连于人字形防屈曲支撑的横梁抗震设计探讨

STUDY ON SEISMIC DESIGN OF THE BEAM CONNECTED BY THE CHEVRON BUCKLING-RESTRAINED BRACES

通过3个算例,对采用人字形无粘结内藏钢板支撑剪力墙(即人字形防屈曲支撑)的防屈曲支撑框架结构的抗震性能进行对比分析,以探讨支撑屈服后超强和被撑梁跨中竖向支点作用的有无对支撑跨横梁抗震性能的影响。结果表明,3个算例的框架梁在多遇地震下均能保持弹性,且被撑梁的最大竖向挠度均出现在撑点两侧。罕遇地震下,3个结构中支撑屈服后被撑梁的最大竖向挠度均出现在撑点位置。考虑超强但不考虑支点作用设计的结构中框架梁塑性发展程度较小,而不计超强但考虑支点作用设计的被撑梁塑性发展严重,且横梁的挠度较大,导致层间的两根支撑因承受较大的竖向力而使拉、压支撑的轴向应力-应变曲线明显不对称,不利于支撑受力。

A seismic response analysis is carried out in order to compare the aseismic performance of three buckling- restrained braced frames （BRBFs）. The effects of the two factors, including overstrength of the postyield buckling-restrained brace （BRB） due to the strain-hardening effect and the vertical support for the braced beam by this brace, on the aseismic performance of the beam braced by the chevron unbonded steel plate brace encased in reinforced concrete panel （ so-called chevron BRB） are discussed. The analysis reveals that the beams in the three structures remain elasticity under frequent earthquake. The maximum vertical deflection of the beam connected by the chevron braces occurs in the segments of beam between the column and braced points before the brace yielding. Under severe earthquake, the maximum vertical deflection of the braced beams occurs at braced points. The beams designed by taking account of support action of braces but omitting the overstrength of braces develop large plastic deformation, resulting in the slightly larger deflection of the connected beams and the larger vertical gravity forces supported by the chevron BRBs, which make axial plastic deformation of the brace in compression be larger than that of the brace in tension. Whereas, little plastic deformation occurs in the beams designed by taking account of the overstrength but omitting the support action of the braces.