承载力退化体系中不同延性系数下的地震力计算

THE CALCULATION OF SEISMIC FORCE WITH DIFFERENT DUCTILITY FACTOR IN STRENGTH DEGRADING SYSTEM

摘要:

对承载力有退化的修正理想弹塑性（EPP）滞回模型、剪切滑移（SSP）滞回模型和双线性（BIL）滞回模型的SDOF体系在地震作用下进行弹塑性动力分析，得到了不考虑和考虑承载力退化时不同场地、延性系数等参数组合下的双周期标准化的地震力调整系数R谱，计算了承载力有退化的修正EPP模型的基底剪力影响系数谱 ，提出了αEK谱的简化计算公式，用以分析承载力退化对基底剪力的影响，进而得到与退化模型等效的理想弹塑性模型。结果表明：承载力退化对BIL和SSP模型的影响不大，对修正EPP模型的影响则随退化值增大而增大。实践中对退化的修正EPP模型，应采用与延性系数定义相配套的地震力折减系数。对于和理想弹塑性模型延性等效的承载力有退化的结构体系，其承载力是理想弹塑性模型的αEK倍数，同时变形能力需求也为理想弹塑性模型的αEK倍。

Abstract:

This paper analyzed the seismic force modification factor R of strength degrading modified elastic-perfectly plastic (EPP) model, bilinear elastic (BIL) model and shear-slipped elastic-plastic (SSP) model for different site and ductility factor. The system coefficient spectra of base shear were constructed to analyze the influence of the degradation of strength on seismic force modification factors. An ideal elastic-plastic model is proposed which is equivalent to the degradation model. Results reveal that the strength degradation has almost no influence on the R spectra of BIL and SSP model, but for modified EPP model, its influence increases with the degradation and cannot be neglected. When taking the strength degradation to define the ductility factor in practice in modified EPP model, it is necessary to adopt a ductility-definition-related strength reduction factor. For the strength degrading system, the strength demand and the deformation-capacity demand are found to be αEK times of the ideal elastic-perfectly plastic model.