Crack Control of Negative Moment Regions in Continuous Composite Box-Girder Bridges with Precast Decks by External Prestress

In a continuous composite bridge with precast decks, tensile stress in a maximum negative moment region under service loads should be controlled. For ensuring the crack prevention at transverse joints, prestressing by internal tendons in all spans is not efficient. A stress distribution of concrete slab by internal tendons is complex due to several construction steps, shear pockets and prestress losses by long-term behavior. Therefore in the negative moment regions, additional prestressing method after shear connection is needed. In this paper, static tests on a two span continuous composite bridge with precast deck, which was prestressed additionally by external tendons near an interior support, were conducted and effects of the prestressing by external tendons were observed. Through analyses for a designed continuous composite bridge, applicable prestressing method for composite bridges with precast decks was proposed.