Investigation of Bridge Pin Failures

摘要

Severe corrosion, cracking, and even failure of the pins used in bridges having the pin and hanger strap connections have occurred in a number of bridges throughout Missouri. The results of a metallurgical examination to determine the mechanism of cracking and fracture of these pins are presented. The research suggests that the failure mechanism occurs by a combination of corrosion and corrosion-originated overload. The corrosion on the pin is particularly severe at the interface between the hanger strap and web section where corrosion is accelerated by the accumulation and retention of salt-laden moisture. The corrosion in the pin is also accelerated by the presence of high stresses in the pin. Eventually the combination of stress and corrosion of the pin at the interface between the hanger and web causes a crack to nucleate and grow. Once the crack nucleates, growth accelerates due to additional corrosion and reduction of the cross-section until failure finally occurs.