INVESTIGATION OF COMPOSITE ACTION IN BRIDGES BUILT WITH ADJACENT PRECAST INVERTED T-BEAMS AND CAST-IN-PLACE TOPPING

ABSTRACT Short to medium span composite bridges constructed with adjacent precast inverted T-beams and cast-in-place topping are intended to provide a higher degree of resiliency against reflective cracking and time dependent effects compared to voided slab and adjacent box girder systems. This paper investigates the composite action between the unique precast and cast-in-place element shapes. A full-scale composite beam has been tested under different loading arrangements with the purpose of simulating the service level design moment, strength level design shear, strength level design moment and nominal moment capacity. To investigate the necessity of extended stirrups one half of the span featured extended stirrups whereas the other half featured no extended stirrups. It is shown that the system behaved compositely at all loading levels and that no slip occurred at the interface. In addition to measuring slip at various interface locations full composite action has been verified by comparing load displacement curves obtained analytically and experimentally. It is concluded that because of the large contact surface between the precast and cast-in-place elements, cohesion alone appears to provide the necessary horizontal shear strength to ensure full composite action.