Experimental study and analysis of a full-scale CFRP/CFCC double-tee bridge beam

This paper presents a study on the fabrication, instrumentation, and flexural testing of a full-scale double-tee (DT) beam, prestressed using bonded pretensioned CFRP Leadline(TM) tendons and unbonded carbon fiber composite cable (CFCC) post-tensioning strands. The beam was designed to simulate the performance of the DT beams used for the construction of the three-span Bridge Street Bridge, the first vehicular concrete bridge ever built in the United States that uses CFRP material as the principal structural reinforcement. Testing focused on measurement of strain distributions along the length and depth of the beam, transfer length, camber/deflection, cracking load, forces in post-tensioning strands, ultimate load-carrying capacity, and mode of failure. In addition, an analysis approach is presented to theoretically evaluate the response of the tested beam. It was observed that the ultimate failure of the beam was initiated by partial separation between the topping and the beam flange, which led to the crushing of the concrete topping followed by rupture of bottom tendons. The tested beam was found to have significant reserve strength beyond the service load. Theoretical calculations are similar in value to the corresponding experimental results - especially under the service load condition.