Probabilistic Fatigue Life Assessment of Existing Steel Railway Bridges

Abstract

A new probabilistic fatigue life assessment (PFLA) procedure for steel railway bridges is proposed in dual response surface method (DRSM) framework. The uniqueness of the proposed PFLA is its capability of yielding accurate fatigue life prediction with significantly lesser computational time than that required by conventional stochastic simulation-based PFLA approach. The proposed procedure considers the actual behaviour of a bridge at site through a simple and quick total station surveying-based experimentation. The derived correction factor has successfully tracked the failure of a steel bridge. Unlike the conventional approaches, the proposed PFLA captures more detailed description of uncertainty by considering cumulative distribution function instead of spectrum-equivalent mean for evaluation of endurance limit. The record-to-record variation of live load time-histories iseasily considered by DRSM. The efficiency of the proposed PFLA procedure is elucidated with seven real-life bridges. The proposed procedure is observed to be consistently accurate as well as computationally efficient, when compared with the most accurate stochastic simulation-based PFLA and actual fatigue lives of the considered bridges. The conventional deterministic fatigue life assessment procedures are observed to yield significantly erroneous results in this regard.The proposed procedure is quick, and does not require expert manpower, costly equipment, and workstations. Rather, widely available software like STAAD.Pro, MS Excel, and total station surveying instrument are sufficient for implementation of the proposed PFLA.The proposed procedure is applicable for any railway bridgesand extendable to other complex steel structures. Thus, this procedure will be relevant to practicing engineers for routine fatigue safety monitoring of millions of railway bridges,simultaneously, with least cost and resources, indigenously, towards fulfilment of the Atmanirbhar Bharat mission.