Study On Tensile Properties Of Self-tapping Screw And A Modeling Approach Of Joints In Nested Light-gauge Steel System

In the nested light-gaugesteel system, there is a big difference between theperformance of the light-gaugesteel and the performance of the steel member connectedwith the hot rolled steel,mainly because of the light-gaugesteel materials used in thenested light-gaugesteel system is more thin than that in ordinary steel structure,Thebasic composition units of light-gaugesteel are produced in the factory, connected byself-tapping screws simply at the processing scene, so that there is no welding processin the whole processing scene. Because of the special construction and installationtechnology, it makes the joints in the nested light-gaugesteel system different from thejoints of ordinary steel structure. In the analysis ofdesign, it can not true reflect thestress and deformation of the joint, no matterthe joint connection is definedashinge,rigid or ordinary semi-rigid.At present, there are a lot studies of semi-rigid joint performance ofcold-formedsteel system, but because most of the research results are based on a largenumber of experimental studies for a specific structure jointto fit out some simplifiedcalculation formulas, and the joints are different from the joints of the nestedlight-gauge steel system, therefore, it has great limitations in the application.In this paper, the author found that the joints’ failure in the structure systemismainly due to the self-drilling screws are uprooted in tension under the action ofbending moment and fittings’deformation failure through the existing experimentphenomenons,self-tapping screw’s shear deformation is not the main factor.Therefore,in order to be able to get asimplified calculation model for this semi-rigidjoint of thisstructure system, this paper conducted a series of experiment researches and analyses.The main work and basic conclusions are as follows:1A series of test researches are carried out for the tensile properties of theself-tapping screws,mainly considering the number of self-tapping screw, whetherfittings are ribbed or not and self-tapping screw rows. Finally, the load-displacementcurve has been got for the self-tappingscrew.2For joint connection innested light-gauge steel system, a simplified calculationmodel of semi-rigid isput forward and compared with the relation curves obtained withZhang Tianping’experiment. Finally, it is discovered that the simplified calculationmodel can revealthe Zhang Tianping’experiment well.3. The joints are improved and using the calculation model of the semi-rigid jointsput forward in this article to calculate the relation curves for the improving jointconnection, at the same time carrying out the corresponding experiment researches.Finally, it proved the feasibility of the calculation model.