建筑结构抗震设计扭转周期比控制指标研究

研究扭转周期比作为结构扭转控制指标的有效性。分析了扭转周期比对结构扭转效应的影响,讨论了扭转周期比作为扭转控制指标的合理性。在OpenSees平台上采用基于柔度法的纤维模型,对不同扭转周期比的计算模型进行了弹塑性动力时程分析,分析了扭转周期比作为扭转效应控制指标的有效性。弹性分析表明:扭转位移比能反映结构扭转效应;扭转周期比仅对相对偏心距较小的规则结构起控制作用;对考虑偶然偏心的扭转位移比进行限制后,无须再对规则结构的扭转周期比进行控制。非线性反应分析表明:结构的扭转非线性反应受弹性最大层间位移角的控制最为明显,受扭转周期比控制不明显。建议在有效控制扭转位移比的前提下取消扭转耦联周期比限制。

Study on torsional period ratio control index for seismic design of building structures

The rationality and necessity of period ratio of the 1st torsion mode to the 1st translation mode as a control index for seismic design of structures were discussed.The influence of the period ratio on structural torsion response was analyzed.The fiber model based on the finite element flexibility method in OpenSees was employed to analyze the nonlinear torsion response of RC frame structures with various period ratios by nonlinear dynamic time-history analysis.The results of elastic analysis show that the torsional displacement ratio is an expression of torsion effect and the period ratio of torsion mode to translation mode is only one of factors influencing torsion response,and is only valid for structures with relatively small eccentric ratio and need not to be controlled for regular structures with small eccentric ratio when the displacement ratio is controlled.The results of nonlinear analysis show that structural nonlinear torsion response is related directly to the maximum elastic inter-story drift ratio between floors but not the period ratio of torsion mode to translation mode.It is concluded accordingly that the limitation of the period ratio in current code can be cancelled in some conditions.