Study On Mechanical Properties Of Concrete Filled Double Skin Steel Tubular(CFDST) Columns Under The Constraint Of Screw-mortise And Tenon Joints

With the rapid development of construction,transportation and water conservancy projects in recent years,some buildings and structures with complex and novel structures and novel appearances have continuously emerged.This has led to gradually increasing requirements for the performance of building materials.Traditional reinforced concrete structures and steel structures Can no longer meet the needs of engineering construction.Therefore,in order to make full use of the characteristics of strong compressive capacity of concrete and strong tensile capacity of steel,scholars have adopted a combination of two structures—steel-concrete composite structure.This structure has better and more efficient performance than steel and concrete structures.Among them,the concrete-filled steel tube structure is a branch of the steel-concrete composite structure,and it is also the most extensively used and widely used composite structure.Along with the emergence of concrete-filled steel tube structures,hollow sandwich concrete-filled steel tube structures have gradually come into people’s sight due to their own low weight,good seismic performance and high bearing capacity.The research of the subject will solve the problems of complex on-site construction technology of hollow sandwich concrete-filled steel tubular members and lack of reasonable joint connection forms.Based on the concepts of “assembled building” and “detachable structure”,a screw-and-tenon joint will be proposed.By connecting the hollow sandwich concrete-filled steel tube columns and steel structural beams with screw-tenon joints,a new type of assembled frame structure stress system of "hollow sandwich concrete-filled steel tube columns-screw-joint joints-steel structural beams" can be formed.The research focuses on the bearing capacity of hollow sandwich concrete-filled steel tube columns constrained by screw joints compared with hollow sandwich concrete-filled steel tube columns constrained by ordinary joints.The subject adopts the methods of theoretical analysis,experimental research,and numerical analysis to verify and compare,and concludes:(1)All the specimens are in-plane elastoplastic instability failure.The loaded specimens show excessive bending deformation at 1/2 places,obvious bulging of the steel tube on the compression side,and no obvious damage at the root of the specimen;(2)The bearing capacity of the test piece constrained by screw joints becomes larger with the increase of the screw length.The load capacity of the test piece composed of the 400 mm screw length and the test piece constrained by ordinary nodes is only 1.2 k N;(3)Due to the existence of the screw,the test piece constrained by the bolt-and-tenon joint makes the lateral displacement of the component at the limit load smaller than the lateral displacement of the component under the constraint of the ordinary node;(4)The screws in the screw joints are in an elastic state through tests and finite element analysis,and can be reused to meet the requirements of green and energy-saving buildings.