NODES OF HOLLOW CORE PROFILE TRUSS BRIDGES WITH INCOMPLETE WELDS

Abstract

Among the various types of steel bridge girders, trusses seem one of the most powerful and reliable. The individual members may be simple, but the nodes are the complex parts, especially if more than 4 members are connected. In view of the complexity, internal welds become inevitable and are inaccessible after finishing, which is overlooked easily during construction. The proposal is to eliminate those of the inside welds that may be dispensable. If some of them would be eliminated, the consequences may be acceptable, or require minor modifications only. The assumption is tried out on the example of a structure replacing a historic bridge. This structure is composed of rectangular hollow profiles, connected at nodes. Member forces and bending moments, have been determined. If the internal welds are about to be eliminated, an alternative load path is found. The calculation of stresses in the various fillet welds is based on the assumption of evenly distribution of forces. The weld stresses can be calculated by the derived formulas. The results show some welds require strengthening, due to the elimination of the more complicated internal welds. This concerns ultimate limit state. Thus, the possibility is confirmed that some of the internal welds may be eliminated, although there still is no proof the method may be applied to more complex nodes. Research must be continued to clarify this. For the type of hollow core members being considered, omitting of some internal welds may well be an acceptable alternative.