Life evaluation of critical members of steel bridges located in different atmospheres

Abstract

Abstract: Most of the iron and steel bridges in Sri Lanka are more than 100 years old. Since many of them are reaching or exceeding their design lives, the risk of collapsing those bridges have increased. One of the probable damages which bridges experience due to increasing traffic volume as well as environmental degradations such as corrosion is the corrosion fatigue failure. This problem is severe in bridges located in industrial areas and along the coastal line of the country. Corrosion and corrosion fatigue made a huge attention in the recent past due to many failures of bridges all over the world. This paper presents a study conducted on assessing the corrosion fatigue damage of steel bridges. It proposes a procedure developed using existing fatigue and corrosion models for evaluating the remaining fatigue life. The procedure includes condition surveys, field loading tests, finite element modelling and analysis, developing S-N curves for different atmospheric conditions, use of corrosion rates and assessing cumulative fatigue damage. The paper also presents a case study: a century old iron and steel (mild steel and wrought iron) railway truss bridge damaged by both corrosion and fatigue. Using details of condition survey, load testing, appropriate corrosion data, finite element modelling and a corrosion fatigue assessment procedure, the remaining life of the bridge was evaluated for two atmospheric conditions; (i) corrosive atmosphere and (ii) noncorrosive atmosphere. The results of the evaluation were then compared to show the impact of the atmospheric condition on the fatigue life of the bridge.