Experimental Study On The Mechanical Properties Of Concrete Beams Welded With New Steel Casing

At present,the connection mode of assembled structure node mainly includes two ways: dry connection and wet connection.Because of its simple structure and convenient operation in construction,wet connection is the mainstream connection in China.However,the wet joint has the problems of insufficient research or development and high cost of the casing and grouting material.In addition,due to the shortage of domestic workers' skills and quality,the field detection of the casing grouting joint and the constrained grouting anchor joint is difficult.Compared with the wet connection,the dry connection has the advantages of greatly reducing the construction period,reducing the field wet operation,less environmental pollution and intuitive operation.In order to further improve the performance research of the dry joint,this paper studies the welded joint in the dry joint,and studies the mechanical properties of the welded joint specimen of the rebar casing and the mechanical properties of the welded joint in the concrete beam.Main research contents and results are as follows:(1)Four influencing factors were considered in the test of the welded joint of the steel casing,that is,the length of the weld,the welding form,the strength of the electrode,and the diameter of the reinforcement.48 welded joints were designed and the welded joints of the reinforcement joint were tested.Unidirectional tensile test.According to the test results of the ultimate bearing capacity and load-displacement curve of the welded specimen of the steel casing,a parametric analysis of the factors affecting the mechanical properties of the welded specimen of the steel casing is performed.The test results show that: the use of 10 times the diameter of the weld seam and the double-seam welding form can reduce the possibility of shear damage between the casing and the weld;the selection of 16 mm diameter reinforcement can effectively improve the strength of the steel casing welding test piece Ultimate bearing capacity.Combined with the shear resistance formula of the weld,through the three factors of the length of the weld,the height of the weld,and the strength of the electrode,the minimum design length of the weld to prevent the shear damage of the welded joint of the single-seam test piece of the steel casing is given.(2)Three concrete beams were produced,including a cast-in-place concrete simply-supported beam,a cast-in-place concrete simply-supported beam welded with a steel casing at the bottom,and a cast-in-place concrete welded with two steel casings at the bottom Simply supported beam.Through the three-point loading,the research on the bending performance was carried out,the rules of crack distribution and failure morphology were analyzed,and the bearing capacity,deformation and other indicators of the test pieces were tested.Compared.The test results show that the failure form of concrete beams welded by steel casing welding is similar to that of cast-in-place concrete beams;its cracking load and crack width meet the requirements of the current code;the requirements of the current code are not suitable for calculating its ultimate bearing capacity.This article revises the current standard formula;the mid-span deflection of the welded connection of the steel casing to the bent beam is too large,it is recommended to control the number of welded joints of the steel casing in the actual project.(3)Establish the relevant concrete beam finite element model through ABAQUS software,calculate the ultimate bearing capacity and mid-span deflection of each test beam,and compare it with the experimental data.The results show that: the finite element analysis results and test results in this paper are basically According to the agreement,the maximum numerical error is about 10%,which verifies that the model is accurate.