Effect of measurement uncertainties on strain-based damage diagnostics for highway bridges

Abstract

Diagnostic load rating of highway bridges using distributed strain transducers is one of the more prominent strategies applied for both periodic and continuous monitoring of highway bridges. Techniques for load rating structures using experimental measurements of neutral axis locations, girder distribution factors, and dynamic increase factors have been suggested for structural health monitoring and damage detection applications. However, practical considerations related to the influence of measurement uncertainties on the reliability of these diagnostic measures in the presence of damage have only been examined recently. This paper extends uncertainty propagation formulae previously derived for neutral axis measurements to girder distribution factors. The significance of measurement uncertainties on damage-sensitive features are then explored using experimental data from a real bridge subjected to progressive, prescribed damage. The experimental results suggest that both apparent neutral axis locations and girder distribution factors exhibit sensitivity to the damage mechanisms introduced that exceeds the measurement uncertainty. In addition, girder distribution factors are found to demonstrate the ability to locate the damage. Comparisons with finite element simulations underline the challenges associated with faithfully modeling the effects of structural damage and emphasize the need for continued full-scale validation of structural health monitoring approaches on real structures.