Fatigue Life Assessment of Early Steel Bridges on Indian Railways

Investigations have been undertaken to develop rational norms for evaluation of residual fatigue life of early steel-steel prior to 1895 bridge girders in Indian Railways. This will facilitate undertaking of systematic rehabilitation of these bridges which over the years have been loaded to more demanding conditions than for which they were designed. Fatigue life studies on the sample specimen from inservice/released girders and on the influence of variation in chemistry, climatic conditions and fabrication/construction techniques have yielded S-N curves for girders in the coastal region of the country and a methodology using Miner's hypothesis for prediction of residual fatigue life has been recommended for use. A few technical applications on the Indian Railways and application of fracture mechanics concepts and feasibility of using NDT techniques in the field for monitoring the fatigue performance are presented in this paper.