Research On Joint Construction And Mechanical Behavior Of Assembly Bridge Panel Of Steel-concrete Composite Structure

As the main part of precast concrete bridge panel site construction,wet joints has became the most vulnerable part to disease for its complex loading,unclear power transmission path?This paper study on the bending performance of UHPC wet joints under positive bending moment and negative bending moment as to stress characteristics of different area of the bridge panel.Later poured concrete shrinkage function is analyzed by simulation to analyze the joint interface stress distribution,and based on the pull rod model,considering the UHPC juncture area of longitudinal reinforcement discontinuous mechanical characteristics,puts forward the UHPC plate formula of ultimate bearing capacity with seam.The main conclusions are as follows:(1)A new interface treatment for improving the mechanical properties of joints.For the ways to deal with juncture interface including dabbing and water jetting causing uneven interface roughness and big workload.This paper puts forward a new type of way to deal with interface by sticking steel wire front template to improve the joint crack resistance.Through the experiment,the rationality of the rough handling method proposed in this paper is verified,and it is found that this method can increase the initial crack stress of UHPC by 1.5mpa.(2)Experimental test on bending performance of UHPC wet joints under positive bending moment.Through the 24 UHPC board under bending load test,we studied the parameters including prestress level,precast slab interface treatment,ratio of concrete,longitudinal reinforcement lap form which affecting flexural bearing capacity of the structure,deformation,failure mode and the influence of the joint force.The results show that the application of UHPC in the joints can make the concrete slab have the typical multi-seam cracking phenomenon,and improve the bending performance of the joints effectively.The prestress can improve the initial crack stress and UHPC board bearing capacity effectively.The prestress level of 5MPa or 3MPa is applied to the test piece,and the initial crack stress can be increased by 7MPa or 4MPa.At the same time,the initial crack stress can be effectively improved by rough treatment of the precast panel interface.By the proposed interface processing method(braided steel mesh fitting template),the initial crack stress at the joints increased by at least 1.5mpa,and the typical multi-seam cracking occurred in UHPC board.The "U" form joint method can effectively reduce the length of the longitudinal rib and shorten the width of the wet seam.After changing the mixture ratio of UHPC materials(adding coarse aggregate),the effect of the initial crack stress on the structural joints was less than 0.1MPa,and the ultimate bearing capacity of UHPC board was less than 5k N.(3)Experimental test on bending performance of UHPC wet joints under negative bending moment.Through the load test of 10 UHPC boards with negative bending moment,the influence of the research parameters on the performance and failure mode of UHPC wet joints was compared and analyzed under different loads.The results show that the loading form influences the initial crack stress,compared with form of positive bending moment,and the negative bending moment is increased by 1.25 MPa.Precast plate interface processing and prestress also improve the initial crack stress and affect the failure mode of UHPC board.According to the ductility evaluation method of UHPC board,the deformation capacity of the specimen under negative bending moment is small,and the ductility coefficient is 1.5 under the positive bending moment.(4)Calculation method on bending strength of concrete jointsThe calculation method of flexural capacity of UHPC board is obtained by analyzing the bending process of UHPC board.Based on the strut-and-tie model,considering discrete features of "U" shape lap reinforced in seams area,proposed a formula of ultimate bearing capacity on seam of UHPC plate bending,which can better explain the "U" shape steel lap joint "circuitous power flow transfer mechanism,and compares with the joint test data.By analyzing the stress characteristics of the tongueand-groove at the joints,the mechanism of the initial crack stress contribution of the comb teeth is explained.