Precast concrete deck-to-girder connection using Ultra-High Performance Concrete (UHPC) shear pockets

摘要

Precast concrete deck systems have been successfully used in Accelerated Bridge Construction (ABC). In most systems, precast concrete deck-to-girder connections use special shear connectors embedded in the girders and projecting into the deck block-outs (pockets or troughs) that are grouted to achieve composite sections. This requires tight production/erection tolerances that complicate deck and girder fabrication and compromises the economics of the precast concrete deck systems. In this paper, a new deck-to-girder connection is developed using ultra-high performance concrete (UHPC) to relax production/erection tolerances for both precast deck panels and girders. Typical girder shear reinforcement remains unchanged but terminated in the haunch below the soffit of deck panels to eliminate any conflict with the deck shear pockets. Loop bars are installed in the shear pockets that are filled with UHPC to provide required interface shear capacity while relaxing production/erection tolerances. Small scale push-off and double shear tests were conducted to evaluate the interface shear resistance of the connection. Full-scale push-off specimens are fabricated and tested to evaluate the structural performance and constructability of the proposed connection. Test results indicated that interface shear resistance of the connection can be predicted using the AASHTO LRFD shear friction model with different cohesion and friction factors that are dependent on the UHPC compressive strength. Also, UHPC fiber stability has a significant effect on the capacity of the proposed connection. Design example and design aids are presented to demonstrate the design of the new connection in a typical bridge.