Assembly procedures of trunnion-hub-girder for bascule bridges

This work is concerned with avoiding failures during the assembly of a trunnion-hub-girder (THG) for bascule bridges. In the current assembly procedure, AP#1, the trunnion is shrunk fit into the hub, followed by the shrink fitting of the trunnion-hub assembly into the girder. Two separate incidents during assembly prompted this study. The first incident involved the development of cracks in the hub during the assembly process using AP#1. The second incident involved the trunnion getting stuck in the hub before the trunnion could be fully inserted. A complete analytical, numerical, and experimental study was conducted to understand these failures, and the results were used to develop specifications and recommendations for assembly. The causes of failures include the development of high stresses at low temperatures. during assembly, while noting that fracture toughness of THG materials decreases with temperature. Recommended specifications included following an alternative assembly procedure that nearly doubles allowable crack length, and that lowers cooling temperatures to avoid trunnion sticking in the hub. (C) 2003 Elsevier Ltd. All rights reserved.