Flexural load-rating of slab-on-girder bridges by nonlinear proxy finite-element analysis

The proxy finite-element analysis (PFEA) technique is significantly extended to improve its utility and its predictions of bridge ultimate capacity are verified. Refinements and extensions to the method include a substantial reduction in up-front computational effort, explicit consideration of the effects of skewness on bridge behavior, and expansion of the technique's mechanics formulation to include the effects of prestressing. PFEA's prediction of ultimate flexural capacity is verified by simulating the capacity of a previously conducted, full-scale destructive test of a prestressed concrete girder bridge with good prediction of recorded load-deflection data. Live-load testing (LLT) of five, skewed, reinforced concrete bridges is described. The tested bridges are then load-rated by PFEA, leading to average increase in rating factor exceeding 120%, as compared with an average increase of 34.9% with LLT. This demonstrates that PFEA's consideration of material nonlinearity leads to larger increases in predicted capacity while retaining the conservative assumptions required by design and analysis codes. Practical usage and implementation of PFEA are addressed, including application to ratings and permitting.