RESIDUAL LIFE ASSESSMENT OF STEEL BRIDGES UNDER THE COUPLED ACTION OF CORROSION AND FATIGUE

Abstract

Truss bridges are one of the most typical configurations used for the medium to long-span steel bridges. Under railway loading, such bridges are subjected to reversal of loads, leading to fatigue damage. Fatigue is a serviceability limit state criterion. Therefore, excessive deflection may cause discomfort, rendering the bridge to be unserviceable. Fatigue life is affected by corrosion, as corrosion reduces the net section available for resistance and also affects the regions of connections and bearing locations. Pitting corrosion in small areas leads to formation of the small undulations, which on application of fatigue load develop as cracks. These pits act as stress raisers, which leads to stress concentration. Along with this, the residual stress acts as a base about which stress reversals take place. Residual stresses and material reshaping leads to crack initiation, these cracks elongate when subjected to stress reversals. The coupled study of corrosion along with fatigue in a time-based manner needs to be conducted to evaluate the service life of the structure. Additional elements like stiffeners, connection angles are crucial in design for corrosion fatigue. The increase in the speed of trains and freight load on existing truss bridges, presents a precarious situation of assessing the residual life considering the deterioration. Hence, in this study, it is intended to develop a numerical model of a truss bridge span, subjected to corrosion using currently available codes. The target of the present work lies in the investigation of effect of steel corrosion in degradation of strength and establishing a suitable approach to determine the couple effect of corrosion and fatigue in the deterioration of service life of steel bridges.