Abstract:
This research addresses the issue of high-cycle fatigue in the connection details of steel bridges built before 1960, which are nearing the end of their service lives. The goal of this study was to develop a methodology to identify problematic details before they develop visible cracks, thereby guiding inspection and repair efforts and significantly reducing costs. The study focused on the Winchester Bridge in Oregon, which has a history of high-cycle fatigue problems in its flooring system connection details. The project utilized finite element analysis (FEA) extensively, employing multiple modeling approaches to characterize the bridge's structure and assess the forces on its components. A global FEA model was created to analyze the distribution of truck loads on the stringers, validating the results with field-collected strain data. Subsequently, 2D and 3D FEA models were developed to quantify the deflections and stress ranges within the clip angles that connect the stringers to the floor beams. These models investigated the effects of various factors, including element density, boundary conditions, rivet pre-load, friction, and clip angle thickness. The stress ranges derived from these detailed models were then used in two different fatigue analysis methods—stress-life and linear-elastic fracture mechanics (LEFM)—to estimate the remaining fatigue life of the connection details in years. The analysis results, although found to be very conservative compared to the actual bridge’s condition, led to the development of a low-cost field identification methodology and the evaluation of five different retrofit strategies. The study concludes with recommendations for future work, including further field validation to better quantify the composite action between the concrete deck and the steel structure to improve the accuracy of the FEA models and fatigue life predictions.
