Investigation and repair plan for abraded steel bridge piers: case study from Japan

This paper reports on a forensic investigation following the collapse of the Iwama Ohashi Bridge over the Shimanto River in Japan. The central section of the bridge failed in 2017 when a steel pier buckled. The investigation included thickness measurements using a new ultrasensitive magnetic non-destructive device. This revealed that the buckled pier and other bridge piers had been significantly abraded by fast-moving gravel. As a result, the steel plate of the downstream faces near the riverbed was considerably thinner than the upstream faces. The measurements indicated that the other piers were also likely to buckle in the near future if left unattended. This paper describes the details of the investigation and discusses a potential repair and reinforcement plan.