Failure characterization of a structural welded component of an ancient bridge

摘要

The development of railroads promoted the innumerable railway bridges building in Brazil mainly at the end of 19th and the beginning of the 20th century. In those period, girders and other bridges components were built with a growth production demand promoting challenges in the control and volume of manufacturing production process taking into account that the metallurgical knowledge was in early stages. Nowadays, innumerable railway bridges are still in service and their proper maintenance is sometimes ignored. Thus, this work determine the type of metallic material and failure mechanism of structural arch and "L" shapes girders components from Desengano Bridge taking into account that some repairs were performed during their life span. The investigation conducted in this work showed that the structural components analyzed were constructed by puddle or wrought iron process, which is characterized by high levels of P and S in their composition. Meanwhile a reinforcement plate welded to the arch girder was added in a corrective maintenance of the bridge, especially because the plate material matches the current structural low carbon steel. The fracture surface revealed that the crack has dendritic inclusions with typical hot solidification crack aspect. Finally, it should be considered that metallic parts of any ancient bridge, especially those ones containing rivets as an essential rule, in first instance cannot be repaired in situ by welding.