防屈曲支撑-钢筋混凝土框架结构基于能量平衡的抗震塑性设计

Seismic plastic design of buckling-restrained braced-RC frame structures based on energy balance

为确定防屈曲支撑在结构中的布置方式以使结构抗震性能充分发挥,提出了基于能量平衡的防屈曲支撑-钢筋混凝土框架结构抗震塑性设计方法。构建了结构的"强柱弱梁"整体屈服机制,采用侧力比将总结构体系离散为防屈曲支撑体系和纯框架体系,并建立了结构的双线性能力曲线。基于能量平衡方法计算结构的设计基底剪力并分别得到支撑体系和框架体系的设计侧向力,进而完成支撑的截面设计。按照塑性内力分配机制和考虑支撑屈服后性能,计算梁柱构件内力需求。以一幢5层结构为例,分别设计了不同侧力比的14个结构模型,对比了基底剪力、防屈曲支撑面积和梁柱钢筋用量等。通过22条地震波下的弹塑性时程分析,研究了不同侧力比结构的最大层间位移角、屈服机制、楼层剪力比、支撑最大位移延性、累积位移延性和结构残余层间位移角。分析结果表明:所提出的方法能实现结构的预期失效模式,并满足结构的抗震性能要求,并建议设计侧力比选取在0.3~0.5之间。

To determine the buckling-restrained brace （BRB） configuration in structures to fully exploit the seismic performance, an integration plastic design method of buckling-restrained braced reinforced concrete frame （BRB-RCF） structures was developed based on energy balance in this paper. The ＇strong-column weak-beam＇ global yield mechanism was constructed and the total BRB-RCF system was decomposed into BRB system and RC frame system by using the lateral force ratio, and the bilinear capacity curve was derived. The design base shear was calculated based on an energy balance method to determine the design lateral forces of BRB system and RC frame system, and then the section design of BRBs could be completed. According to the plastic design method and considering the post-yield behavior of BRBs, the internal force demands of beams and columns could be calculated. Using a ftve-story structure as a prototype, 14 frames with different lateral force ratios were designed, and the design base shears, BRB section areas and reinforcements of RC columns and beams were compared. By performing the nonlinear dynamic analyses under 22 ground motions, the maximum inter-story drift ratio, yield mechanism, story shear ratio, the maximum and cumulative displacement ductility of BRBs and the residual drift ratio were systematically investigated for structures with different lateral force ratios. The analytical results show that the proposed approach can achieve the desired seismic failure modes and meet the performance requirements, and the design lateral force ratio between 0.3-0.5 is suggested.