Experimental Study On The Shear Behavior Of Joint Filled With High Performance Concrete In Precast Hollow Slab Beams

Precast hollow slab bridges are widely used in engineering because of their simple structure,good performance,low building height,and prefabrication.However,precast hollow slab bridges often exist problems such as longitudinal cracking of bridge deck pavement,cracking and falling off of the shear key joint.The failure of the shear key joint will cause longitudinal cracks in the bridge deck.Rainwater and harmful substances will penetrate into precast hollow slab bridges along the longitudinal crack,which will affect the durability of precast hollow slab bridges.For precast hollow slab bridges,the shear key joint is an important structure for load transmission.Its damage weakens the transverse connection,which seriously affects the overall performance of the superstructure of precast hollow slab bridge.With the development of new concrete materials,such as self-compacting concrete and ultra-high performance concrete(UHPC),their excellent material properties are of great significance for solving the problem of the shear key joint cracking,and play an important role in the optimization and improvement of the shear key joint.The shear key joint mainly bears and transmits the transverse shear force generated by the vehicle load,and the excessive lateral shear force is also an important cause of the shear key joint damage.Therefore,it is of great significance to study the mechanism of shear failure of filled new self-compacting concrete and UHPC.At present,there is a lack of experimental research on shear key joint about high-performance concrete.This study considers a new type of shear key joint introduced by the Federal Highway Administration(FHWA)in 2014 by comparing the shear performance of different types of joint structures at home and abroad.Through the test method to study the shear performance of the new type of shear key joint,it can provide some suggestions for the treatment of existing bridge disease and the design of new bridge.The principal study are as follows:(1)The preliminary experiment mainly research on the shear resistance of UHPC shear key joint and joint's interface,to exploring their failure mechanism and comparing their differences in failure modes and shear performance.(2)On the basis of the preliminary experiment,the experimental parameters mainly include interface type,concrete type and strength of shear key joint,the type of reinforcement structure,and the diameter of reinforcement.For the purposes,fourteen beams with shear key joint and one monolithic beam was tested.The failure mode,shear stiffness,cracking load and ultimate load of the test beams were analyzed,and the effect of the above experimental parameters on the shear behavior of the testing beams was summarized.(3)Based on the failure mode of the test beam and the hypothesisthe of homogeneous elastic beam,the suggested formula for the shear key joint design is proposed.The formula is certified by comparing the experimental value with the calculated one.The proposed formula for design can accurately predict the shear capacity of the shear key joint.