基于能量原理的框架桥墩地震力分析

Analysis for transverse seismic forces of the frame bridge piers based on energy principle

用 Lagrange方程导出了框架桥墩地震振动方程 ,并给出了相应的基频和振型参与系数的近似计算公式。根据框架桥墩结构特点构造基本振型函数 ,将框架桥墩的横向总变形分解为墩身的弹性变形与基础转动和平动所产生的刚体位移的叠加 ,其中弹性变形由墩顶水平推力和约束力矩联合产生。分别讨论了横向设置防震限位构造与不设限位构造对框架桥墩地震力的影响。研究表明 ,现行公路桥梁抗震规范方法计算值偏小。本文方法适应于各种基础类型的桥墩 。

The transverse seismic vibration equations of the frame bridge piers and approximate formulas for their basic natural frequency and influencing coefficient of their basic oscillation mode are derived by the Lagrange Equation.In the basic shape function,their total deformations are divided into three parts,i.e.the elastic deformations caused by a unit horizontal force and redundant moment at the top of frame piers,the deformations caused by the rotation and translation of the foundation.The effects of transverse structures against earthquake are discussed.The results show that transverse seismic forces are relatively small in using precautions against earthquake.The energy formulas presented in this paper are clear in concept,simple in computation and high in precision.Also,they are adaptable to frame bridge piers with different kinds of foundation.The reference base is given to revise the design specification of precautions against earthquake for highway bridges.