钢筋混凝土框架结构抗层屈服倒塌能力评价方法研究

Study on seismic collapse resistance evaluation method of weak layer in RC frame structures

在框架薄弱层进入塑性工作阶段后,地震反应将大幅衰减,如地震持续作用,或者再遭遇较大余震时,结构可能会倒塌。通过分析钢筋混凝土框架薄弱层承载力退化和刚度退化,探讨发生落层倒塌的内部原因和外部条件,揭示框架薄弱层倒塌临界状态应遵循的变形准则和稳定准则。通过分析试验数据,阐述基本原理,推导计算公式,提出了基于Pushover分析的钢筋混凝土框架抗层屈服倒塌能力评价方法。研究结果表明,钢筋混凝土柱端弹塑性损伤是薄弱层承载力和刚度退化的内在原因,竖向荷载引起的等效负刚度是抗侧刚度丧失的外部条件;影响抗倒塌能力的主要因素包括竖向动力放大系数λ、刚度退化系数βu和刚重比ζ,当λ=βuζ时,框架薄弱层处于倒塌临界状态。最后提出了抗地震倒塌需进一步研究的问题。

Seismic action will be greatly attenuated after the yielding of weak layer of RC frame structures.And the structure will collapse when seismic action is sustainable or larger aftershocks occur.Through the analysis of strength and stiffness degradations of the frame weak layer,internal and external conditions of fall layer collapse were discussed.Deformation criteria and stability criteria of frame collapse yielding limit state were researched.Through the analysis of test data,basic principle,calculation formulas,seismic collapse resistance evaluation method of weak layer in RC frame structures based on Pushover was proposed.The results show that,RC column elastio-plastic damage is the intrinsic reason of degradation of weak layer strength and stiffness.the equivalent negative stiffness resulted from vertical load is the external conditions of the lateral stiffness loss.The main factors of collapse resistance include vertical dynamic amplification coefficient λ,stiffness degradation coefficient βu and rigidity-to-gravity ratio ζ,and framework layer yielding is in collapse critical state when λ=βuζ.Finally,the problems that may need further research on seismic collapse resistance are proposed.