Integrated Bridge Load Rating Allowing Rational Assessment of Foundation Reuse

Abstract

Reuse of existing bridge foundations has been gaining momentum and acceptance among practitioners in the last few years. Proper characterization of the bridge foundation (embedment, load-carrying capacity, etc.) is necessary for bridge reuse when the original design conditions are changed because of scour, bridge widening, increased loading, or other changes to the structure. This paper presents rational means to analyze existing foundations using a hybrid analytical-numerical method so that reuse can be optimized. An integrated bridge load rating that considers the entire superstructure-substructure system can be established using the proposed method. Performing a quantitative integrated bridge load-rating analysis that considers geotechnical issues and soil-structure interaction for a substructure is essential to prevent functional or catastrophic failure under a live load. A reliable determination of the unknown pile embedment is also a prerequisite for a realistic integrated bridge load rating. The design criteria used when the bridge was originally constructed are important factors in the load rating process. Costly detours, repairs, replacement, or loss of life could be associated with inaccurate embedment estimates or use of criteria incongruous with the original design. The results of case histories show the importance of a realistic assessment of the pile embedment and of using appropriate geotechnical and structural design criteria when calculating the integrated load rating of bridges to advance the consideration of foundation reuse.