近断层竖向强震作用下混凝土框架柱轴力分布模式研究

Research on the Distribution Mode of Axial Force for RC Frame Columns Subjected to Near-fault Vertical Ground Motions

研究近断层竖向地震作用下混凝土框架柱轴向内力的变化规律,解析结构抗震性能衰减以及坐层倒塌的本质.采用一榀3跨10层混凝土平面框架结构作为分析对象,通过动力时程分析,探讨2种水平和6种竖向地震强度的组合工况时,混凝土框架柱轴压力增量分布模式及拉力的变化规律.结果表明,有竖向地震作用参与的工况,框架柱轴压力能达到初始值的2～3倍,竖向地震作用对结构上部框架柱以及框架边柱轴力的影响显著;竖向地震频率特征对框架柱轴力有很大影响,我国抗震规范建议通过缩放水平地震而获得竖向地震的方式进行竖向地震响应分析,可能低估竖向地震对结构动力反应的影响.

The variation trend of column axial force of reinforced concrete frame structures subjected to near-fauh vertical and horizontal ground motions is studied, and the mechanism of seismic behavior degeneration and the storey pancake collapse of the structure is analyzed. Employing a 10 - storey 3 - span planar frame as the analytical objective, the dynamic history analyses are performed to investigate the distribution mode of the incremental axial force of the frame column under 2 horizontal intensities and 6 vertical intensities of ground motions. The results show that the compression force of column can be 2 - 3 times of the initial static force due to the vertical ground motions. The vertical ground motion has greater effects on the exterior frame columns and the upper columns of structure. The frequency content of the vertical excitation has important effects on the column axial force; the vertical earthquake analysis using the scaled horizontal ground motions recommended in current seismic codes should under-estimate the effect of vertical excitation.