Structural Appraisal-based Different Approach to Estimate the Remaining Fatigue Life of Railway Bridges

Abstract

The current fatigue life estimation methods of railway bridges are generally based on combinations of measured strain histories, Miner’s rule, and railway code provided fatigue curve. Even though the past measured strain histories are available for major bridges, most of the old bridges do not have past strain measurements. Furthermore, in case of existing railway bridges where the detailed loading history is known, Miner’s rule might provide incorrect results because of its omission of load sequence effect. These reasons hinder the usage of current methods to estimate the realistic remaining fatigue life of most of the existing railway bridges. Therefore, a new method is presented in this article to estimate remaining fatigue life of riveted railway bridges. The method mainly consists of predicted stress histories, recently developed sequential law and fully known Wöhler curve. Here, it is essential to use the fully known Wöhler curve as the related fatigue curve. Hence, the technique, which utilizes transfer of the partially known Wöhler curve to fully known curve, is also discussed in this article. Further, this method describes a reasonably accurate procedure to obtain the past stress histories from present day measured strains. Initially, the article describes the proposed method for remaining fatigue life estimation. Then the sequential law and associated fully known S-N curve determination procedure are verified by comparing theoretical fatigue life, damage behavior with real fatigue life and damage behavior of few materials. Finally, the remaining fatigue life of an existing railway bridge is estimated. Hence, validity and merits of the proposed method is confirmed by comparing the results with previous method-based fatigue lives.