INFLUENCE OF SUPPORT FLEXIBILITY ON FATIGUE ANALYSIS OF STEEL RAILWAY BRIDGES

Abstract

Fatigue is undoubtedly the most important failure mode in any engineering structure. Structures like Railway steel Bridge are subjected to stress fluctuations under influence of moving train loads and as a result the bridge members are highly susceptible to fatigue failure. The objective of this study is to assess support flexibility on fatigue life of steel railway bridges subjected to different type of train loads. Fatigue life expectancy of three plate girders and two welded truss bridge stringers as well as one welded truss bridge having spans ranging from 12m to 76.6m have been evaluated with two support condition i.e., one is rigid support and other is flexible support. In the flexible support, three_ springs are rested on three different directions (horizontal, vertical, rocking). These bridges as well as support have been modeled as per codes of Indian Railway Standard for steel Bridge rules. Palmgren-Miner liner damage rule with rainflow counting technique has been used to quantify the fatigue damage. The study indicates that the longer span bridge with flexible supports have longer fatigue life than shorter span bridges. Life of the bridge is more when it rests on flexible support as compared to rigid support