Hybrid approach combining modelling and measurement for fatigue damage estimation of welded connections in bridges

Abstract

The fatigue life of structural steel bridges is governed by the time history of in situ stresses at its fatigue-critical structural details under service conditions. However, these stresses are often not directly and accurately measurable due to the complex geometry of the detail or due to access restrictions. This article proposes a novel methodology to address this challenge. The methodology infers stresses at fatigue-critical locations by combining in situ strain measurements taken further away from a critical location in a full-scale bridge. Strains measured at various points around the physical welded connection are used to compute the forces and moments applied at the connection. These forces are then applied to a finite element model of the connection to predict the stresses that are required to evaluate the hot spot stresses. The developed methodology is illustrated for a welded connection in a full-scale bridge. Results show that the predicted time history of hot spot stress is accurate and much more realistic than those obtained from numerical simulations. Also, the study demonstrates that the proposed methodology is applicable for interpreting measurements from full-scale bridges and can be integrated within a measurement interpretation platform for continuous bridge monitoring.