Study On Direct Shear Performance Of Dry Joints Of PCSB Beam Under Multiple Factors

Nowadays,the short-line match-casting method is often adopted to manufacture the segmental beams in the prefabrication process,but there are also many problems in this method,such as moving the segmental beams section repeatedly and adjusting the templates.Besides,it is necessary to establish a wire control network and level control network in the prefabrication plant to carry out a three-dimensional linear control,so as to adjust and correct the alignment of precast concrete segmental bridges.In order to overcome the shortcoming of match-casting method,a novel joint structure is proposed for match-casting-free construction.The match-casting-free construction is managaed by setting a gap between the shear key and the shear groove along the dry joint.The shear key is smaller than the corresponding shear groove,which can satisfy the matching error when assembled,and the concrete beam segments can be manufactured independently.The shear key is a necessary structure in the joints of precast concrete segmental bridges.In this paper,it puts emphasis on the performance of the match-casting-free dry joint,including the shear failure mechanism,the friction coefficient of the initial and residual resistance,the supporting capacity of shear key,and shear strength reduction.In the tests,the shear capacity of the gap joint reduced by 17.75%-42.43%because of the influence of partial restraint and contacting position.The influence of the contacting position at bottom,gap height and base height of shear key on strength reduction was analyzed by numerical simulation.The shear capacity of full contact was higher than that of partial contact according to the results,while the integrity of shear key was easily damaged in the case of left contact,resulting in a significant strength reduction.The force distribution in the bridge would vary when the unfavorable factors such as vehicle load,wind load and earthquake are applied.Segmental beams made by high-performance concrete could be used at the dangerous section to resist shear force.Segmental beam manufactured with different types of concrete is possible via match-casting-free method.In this paper,the shear performance of composite joints composed of different concretes was studied.The stress zone of composite joints could be categorized into fracture zone,shear zone,as well as crushing zone according to the test results.The stress that transferred to the shear groove exceeding the compressive strength of the shear groove.Consequently,it caused the crushing phenomenon of the shear groove of the composite joint,and it was confirmed by the finite element analysis on stress distribution.From the perspective of the shear capacity of composite joints,the peak shear load of specimens with steel fibers increased by more than 20% than those without steel fibers.Although the problems such as aligment and interface contact exsited in the match-casting-free dry joints,it is believed that match-casting-free construction method would be available if more researches on the shear behavior of the match-casting-free structures are carried out in the future.