Nene Yamamoto

Analytical study on evaluation method of soundness of diagonal members of the truss bridge with corrosion break

Eiji Iwasaki

 Corrosion is one of the primary deterioration cause of steel truss bridges. The compressive diagonal members of them are constituted by fillet welding using steel plates. These diagonal members are designed, in which occurs neither global buckling of the column nor local buckling of the plate under the action of the load. When the welds of the plate constituting the compressive diagonal members are separated off by corrosion, then the broken part of the plate (corrosion break) becomes the free side. For that reason, the local buckling strength of the plate decreases. But, it has not established yet evaluation method of soundness of the damage of corrosion break members. 
 Therefore, the purpose of this paper is to propose the method for evaluating the soundness of corrosion break members. First, we proposed the level division focused on the buckling stress of a corrosion break member and the repair policy of them. Second, we performed the elastoplastic buckling analysis of corrosion break members and evaluated the soundness of them. This evaluation method can catch the soundness of them without relying on the experience of engineers and clarify the priority and urgency of repair for bridges.
 However, elastoplastic buckling analysis is complicated and takes a long time to analyse. Thus, I performed the regression analysis of the results of the elastoplastic buckling analysis of corrosion break plates and proposed the ultimate strength curve of the corrosion break plates. This paper obtained the local buckling stresses of the corrosion break members using the created curve. Furthermore, I proposed a new method to obtain the coupled buckling stress by calculating the local buckling stress of each of the four plates that constitute the diagonal member and comparing the minimum value of them with the global buckling stress. This method can calculate the coupled buckling stress more accurately than the product formula and Q-factor method.