螺栓并联预压碟簧复位系统和防屈曲支撑，调整碟簧组合形式获得所需的轴向复位力和变形能力，并用碟簧间的摩擦补充耗能，改善支撑的延性、耗能和复位能力，且便于检修支撑。结合试验和数值模拟，研究该种新型自复位支撑和支撑钢框架结构的工作机理、数值模型、抗震性能和设计方法。重点研究组合碟簧的摩擦机制及其对支撑滞回性能的影响规律，以及将塑性变形集中于自复位支撑的结构组成及其对复位能力的影响规律。该研究有助于进一步提高防屈曲支撑钢框架体系的抗震性能。

将防屈曲支撑和组合碟簧并联形成新型自复位防屈曲支撑（SCBRB）可用于中心支撑钢框架中来控制结构残余变形和维持震后使用功能。. 本项目对SCBRB以及该种自复位支撑钢框架结构（SCBRBF）的抗震性能进行了往复加载试验、数值模拟和理论研究。试验表明，两种构造下的SCBRB复位能力良好，其承载和耗能分别主要由自复位系统和防屈曲支撑提供，宜采用同轴组装且防屈曲支撑轴向安装长度可调的构造。与支撑端部刚接相比，销接时支撑的累积耗能更好。除钢板支撑低周疲劳受拉断裂，其他部件保持完好，有望重复利用。梁柱销接SCBRBF结构塑性发展集中于防屈曲支撑，延性和复位能力更好，即使防屈曲支撑断裂，自复位系统的完好存在仍能确保结构有较好的承载、变形能力和整体性。与之相比，刚接框架大侧移下更易发展塑性、局部屈曲和断裂，且需更高的复位比率来控制残余变形。梁柱刚接而柱脚销接时，可减小框架塑性发展和利于复位。基于试验，构建出了SCBRB和SCBRBF的合理数值模型，获得了关键构造对SCBRB和SCBRBF抗震性能的影响规律，给出了关键参数的取值范围。SCBRB的复位比率需兼顾耗能和复位能力，一般可取1/50加载侧移角下不超过1.0。此外，还可采用高强度钢材制成钢框架和在梁柱销接处增设复位装置两个措施来增强钢框架的复位能力。. 通过试验和理论分析，提出了基于力矩平衡和叠合面间相对滑动考虑组合碟簧叠合面间摩擦效应的计算公式，提出的综合考虑叠合面间以及端部碟簧与垫片间的摩擦效应的计算公式可准确预测组合碟簧轴向承载-变形关系曲线，便于设计和应用。综合10层和30层结构时程分析表明，与纯防屈曲支撑框架相比，SCBRBF的最大层间侧移不一定小，但残余侧移角更易满足1/200的限值要求。提出基于三个控制目标的设计流程和实现方法可行，可供SCBRBF结构抗震设计参考。本项目研究有助于进一步提高防屈曲支撑钢框架结构的抗震性能。

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