Assessment and Risk Ranking of Conventionally Reinforced Concrete Bridges for Shear

Abstract

Large numbers of conventionally reinforced concrete bridges remaining in service are lightly reinforced for shear. State-of-the-art assessment of these bridges for shear requires consideration of shear and moment interaction. An assessment and risk-ranking methodology is proposed that incorporates moment–shear interaction. From analyses of vehicle loads on indeterminate bridge models, maximum moment and maximum shear are not coincident at intermediate support locations. Determining the critical combination of shear and moment requires evaluation of envelope values from shear–moment load histories for comparison with capacity curves. Capacity of the sections is determined by using AASHTO modified compression field theory, and statistical understrength is based on experimental test results. Comparison of the load effects and capacity is demonstrated for an in-service bridge to determine the reliability index (measure of relative risk) at sections along a girder. The reliability index can be used to establish rational load restrictions on the basis of a target reliability index for the inventory. The index can also be used for comparison between components and populations of conventionally reinforced concrete bridges for risk ranking. Ranking based on relative reliability indexes permits bridge engineers and managers to prioritize the bridges for repair or replacement.

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