Experimental Study On The Shear Resistance Of The Interface Between Grooved UHPC Precast Beam And Cast-In-Place Concrete Bridge Deck

As a kind of advanced cement-based composite material,ultra-high performance concrete(UHPC)is popularized and applied in civil engineering with its excellent mechanical properties and durability.The combined beam structure(UHPC-NC beam)using UHPC prefabricated beams and cast-in-place ordinary concrete bridge decks has the characteristics of increasing the span,reducing the weight of the bridge,and speeding up the construction.It has been applied in bridge engineering.However,there are few studies on the shear connection between UHPC-NC beams,and the understanding of the shear performance of UHPC structural nodes is still very limited.Therefore,it is of great application value to test and theoretically study the shear performance of UHPC structural nodes.In this paper,the shear resistance of the interface between the prefabricated UHPC beam and the cast-in-situ bridge deck was taken as the research object.27 specimens were produced,including 9 specimens without shear reinforcement and 18 specimens with shear reinforcement.Taking cast-in-situ bridge deck type(UHPC,NC,LC),shear reinforcement ratio(1.70%,2.31%,3.01%)and interface treatment(groove interface,smooth interface)as test variables,the launch test is used to explore Its effect on the shear resistance of composite beam interface.During the test,the external load,vertical slip,lateral cracking displacement and steel bar strain gauge data were recorded.The failure mechanism of the composite beam specimen under load was analyzed based on the failure mode,ultimate load,residual load,load displacement response and load steel bar strain curve.,The key factors affecting the shear resistance of composite beam interface are discussed.In this paper,by comparing the test results with the calculated values of the specifications,it is found that the calculation formulas of the shear capacity of the AASHTO LRFD 2015 and ACI 318-14 specifications are difficult to accurately predict the shear resistance of the groove interface.Therefore,based on the test results,the author uses the method of multiple regression analysis to obtain the revised formulas for the AASHTO and ACI specifications,which can well predict the experimental research results of this article.This article mainly draws the following conclusions:(1)UHPC-UHPC combined specimens have higher shear bearing capacity than UHPCNC and UHPC-LC combined specimens.Although the prefabricated beam is UHPC,the castin-place bridge deck is controlled by NC and LC with lower strength The shear resistance of the corresponding test piece;(2)Shear steel bars almost yield when the specimen reaches the limit load or before,which is in line with the classical assumption of shear friction theory,and the yield strength of the steel bar can be used for the calculation of the shear bearing capacity.The shear reinforcement plays an important role in the ultimate load of the specimen and dominates the residual load.There is an optimal range for the reinforcement ratio of shear steel bars.After exceeding,continue to increase the reinforcement ratio,which has a limited effect on improving the shear bearing capacity;(3)Compared with the smooth interface test piece,the groove treated test piece obtains higher shear bearing capacity,which is an effective way to improve the shear resistance of the interface between the UHPC beam and other concrete cast-in-place bridge deck.