The Use of Refined Analysis in the Evaluation and Determination of Load Capacity of Existing Steel Plate Girder Swing Span Bridges

Steel Plate Girder Swing Span Bridges are a common and traditional movable bridge type typically used in rural areas of Louisiana but can also be found all over the world. As a result of structural analysis code updates that reflect the increase in highway traffic loads and changes in analysis provisions, many of these bridges have become load posted due to deficient ratings using current traditional AASHTO bridge rating methods. This thesis will explore a more accurate load capacity of these bridges using two identical load posted bridges in Louisiana. Refined analysis methods such as finite element (FE) methods are known to capture the structural performance of complex structural systems in a way that simplified, e.g. two-dimensional (2D) models, cannot. The goal of this study is to demonstrate the feasibility of using calibrated refined analysis methods to remove load postings established using traditional load rating methods. Load testing and finite element analysis will be used to provide a comparison of actual bridge performance versus suggested traditional analysis. The results of this study show that the load carrying capacity is higher than what is calculated using traditional rating methods. Consequently, load posting could be removed for the analyzed bridge. This conclusion may be applicable to similar movable bridges but will have to be confirmed with a procedure similar to the one presented in this research.