带延性铸造件支撑的特殊中心支撑钢框架体系抗震性能研究

Replacing gusset plates and HSS(Hollow Structural Section) in special concentrically braced frames (SCBFs) with Cast Modular Ductile Braces (CMDB) and double-tube buckling restrained braces respectively, and forming the special concentrically braced frames (SCBFs) with Cast Modular Ductile Braces (CMDB). The CMDB system introduces cast components at the ends of the HSS in an attempt to produce a system with reliable strength, stiffness, and deformation capacity. A cruciform cross-section has been chosen for the cast component geometry, which is specially detailed to enhance energy dissipation and increase low cycle fatigue life thereby reducing the likelihood of fracture. At the same time the buckling-restrained braces also has been introduced as an alternative to the brace of SCBFs in order to prevent buckling, and post-buckling of Hollow Structural Section(HSS). Due to the buckling-restrained braces the inelastic deformation capacity of the CMDB system is given full play, and under severer earthquake the buckling-restrained braces can supplementally dissipate energy to enhance the seismic performance of the structure. Very limited research on the design of SCBFs with Cast Modular Ductile Braces has been completed to date abroad, but there is a lack of domestic research on the issue to date..The seismic performances of SCBFs with Cast Modular Ductile Braces will be studied in the project through experimental study, numerical simulation and theoretical analysis. The forced mechanism and the restoring force model of CMDB, and the horizontal resist lateral stiffness, capacity of energy dissipation, ductility and the collapse mechanism of the new structure will be obtained. In addition, finite element models of the Cast Modular Ductile Braces and its corresponding structure will be developed. the rule of parameter influence，the collapse criterion and performance evaluation index will be obtained. At last, the design method and seismic fortification measures will be provided based on structural behavior. The research work has both theoretical significance and extensive application prospect.

带延性铸造件的支撑是将特殊中心支撑钢框架（SCBFs）中连接支撑的节点板和支撑分别用延性铸造件和双钢管防屈曲支撑替换，形成带延性铸造件支撑的SCBFs体系。通过铸造件的几何形状来发挥支撑的非弹性变形能力，缓解梁柱节点区域的应力集中，提高体系的抗震性能与低周疲劳寿命。目前，带延性铸造件支撑的SCBFs体系抗震性能的相关研究很少见诸文献。.项目以带延性铸造件支撑的SCBFs为研究对象，采用试验研究、数值模拟和理论分析相结合的方法对其抗震性能进行研究，得到带延性铸造件支撑的受力机理及恢复力模型，分析新型体系的极限承载力、水平抗侧刚度、耗能能力与延性、倒塌模式等抗震性能，建立该新支撑与相应结构体系的有限元分析模型，系统分析设计参数的影响规律，得出体系的层间倒塌判别准则和性能评价指标，基于结构性态提出新体系的设计方法和抗震构造措施。研究成果将为该类工程应用奠定理论基础，具有重大的理论意义和应用价值。

特殊中心支撑钢框架结构体系（SCBFs）当前的设计方法因焊接节点板的焊缝被撕裂、支撑发生局部屈曲等问题阻碍了支撑构件作用的充分发挥。带延性铸造件的支撑是将SCBFs中连接支撑的节点板和支撑分别用延性铸造件和双钢管防屈曲支撑替换，形成带延性铸造件支撑的SCBFs体系，支撑连接和支撑耗能控制设计是关键。为研究带延性铸造件支撑的SCBFs结构的性能，项目完成了31个带延性铸造件的防屈曲约束支撑构件试验和72个有限元模型分析；完成了7榀带延性铸造件支撑的SCBFs结构的1/3缩尺试验和65个有限元模型分析。发现所有支撑展示了较好的耗能性能和力学性能，尤其是带延性铸造件装配式防屈曲支撑在延性铸造件增设卡套后，改变了试件破坏模式，实现了将非弹性变形定位于耗能段和BRB，形成“两阶段”耗能。发现轴力比取值在0.85~1.05、轴力超强系数取值在0.78~1.3之间、耗能段宽厚比取7~10、耗能段长度取值为铸造件长度的25%~35%时，结构滞回性能稳定，曲线较为饱满，耗能系数稳定在1.99~2.69 之间。结合三折线骨架曲线模型与正反卸载刚度退化规律，给出了带延性连接件的装配式全约束型支撑的恢复力模型。通过对带延性铸造连接件的中心支撑钢框架结构的试验和有限元分析，得出相应新型结构的承载能力、倒塌机理、耗能能力、塑性开展与分布及改进型特殊支撑的受力状况。给出了基于性能的带延性铸造连接件的特殊中心支撑钢框架抗震设计指标。结果表明结构具有良好的承载能力、刚度和延性，延性比在4.75～8.69之间，且塑性主要集中在延性连接件上，说明该结构具有良好的抗震性能。同时，在中心支撑防屈曲钢框架上对可替换连接件进行了替换试验，验证了对耗能连接件进行替换是可行的。说明将延性铸造连接件引入中心支撑框架后，不仅实现了将结构非弹性变形集中于延性连接件耗能段的目标，也能达到震后损坏延性铸造件易于替换和降低修复成本的目的。