偏心隔震结构扭转效应机理分析及关键参数限值研究

Research on mechanism of torsional effect and limits of critical parameters of asymmetric base-isolated structures

相较于传统抗震结构,隔震结构更易通过调整隔震支座布置方案,控制关键参数在合理范围内,减少上部结构偏心带来的不利影响。为此,从偏心隔震结构扭转效应机理角度,分析了在不同取值范围内,隔震结构转侧频率比、隔震层偏心率对扭转效应的影响规律和影响程度。研究结果表明:转侧频率比越小,扭转反应越明显,且此时较小的隔震层偏心率就会使得隔震结构扭转加剧;当转侧频率比大于1.2后,其影响逐渐减弱;隔震层的偏心率与扭转响应接近正相关。然后,以支座位移不超过容许值为限制条件,推导出距离质心最远处支座在有无偏心时的位移比值显式。分析结果表明,存在一个最大隔震周期使该比值取得极小值。据此,可推导出不同转侧频率比时隔震层偏心率的限值,在该限值范围内偏心隔震结构的扭转可得到有效控制,为设计人员在进行隔震结构抗扭设计时提供参考。

Compared with traditional seismic structures,it is easier to control the critical parameters in a reasonable range by adjusting the layout of isolators,so as to reduce the adverse impact caused by superstructure eccentricities.Therefore,from the perspective of the torsional mechanism of asymmetric base-isolated structures,the influence law and degree of the torsional to lateral frequency ratio of base-isolated structures and the eccentricity in the isolation system on the torsional effect in different value ranges were analyzed.Results show that,the smaller the torsional to lateral frequency ratio is,the more obvious the torsional response is,and the small eccentricity in the isolation system will aggravate the torsional response.Torsional response is weakened when the torsional to lateral frequency ratio is greater than 1.2,and the eccentricity in the isolation system is close to a positive correlation with torsional response.Then,the explicit limit displacement ratio of the furthest isolator from the center of mass with or without eccentricity was derived under the condition that the displacement of isolator did not exceed the allowable value.The results of analysis indicate that there is a maximum isolation period to make the limit value obtain a minimum value.According to this,the limit value of the eccentricity under different torsional to lateral frequency ratios can be obtained,and the torsional response can be controlled within the limit range effectively,which provides effective references for designers in torsional design of asymmetric base-isolated structures.