With increasing the huge number of aged infrastructures stock built during the period of rapid economic growth, in late years it is reported that the serious damage of steel bridges such ad a diagonal meember fracture or the collapse accident. It is necessary to develop a rational maintenance management system. In addition, it is also necessary to evaluate appropriately loading capacity based on data of the damage. In steel truss bridges, neighborhood of connections could be a weak point of structural system due to stress concentration or secondary stress. This paper focuses the deceasing the thickness of gusset plate due to the corrosion, and ultimate strength of bridge structures are evaluate by FEM. Two type numerical models were prepared to compare the result of consideration for with or without the corrosion in the analysis, and only gusset plate thckness is reduced as assumed the corrosion. The results showed that structural system becomes unstable with buckling of upper chord member in no corrosion model. On the other hand, ultimate strength of contrast in 50%corrosion model which was reduced the thickness of gusset plate by half decreased 20% due to unstable with out-of-plate buckling of gusset plate. |