Research On The Connection Performance Of Composite Beam In Prefabricated Concrete Structure

With technical advantages such as energy conservation,green environmental protection,and short construction period,Prefabricated buildings have been became a mainstream construction method in developed countries,especially in developed countries such as the United States,Japan,and Canada.In recent years,with the country's emphasis on the development of prefabricated buildings,the concept of green building has been proposed.At present,the existing integrated monolithic concrete building structures in china,structural splitting methods using "superposed beams," superposed floor slabs,precast columns or cast-in-place columns,and cast-in-place nodes "are more common.In the background of the China's current social,prefabricated building structural codes are gradually established in practice,and most of them are based on the concept of "equivalent cast-in-place",which directly or indirectly draws on some points of the cast-in-place structural code to stipulate the prefabricated buildings should follow Design and construction requirements.At present,for the construction method of superposed beams,the recommended practice in China's industry standard "Technical Regulations for Assembled Concrete Structures"(JGJ1-2014)is to require the thickness of the superposed layer of the superposed beam used as the main beam.When it is less than 150 mm,a notched cross-section prefabricated beam should be used,and the thickness of the notch side is not less than 60 mm,and the depth of the notch is not less than 50 mm,and the sum of the depth of the notch and the thickness of the laminated plate is not less than 150 mm.According to the actual situation reflected by the component processing plant,The notch edge of the above-mentioned notch superposed beam is inconvenient during the production due to the small beam width during the prefabrication.In order to improve the efficiency of the production,a part of the structure is constructed.The processing plant adopts the practice of not making a notch even if the thickness of the precast beam overlap layer does not satisfy more than 150 mm.Although some component processing plants show that the performance indicators of non-notched precast beams meet the requirements,there are fewer reports about the relevant tests and theoretical studies.It isalso difficult to deduce the quantitative influence of notches on the static and seismic performance of prefabricated beams from assembled industry standards.To vigorously promote the use of such non-notched laminated beams in practical engineering,it is necessary to make an in-depth study on the mechanical properties of recessed and non-grooved composite beams for prefabricated building concrete structures.In this paper,a full-scale shear and flexural static performance test of 21 test beams is carried out on the prefabricated composite beam members of a prefabricated construction project under construction to study the notched and non-grooved pairs of prefabricated composites which was the impact of the mechanical properties of the beam,and I hope to verify the applicability of the notched prefabricated composite beam,and to provide a test basis and theoretical basis for finding a process improvement method for the prefabricated composite beam structure suitable for the production habits of existing prefabricated component processing enterprises in China..The main research work and results are as follows these:(1)In the test,the normal strain of the concrete surface and the cast-in-situ beam on the concrete beam with the grooved laminated beam and the non-grooved laminated test beam conformed to the flat section assumption,and the crack development and failure patterns were not significant.difference.(2)The measured shear and bending capacity of the laminated layer using grooved and non-grooved composite beams is greater than the theoretical value.The grooved and non-grooved composite beams have no obvious shear and bending capacity.The difference is in good agreement with the bearing capacity of the cast-in-place beam.The shear and bending bearing capacity of the composite beam has a certain margin calculated according to the "Specifications for the Design of Concrete Structures"(GB50010-2010),and the calculation results are biased to safety.(3)Through the shear and bending tests,the comprehensive analysis of the failure morphology,the measured bearing capacity and theoretical values,the ductility coefficient,and the short-term stiffness before and after cracking of the laminated beams with groovesand non-grooves is obtained.The existence of grooves in the laminated layer will not significantly affect the normal static mechanical properties of the laminated beam.There is no significant difference in the mechanical properties of the grooved and non-grooved laminated beams and the cast-in-place beams.(4)By using the finite element ABAQUS software of the simulation modeling analysis,the simulation results agree well with the experimental data.Through the comparison and the analysis,there is no significant difference in the static performance of the laminated beams with grooves and non-grooves,which are equivalent to the mechanical properties of cast-in-place beams.(5)It is recommended that when the groove of the fabricated laminated beam overlap layer is not easy to construct,a non-groove overlapping surface can be used instead of the groove overlapping surface to facilitate construction,and a supporting role can be taken during construction,and Measures are taken to ensure that the non-grooved superposed surface has a certain degree of roughness to ensure good bonding performance of the superposed surface,thereby ensuring the overall force of the precast concrete and the post-cast concrete.