Evaluation and load rating of an aging and impact damaged steel girder bridge: case study

One of the common reasons for traffic disruptions and costly repairs or replacements of highway bridges is impact damage from inadequate vertical clearance or over-height vehicles. The current study diagnosed, and load rated an old impact-damaged non-composite steel girder bridge on IH-30 in Dallas, TX, with extensive deck delamination. Load testing and Non-Destructive Evaluation (NDE) employing Ground Penetrating Radar (GPR) and Impact Echo (IE) were used to evaluate the six-span bridge. Span one was simply supported, while the others were continuous. The IE scan of the deck surface revealed that approximately 40% of the concrete was severely delaminated. While the GPR scans indicated that the top rebar covers in the cast-in-place deck ranged from 38 to 64 mm for 62% of the deck area. Analysis of strain data from the load test showed that the girder neutral axes were in the web, demonstrating non-composite action between the deck and girders. An innovative approach was employed to load rate the deck and the girders by combining the NDE and load testing results following AASHTO procedures. Since the girders and the deck were unsafe for HS-20 loading per the Texas Department of Transportation's requirements, load posting, and urgent bridge rehabilitation were recommended.