Theoretical Analysis And Experimental Study Of T-shaped Columns Comprising Square Concrete-filled Steel Tubes Bearing Capacity Under Axis Compression

Steel-concrete composite structure can complement the material performance of steel and concrete.It has been widely used in civil engineering structures,especially in high-rise buildings.When steel-structure residential buildings adopt concrete-filled steel tubular special-section columns,it not only saves space,but also facilitates the placement of furniture items,and meets the aesthetic requirements.At present,the types of special-shaped columns mainly include reinforced concrete special-shaped columns,steel reinforced concrete special-shaped columns and concrete filled steel tubular special-shaped columns.On the basis of summarizing and analyzing the above types of special-shaped columns,this paper puts forward a new type of special-shaped column-T-shaped concrete filled square tubular composite special-shaped columns,that is,L-shaped,T-shaped,cross-shaped and other special-shaped sections formed by welding multiple square concrete filled steel tubular columns.Noodles.Through experimental study,theoretical analysis and numerical simulation,the mechanical properties and working mechanism of T-shaped concrete filled square steel tubular composite special-shaped columns under axial compression are studied in depth.Five T-shaped concrete filled square steel tubular composite special-shaped columns were tested under static axial pressure,and the effects of steel content,steel strength,slenderness ratio and other factors on the failure mode,ultimate bearing capacity,ductility and other mechanical properties of the specimens were analyzed.A finite element analysis model consistent with the test was established,and the effects of steel strength,steel tube thickness and concrete strength on the poles of the members were analyzed and quantified.Increasing the limited bearing capacity;Comparing and analyzing the formulas for calculating the strength and bearing capacity of composite columns in national codes,and according to the results of experiment and numericalsimulation,the formulas for calculating the strength and bearing capacity of T-shaped concrete filled square steel tubular composite special-shaped columns are obtained;In view of the two commonly used methods for calculating the stability coefficient of composite columns,the results of calculation are compared with those of experiment and numerical simulation.Based on the analysis and the actual needs of the project,the formula of the stability bearing capacity of T-shaped concrete filled square steel tubular composite special-shaped columns is obtained.The main achievements are as follows:(1)In T-shaped concrete filled square steel tubular composite special-shaped columns,the short column members eventually show the characteristics of central buckling failure and local buckling failure at the end,showing typical strength failure;the long column members mainly show the characteristics of overall buckling failure,showing typical stability failure;the weld seam between the steel tube and the steel tube of the specimen does not crack,and the steel tube is not cracked.The cooperative working performance with concrete,steel tube and steel tube is better,and the specimen presents better integrity.(2)The load-deformation curves,failure modes and ultimate bearing capacity of the components simulated by finite element software are consistent with the test results,which shows that the finite element model established in this paper can better simulate the test.The model can be used to supplement the axial compression test of T-shaped concrete filled square steel tubular composite special-shaped columns;in the finite element parametric analysis,along with steel-contained concrete composite special-shaped columns.Increasing the ratio,steel strength and concrete strength can increase the bearing capacity of T-shaped concrete-filled square steel tubular composite special-shaped columns by 23.7%,22.7% and 12%,respectively.That is to say,the influence of steel tube thickness and steel strength on the bearing capacity of members is nearly the same,and the influence of concrete strength on the bearing capacity of members is the weakest.Therefore,in practical engineering,if it is necessary to improve the bearing capacity of members,the first choice is to increase the steel content and steel.Strength.(3)The results calculated by AIJ code are the closest to the experimental and simulation results.The simplified calculation method of the axial compression bearing capacity of T-shaped concrete-filled square steel tubular special-shaped columns considering the influence of restraint coefficient and slenderness ratio is proposed.It can predict the axial compression strength andstability bearing capacity of T-shaped concrete-filled square steel tubular special-shaped columns better.It can be used for the design of T-shaped concrete-filled square steel tubular special-shaped columns.It also provides reference for the application in practical engineering.