Measurement And Analysis Of Residual Stress Of Stud Welding In Steel Plate Concrete Composite Structures

As the most widely used shear connector in steel plate concrete composite structure,stud is connected with steel plate by arc stud welding method effectively.The connection performance has an important influence on the mechanical properties of steel plate concrete composite structure.During the stud welding process,the instantaneous local uneven heating and cooling process will cause the welding residual stress in the structure,which will adversely affect the structural bearing capacity,stability and fatigue performance.At present,there are relatively few researches on the residual stress of stud welding from domestic and international.It is of great significance to study the influence of residual stress of stud welding on the composite structure.In this paper,the residual stress of stud welding has been obtained by experiment and calculated by FEA method.The influence of residual stress of stud welding on the connection performance of steel plate concrete composite structure is investigated.The details are as follows:(1)The basic principle and process of measuring the residual stress of welding by blind hole method are introduced,and the test plans for measuring the residual stress distribution of welding are designed.Through the calibration test,the strain release coefficients A and B of the test pieces are derived in the uniaxial tension field;the blind hole test is carried out on the stud welded test specimens,which are measured by the strain gauges in three directions.The magnitude and the direction of residual stress are calculated through the strain value.The conclusion that the welding residual stress can't be ignored in the stud welding structures has been obtained,and the welding residual stress at different positions are measured to obtain the regularity of distribution.(2)The ABAQUS finite element simulation analysis of the stud welding heating and cooling process is carried out by the thermal-force indirect coupling method.The distribution of the structural temperature field has been obtained by heat transfer analysis,and the temperature field was used as the temperature load in static general analysis.The calculation shows the variation law and distribution of the stress field during the stud welding process.The results of the analysis obtained by the finite element method are in good agreement with the blind hole tests,which proved accurate and viable of the finite element calculation method.(3)The research on the influence of residual stress of stud welding on the connection performance of steel plate concrete composite structure is carried out.The existence of residual stress field as an initial defect in steel after welding,it will cause the changing of the yield surface of the material under the external load stress space,which affects the mechanical performance of the steel material.At the same time,the existence of welding residual stress field will affect the tensile performance of the stud.and the tensile stiffness of the stud will decreases within a certain range,so that the nonlinearly segment will appear in the original elastic-plastic constitutive relation of the steel and a new constitutive model considering the influence of welding residual stress is proposed.