Cause identification of the fracture in steel pipe column of a pedestrian bridge and its retrofitting

A Serious fracture that extended halfway through the circumference of a steel pipe column was discovered in a pedestrian bridge across a prefectural road. A lot of pedestrian bridges have been designed and constructed according to the standard specifications. Therefore, there is a possibility that pedestrian bridges whose structural details are the same as those of fractured pedestrian bridges in this paper may exist. It is very important to identify the cause of the fracture for preventing the same failure mode. In order to identify the cause of the fracture, observation of crack surface, SEM observation, material property tests, measurement of strain and calculating histogram of the stress range and the frequency were carried out. Moreover, the fractured steel pipe column of the pedestrian bridge was retrofitted by applying bolted splice rings and plates.