EFFECT OF STRANDS DEBONDING ON THE STRUCTURAL PERFORMANCE OF PRECAST PRETENSIONED BRIDGE GIRDERS

This paper summarizes an experimental investigation regarding the effects of strand debonding on the flexure and shear behavior of simply supported precast pretensioned bridge members composite with a cast-in-place deck slab.  Five specimen sets were fabricated and tested to failure as simply supported members under a single concentrated load. Four specimen sets consisted of Type-I AASHTO girders composite with a cast-in-place deck slab. One specimen set consisted of Indiana State Type CB-27 box girders also composite with a cast-in-place deck slab. Each specimen set consisted of two identical beams with different strand debonding schemes near the ends. In each set, one beam had the strands bonded throughout the entire length. The other one had some percentage of the strands debonded near the ends.  The current ACI/AASHTO requirements for flexure and shear design of pretensioned bridge girders with debonded strands were examined. The Current ACI/AASHTO equation for the evaluation of web-shear cracking capacity of composite prestressed concrete beams gave conservative estimates of the web-shear cracking loads of both the fully bonded and the debonded I-beams. Slightly unconservative results were obtained for the test values of the box girders. Findings of this study indicate that current ACI/AASHTO requirements for strand development length are not adequate.