CIVIL ENGINEERING 365 ALL ABOUT CIVIL ENGINEERING



AbstractLoad-posted bridges have potential effects on traffic, commerce, and emergency egress due to detours in routes between origins and destinations. Posted bridges can also be problematic for state departments of transportation from a management standpoint because they may call for more frequent maintenance, monitoring, and inspection. For these reasons, it is beneficial for states to minimize the number of load-posted bridges. This study investigates a continuous steel plate girder bridge superstructure and proposes a methodology for exploring the refined load rating of this bridge type in a safe manner through refined modeling and load testing. Load test results were used to examine live load distribution factors, and finite-element models were developed to refine load ratings. It was determined that the refined load-rating factors for the bridge are significantly higher than the currently posted limits, and therefore, the posting could be removed. The methodology presented in this paper can potentially be used to increase the load-rating factors for similar continuous steel girder bridges.Practical ApplicationsThe results of this case study suggest that some continuous steel girder bridges that were designed as noncomposite without shear studs may have unaccounted reserve capacity that can increase their load ratings. For a specific bridge or a group of the same type of load-posted bridges, refined analysis methods can be used to improve the load rating or potentially even remove the posting. Live load distribution factors may be determined through refined analysis to provide a more accurate estimate of the load distribution among girders. In addition, for certain bridges that are designed as noncomposite, the level of partial composite action can be determined through nondestructive load testing. Naturally, these refined analysis methods require more time and effort than a basic load rating analysis. However, the results could create a more manageable inventory for bridge owners and allow more trucks to use bridges currently posted for load, providing economic benefits.



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