Date of this Version
Cast-in-place bridge decks are known to have transverse cracking early in the life of the bridge due to shrinkage and temperature effects. The cracks result from immediate composite behavior between the girder and the deck. For steel bridges, this bond is caused by shear studs welded to the steel beams and embedded in the cast-in-place deck. Prevention or closure of these cracks could greatly increase the durability of the bridge.
The following research focuses on introducing a system that will have delayed composite action, allowing strain in the concrete before it becomes composite with the girder. The system is meant to reduce or eliminate transverse cracks before behaving as a fully composite section. Additionally, post-tensioning is used to put compressive strain on the concrete deck before bonding to the shear studs in order to prevent cracking once composite behavior is achieved.
The results of this research prove to be promising. In addition to small scale development and testing of the delayed composite action (DCA) with post-tensioning (PT) system, a full scale system was constructed and tested. The DCA beam showed no cracks due to shrinkage or temperature effects, in addition to more movement relative to the girder before bond to the shear studs. The moment capacity of the DCA with PTsystem equaled the specimen with identical parameters minus the DCA and PT. This shows that full composite behavior was achieved in addition to reduced cracking due to immediate composite behavior.
Advisors: Maher K Tadros