Demonstration and examination of a procedure for successively improved structural assessment of concrete bridges

Abstract

AbstractAssessing the load‐carrying capacity of existing bridges is an important infrastructure management task. In order to support the structural assessment of concrete bridges better, a procedure has been proposed, based on successively improving the bridge analysis. A multilevel strategy for structural analysis has been combined with concepts for verification of the desired safety margin, thus providing tools for engineers to model the structural behavior of bridges more accurately when necessary. This paper describes the procedure as applied to a prestressed concrete girder bridge, with use of experiences from the previous failure tests and associated evaluations of the bridge. Initial structural assessment indicated the critical failure mode to be due to shear in one of the girders; however, the enhanced analysis showed a complex failure involving both the girder and the bridge deck slab. Improving the structural analysis using nonlinear FE analysis for the loading initially identified as critical, increased the permitted axle loads on the bridge to 12 to 14 times those given by traditional and standardized assessment methods, depending on the concept used for safety verification. The model uncertainty was crucial for the verification of the structural safety and has to be properly taken into account. However, there are few recommendations, with regard to model uncertainties, on the application of nonlinear FE analysis, and detailed guidelines should be used for the modeling procedure in order to reduce analyst‐dependent variability in the results. The presented study demonstrates the applicability and the advantages of using the proposed procedure for successively improved analysis for bridge assessment.