群桩基础桥墩静力PUSHOVER分析

Static Pushover Analysis for the Pier with Group Pile Foundation

静力Pushover分析是应用能力谱法进行抗震分析的重要一步,也是研究结构非线性受力特征的重要方法之一。本文采用Pushover分析方法,同时考虑地基土与桩构件的非线性,研究了群桩基础桥墩的侧向加载模式与非线性受力特征。研究结果表明:(1)侧向加载模式不同,获得的能力曲线不同。均匀分布和墩顶集中力加载模式分别反映了结构能力曲线的上、下限,一阶振型和SRSS分布介于两者之间。建议群桩基础的Pushover分析应采用SRSS加载模式。(2)墩高小于20 m时,高速铁路简支箱梁桥的水平惯性力主要集中在墩顶及承台处。(3)受拉侧单桩初始屈服后,群桩基础的承载能力还可继续增加,但横桥向多排桩(4排桩)群桩基础增加更明显。横桥向多排桩群桩基础的位移延性系数高于纵向两排桩的情况。

Static pushover analysis is an important step to perform seismic analysis in the application of the capacity spectrum method and one of the most important methods for studying structural nonlinear properties. The lateral load pattern and non-linear mechanical characteristics for pile group foundation piers are discussed in this paper considering the nonlinearity of subsoil and piles component by using Pushover analysis. The results show that：（ 1） When the lateral load patterns are different,the capacity curves obtained are also different. Uniform distribution and concentrated loading pattern at pier top will represent respectively the upper and lower limit of capacity curves,but the capacity curves derived from the first mode and SRSS distribution will be in between. In pushover analysis for pile foundation,the SRSS should be used.（ 2） The horizontal inertial force is mainly concentrated at pier top and pile cap for simply supported box girder bridge on high-speed railway when the height of pier is less than 20 m.（ 3） After the initial yield of single pile under tension,the bearing capacity of group pile foundation can also continue to increase. But it will increase greatly for group pile foundation with multiple rows of piles in lateral direction. Displacement ductility coefficient for group pile foundation with multiple rows of piles in lateral direction is more than that of two rows of piles in longitudinal direction.