FATIGUE ANALYSIS OF STEEL BRIDGES UNDER MOVING LOADS

Abstract

Steel bridges are subjected to stress fluctuations under the influence of moving loads and consequently dominant failure modes arise from fatigue under normal circumstances. The objective of this study is to assess fatigue life of railway steel bridges subjected to moving train loads. Fatigue life expectancy of three plate girder and three welded truss type bridges having spans ranging from 12m to 61m have been evaluated. These bridges have been designed as per Codes of Indian Railway Standards for Steel Bridge and Bridge Rules. Palmgren-Miner linear damage rule with the rainflow counting technique has been used to quantify the fatigue damage. The study indicates that the longer span bridges have longer fatigue life than the shorter span bridges. The study indicates that the steel bridges in use today have substantial fatigue life. The study also indicates that the Palmgren Miners rule provides life expectancy on conservative side.