Monitoring Of An Interstate 25 High Performance Concrete Bridge With An Embedded Optical Fiber Sensor System

The I-25/Dona Ana Interchange in Las Cruces NM is a simple span, high performance concrete (HPC)prestressed girder bridge. The girders are six prestressed, BT-63 HPC girders with a span length of 112.5 ft (34.2 m). The bridge was monitored from fabrication through service with an embedded optical fiber sensor system. Thirty two Fiber Bragg Grating (FBG) optical fiber deformation sensors were installed in the beams during fabrication. The strands were 6/10 inch ( 1.5 cm ) low relaxation strands and the concrete had a design compressive strength of 8 ksi (55.2 MPa) at release and 9.5 ksi (66.5 MPa) at 28 days. The bridge was monitored for two years, from transfer of the prestressing force through service. Several topics that are studied in this project: prestress losses, camber, shear and moment girder distribution factors, impact factor, insitu material properties and serviceability under traffic loads. The results from sensor measurements were compared to the values predicted by the AASTHO codes and other design codes or empirical equations, to check the accuracy of these codes when applied to HPC girder bridges.