Damage Mechanism Investigation of Trussed Combination Arch Bridge by FEMLIU Li-sheng1,YANG Da-peng1,WU Dai-hua1,CHENG Zhu-jiang2 (1.School of Sciences,Wuhan University of Technology,Wuhan 430070,China;2.Guizhou Communication Science Research Institute,Guiyang 550014,China)A three-dimension finite element model of Qingshui Bridge has been built for investigating the damage reason of trussed combination arch bridge.Two different conditions was considered.One was all prestressing+dead load and the other was part of prestressing+dead load.The first and third principal stress under those two conditions had been obtained by numerical analysis.The damage regions that calculated by numerical results were coincident with the investigation report by Guizhou Communication Science Research Institute.The irrational design of initial pre-stress may be a key factor that causes the damage of this bridge.trussed combination arch bridge;crack;pre-stress;FEM