Effect of Cycle-Counting Methods on Fatigue Evaluation of Railway Bridges

Abstract

The effective stress range (ESR) and the number of stress cycles (NSC) are two key parameters in fatigue damage evaluation. The inaccuracies in predicting remaining fatigue life can be attributed to either one of these two parameters. A sensitivity analysis is described to address the effects of four cycle-counting methods on ESR and NSC for various fatigue details, which including rain-flow counting (RF), mean-crossing-peak counting (MCP), level-crossing counting (LC) and simple-range counting (SR). Using field monitoring data under normal traffic of Wei River Bridge, the comparative results of four methods showed that RF was more conservative than MCP and SR. The relationships between RF and other three counting methods were determined in the form of a correlation coefficient and a linear regression line. Therefore, values obtained for ESR and NSC by MCP, LC and SR can be converted to values for RF, which is used for comparison and transformation of fatigue life evaluation results using different cycle-counting methods.

Fatigue strength of an over one hundred year old railway bridge

“…Since railway bridges and viaducts operate under variable cyclic loading, the basic strength parameter responsible for their bearing capacity is the fatigue strength of the material used for the structural elements. Although there are many studies concerning the fatigue evaluation of steel bridges, especially railway bridges (Frýba 1980;Imam et al 2007Imam et al , 2008Škaloud, Zörnerová 2005;Wang, Hao 2011) and failure of railway infrastructure (Robinson, Kapoor 2009), it is essential to analyze various problems related to the fatigue strength of old, still operating railway bridges. Studies are necessary to determine the fatigue strength of various structural steels used in Poland since the early nineteenth century and the load-bearing capacity of bridge-type structures, including the actual strength parameters of the material.…”