In-Service Shear and Moment Girder Distribution Factors in Simple-Span Prestressed Concrete Girder Bridge

An optical fiber monitoring system was designed and built into the I-25 bridge at the Dona Ana exit in Las Cruces, New Mexico. The bridge is a simple-span, high-performance prestressed concrete girder bridge. The girders are six BT-63 high-performance-concrete girders with a span length of 112.5 ft (34.2 m). Fiber Bragg grating optical fiber deformation sensors along with thermocouples were embedded in the girders during fabrication. Sensors were installed along the top and bottom flanges and at midspan and quarter spans. Pairs of crossed sensors in a rosette configuration were embedded in the webs at the supports. The bridge was monitored for 2 years, from transfer of the prestressing force through service. The sensor data were analyzed to evaluate shear and moment girder distribution factors, in situ material properties, pre-stress losses, camber, dynamic load allowance, and bridge performance under traffic loads. This study focuses on the lateral load distribution in the bridge. Shear and moment girder distribution factors are obtained from a finite element model, sensor measurements under a live load test, as well as regular traffic loading and compared with the values specified by the AASHTO standard specifications (2002) and the AASHTO load and resistance factor design specifications (2007).