First of all,the nonlinear equation of structure is presented in this paper based on virtual work principle. It is thought that the Updated Lagrangian Formulation(U.L.Formulation) is more adapt for nonlinear analysis computer program for arch bridge.

• 首先，本文基于虚功原理，推导了结构几何非线性方程，指出更新的拉格朗日列士法(U.；L列士)更适用于桥梁结构非线性分析程序的编制。