Experimental Research On Mechanical Properties Of Prefabricated Concrete Bonding Surface And Composite Beams

With the idea of green building,the process of building industrialization has entered the era of rapid development in today's construction industry.The prefabricated concrete structure is one of the main structural forms of building industrialization.Prefabricated concrete composite member is also made from a mix of precast concrete sections and post-pouring joint components,which is formed by pouring concrete on the precast concrete parts casting layer.Whether the precast part and the post-pouring part of prefabricated concrete composite component can work together mainly depends on the bonding performance of the bonding surface.In prefabricated concrete structure,laminated beam is one of the main horizontal components of the building,and the mechanical performance of the composite beam plays an important role in the overall performance of the floor structure.According to relevant regulations,the stirrup should be stretched out when making the precast part,which will cause the installation trouble of the longitudinal reinforcement in the post pouring concrete.Therefore,to promote the prefabricated concrete structure,it is necessary to carry out an in-depth study on the mechanical properties of the bonding performance of the prefabricated concrete and the mechanical properties of the composite beam with the stirrups-overlapping hoops.In this paper,the mechanical properties of bonding surface of precast and post-cast concrete are first studied in two aspects:static load and dynamic impact load.Then it puts forward the new form of stirrups-overlapping hoops by referring to relevant regulations and information both at home and abroad,and studies the bending performance of the composite beams with the stirrups-overlapping hoops under monotonic static load through tests.ABAQUS finite element software was used to simulate each test piece beam,and the test results were compared and analyzed.Through theory,experiment and numerical analysis,the mechanical properties of prefabricated concrete bonding surface and composite beam with the stirrups-overlapping hoops are studied systematically.The main research and its results are as follows:(1)Experimental study on the adhesive splitting tensile and bending performance of post concrete on post pouring concrete was conducted.Combined with analysis of variance,it investigated the effects of these factors as caking casting method,bonding surface roughness,post pouring concrete strength grade,temperature and cooling ways.(2)Variable cross-section steel ?74mm SHPB device is used to test the dynamic splitting tensile performance of post pouring concrete on precast concrete and study its influence and variation law of different bond surface roughness types(type A,B and C)and different strain rates(28s-1,46s-1 and 69s-1),which provide experimental basis for the application of prefabricated concrete structure.(3)The bending performance test of the new fabricated composite beam with the stirrups-overlapping hoops and the ordinary composite beam and the cast-in-place beam was carried out,describing in detail the test phenomena,crack development and failure mode of the specimens under the bending moment load,and obtaining the curve of load-strain of concrete and steel in the key position.The failure modes of each specimen are divided into elastic stage,yield stage and failure stage.Test process and phenomena of the four specimens in each stage are of high similarity.(4)Based on the test results,the bearing capacity,displacement ductility,steel bar strain,crack and bending stiffness of the new fabricated composite beam with the stirrups-overlapping hoops and the ordinary composite beam and the cast-in-place beam were comparatively analyzed.In addition,the design proposal and construction requirements of the composite beam with double hook and J-type stirrups-overlapping hoops were put forward.(5)By means of large general finite element software ABAQUS,the prefabricated concrete composite beam model was established under the form of special casting.The stress and strain in the concrete,longitudinal reinforcement stress,stirrup stress,deflection components,bearing capacity were analyzed by simulation,which summarized the change law of the conclusion and provided a reference for engineering practice.