Effect of overweight trucks on fatigue damage of a bridge

Abstract

Overweight trucks affect the fatigue life of a highway bridge. The stress range increases substantially if trucks are overloaded. Despite of existing regulation of permissible limits of Gross Vehicle Weight (GVW), overloading of trucks is widespread in India. Fatigue is a great concern to bridge engineers especially with the use of high strength steel and concrete for the construction of bridges. In this paper, the effect of overloading on fatigue damage of a highway bridge is studied. The aim of this study is to observe the relationship between prevalent truck overloading and fatigue damage accumulation. The fatigue damage accumulation is calculated for the steel longitudinal girder of a four span continuous steel-concrete composite girder bridge of length 119 m subjected to cyclic loading due to actually weighed overloaded trucks and trucks loaded with permissible GVW as specified in IRC guidelines. From the fatigue damage analysis it is found that the increase in truck weight of 50 % would lead to an increase in fatigue damage accumulation of 80 % in the steel longitudinal girder of road bridges. The relationship between fatigue damage accumulation and overload factor is non-linear. The findings of the study will be useful for fatigue design of bridges especially which are on port connectivity or near to mines and heavy industrial area, where overloading of trucks is prevalent.