Structural Deterioration Assessment for Steel Bridges

Abstract

A rational approach for evaluating structural integrity of aged and deteriorated steel bridges—incorporating analytical, mechanical, and microstructural characterizations—is presented. Critical regions of built-up members, salvaged from decommissioned truss bridges, were identified using structural finite element analysis and the results guided the sampling process for microstructural analysis. A set of mechanical and metallurgical characterization procedures were designed to understand the mechanical history of critical sections of the structure. Observations made on the microstructure of a naturally stressed region revealed segregation of pearlite and MnS inclusions and flow of grains. The mechanical flow and microcracks observed in the stress-concentrated tensile region of the member indicate a high probability of eventual brittle failure of the material. Since stress-assisted aging seems to affect the microstructure, this may be used as a means of unobtrusive testing for susceptibility to failure. It follows that the microstructural analysis procedure, to detect stress-assisted aging and failure, may serve as a novel field-evaluation technique for aged steel structures.