Load Test and Transverse Analysis of a Precast Segmental Concrete Box Girder Bridge

The Seabreeze Bridge, a single cell precast post-tensioned concrete segmental box girder located in Daytona Beach, Florida, was instrumented and tested to determine the effects of truck live load. Strain gages were installed on the interior and exterior of the box girder to quantify transverse response. The measured strains were compared to predictions from a transverse analysis commonly employed by segmental bridge designers, where a two-dimensional frame model is combined with plate influence surfaces to calculate transverse bending moments in the cantilevers, webs, and bottom slab. Measured strains were found to be up to 90% smaller than the frame predictions. Strains in the top slab and cantilever were predicted with the highest accuracy indicating more force spreading than is assumed by the frame analysis. Cantilever transverse strains were found to be 60% higher near midspan than near a pier. It is hypothesized that the traffic barrier is stiffer near the pier and carries a greater share of the cantilever live load when compared to the midspan cross-section. Recommendations are made to improve prediction accuracy of the simplified frame model, including the addition of springs at supports to model distortion and on the wing to model the barrier as well as increasing the longitudinal depth of the model near the bottom of the cross section.