Study On Behavior Of Stud Welding Steel Reinforced Concrete Columns Under Combined Torsion

Steel reinforced concrete structure has the characteristics of excellent bearing capacity and seismic performance,and is widely used in high-rise,large-span,and heavy-duty structures.Because the surface of the section steel is smooth,in order to improve the adhesion between it and the concrete,a certain number of studs are usually welded on the surface of the section steel.In actual engineering,steel reinforced concrete structures are often under the combined force of compression,bending,shear and torsion.Especially under the action of earthquakes,the existence of torque aggravates the damage of the components.However,there is not much research on the seismic performance of steel reinforced concrete structures under compound torsion.There is also a lack of scientific guidance in the application process of the design of composite structures in my country.Therefore,the development of anti-seismic performance of welded stud steel concrete under compound torsion The research provided by SRC provides a basis for the popularization and application of steel reinforced concrete structures,which is of great significance.This paper considers the steel ratio,longitudinal reinforcement ratio,stirrup ratio,stud spacing and stud arrangement form,and designs 12 stud welded steel concrete members under combined stress of compression,bending,shear and torsion for pseudo-static loading.Observed the development of component failure form,and obtained the load,displacement data of the whole process.The influence laws of various factors on the strength,stiffness,energy consumption,ductility and other seismic performance of components are divided,and reasonable suggestions for structural measures are given.Considering the correlation between compression,bending,shear and torsion,combined with the principle of equivalent superposition,the theoretical calculation formula for the torsional bearing capacity of welded stud-type steel concrete columns under compound torsion is obtained.Finally,the theoretical calculation formula is improved based on the test data,and the empirical calculation formula for the torsion bearing capacity is obtained.The main conclusions are as follows:(1)Under the combined action of compression,bending,shear and torsion,when the stud welded steel concrete seismic performance test component finally fails,the diagonal cracks on each surface will cross and connect,forming a spatial spiral crack,which is a typical torsion failure;the horizontal tension cracks in the middle and lower parts of the component are connected with each other.Vertical compression cracks and shear concrete crushed and fell off in a large area.The longitudinal bars yielded under bending,the stirrups and studs were exposed,and the components were seriously damaged.(2)The load-displacement hysteresis curve and torque-angle hysteresis curve of the component are not greatly affected by factors such as the steel ratio,longitudinal reinforcement ratio,stirrup ratio,stud spacing and stud arrangement form.The former has a full shuttle shape,while the latter has a reverse "S" shape with obvious pinching characteristics.The slope of the rising section of the skeleton curve of components with different factors is similar,but the falling section is quite different.The flexural energy dissipation of welded stud welded steel concrete is dominant,approximately 1.05～1.65 times the energy consumption of torsion resistance,and the presence of torque has an adverse effect on the bending deformation of the component(3)With the increase in the ratio of section steel,longitudinal reinforcement,and stirrup reinforcement,the flexural,torsional and seismic performance of components are improved.Properly reducing the stud spacing can improve the flexural and seismic performance of components,but the improvement effect does not always increase with the reduction of the stud spacing.On the contrary,the excessively dense stud spacing reduces the effect of improvement.The use of fine and dense stirrups that are thicker and less sparse has a better effect on improving the energy dissipation capacity,stiffness degradation,ductility,deformation and other torsional seismic performance of components.Among the stud arrangements,single-double and "X"-shaped studs have the best effect on improving the deformation,ductility,energy consumption and other seismic performance of components.Wing studs have a better anti-torsion effect than web studs.(4)Based on the variable angle space truss model theory,using the equivalent and simplified principle,the unified strength equation of welded stud steel concrete under compound torsion is obtained,and then combined with the superposition theory,the theoretical calculation formula of the component torque bearing capacity is obtained.Combined with the superposition theory,the calculation formula of the component torque bearing capacity is obtained.Finally,considering the synergistic work of steel and concrete enhancement,peg enhancement,combined with the test data to give the pressure bending shear torsion composite action of the welded stud torsional load bearing capacity fitting formula.