强震作用下竖向不规则结构的延性折减系数研究

DUCTILITY REDUCTION FACTOR FOR VERTICALLY IRREGULAR STRUCTURES UNDER STRONG EARTHQUAKE ACTIONS

通过修正参考竖向规则结构的抗震延性折减系数,研究竖向不规则结构在速度脉冲强震作用下的延性折减系数。采用集中质量剪切型多自由度模型,阐述了速度脉冲地震作用下竖向规则结构延性折减系数运用于竖向不规则结构的修正系数研究方法,分析了该修正系数的影响因素。分析结果表明,竖向不规则结构的延性折减系数明显小于参考规则结构的延性折减系数。修正系数的主要影响因素是不规则比率和延性系数,其随着不规则比率减小或延性需求增大而减小。周期和楼层数对该修正系数的影响较小。同时,通过比较得出,速度脉冲地震作用下修正系数比相应非速度脉冲地震作用下修正系数值小。最后,通过对计算结果取平均值,给出了修正系数的建议值,并与欧洲抗震规范中修正系数的取值进行了比较。

Seismic ductility reduction factor was investigated in this paper for vertically irregular structures subjected to pulse-like ground motions. It was expressed as the production of seismic ductility reduction factors for vertically regular structures and a modification factor. Based on multi-degree-of-freedom(MDOF) lumped mass shear type models, the method to determine the modification factor was introduced, and its influencing factors were investigated. The results show that ductility reduction factors for vertically irregular MDOF systems are clearly smaller than those for vertically regular MDOF systems. The modification factor mainly depends on irregularity ratio and ductility ratio; the smaller the irregularity ratio or the larger the ductility ratio, the smaller the modification factor; while the influence of storey number and fundamental period is small. In addition, the modification factors for structures under velocity pulse-like ground motions are less than those under non-pulse-like ground motions. At last, the average results were suggested as modification factors, which were compared with the values specified in European seismic code.