Reliability-Based PC Bridge Girder Rating Model with Integrated Diaphragm Effect

Abstract

A reliability-based rating model for prestressed concrete (PC) bridges that allows the inclusion of integral intermediate diaphragms was developed. The model incorporated the primary uncertainties in stiffness parameters affecting diaphragm effectiveness. The approach was evaluated using a live load model developed using weigh-in-motion data from Michigan. It was found that using the diaphragm model can significantly increase girder reliability in some cases, increasing the reliability index from a baseline of 2.5 to 3.2, as well as from a baseline of 1.5 to 2.1 for the most effective case considered. Across all bridge geometries considered, the corresponding increase in rating factor was found to range from 3% to 13%. Alternatively, including the model potentially allowed up to approximately 5%–8% losses in girder capacity or increases in vehicular live load from 7% to 12% without reductions in the rating factor. Use of the model may provide significant benefits for some structures, minimizing unnecessary traffic restriction while maintaining the required levels of reliability.