Experimental Study On Light Steel Frame Wall With New Type Perforated Stud Subjected To Axial Compression

In recent years,cold-formed thin-walled steel has been widely used in the construction industry because of its advantages such as light weight,high industrialization,environmental protection and high recycling rate.The cold-formed thin-walled steel stud wall is the main vertical load-bearing unit in the light steel structure system,which is mainly composed of the cold-formed thin-walled steel frame with sheathing on both sides;several holes are usually set at the wall stud web to facilitate the pipeline crossing;the capacity,buckling mode and stress distribution of the stud will be affected because of web holes.The capacity of a single axial compression stud is significantly affected by the stiffener,while the existing wall stud is still dominated by channels;in addition,the design method of the ultimate load for walls made with web-stiffened studs(with or without web holes)is relatively scarce.Therefore,it is necessary to study the axial compression performance of the web-stiffened wall stud.The axial compression test of four cold-formed thin-walled steel stud walls were carried out,and the influence of cross-section,web holes and sheathing material on the axial compression performance for walls was studied.Compared with the same type of wall without holes,the ultimate load of the un-stiffened and web-stiffened wall studs decreased by about 1.6% and 12.0%,respectively;the instability mode of the un-stiffened wall stud was local buckling,and the setting of web stiffeners made the distortional buckling became its main instability mode.The buckling deformation was more obvious than that of the web stiffened wall stud,so it can be seen that the stiffener effectively limited the deformation of the plate around web hole;the web stiffeners can significantly improve the wall stiffness,but under the same conditions,the holes and the sheathing material had little influence on the wall stiffness,which showed that the vertical stiffness of the wall stud mainly depended on the section characteristics of the stud.The web holes and sheathing didn't play a leading role on the influence for the stiffness.In addition,the nonlinear spring element combine39 was used to simulate the screws connected the steel and the gypsum board,and node coupling method was used to simulate the screws connected the steel and steel,the steel and OSB.The results of the finite element analysis were compared with the test results,which were in good agreement and verified the accuracy of the model.On this basis,the variable parameter analysis of the wall studs with or without web stiffener were carried out.By changing the height,width,spacing of web holes and steel thickness,the influence of each parameter on the axial bearing capacity and instability mode of walls were studied.The results showed that when the height of the hole reaches 1/2 of the height of web,the decrease of the bearing capacity was less than 5%;the parameters distributed along the length of the wall stud,such as the width and spacing of web holes,hadminimal influence on the ultimate bearing capacity of the wall stud;it was indicated that the axial capacity of the wall studs increase with the decrease of flange width-thickness ratio.However,the most striking result to emerge from the data was that distortional buckling strength was improved significantly when the steel thickness was 1.2mm.The equivalent thickness model was established to consider the influence of web holes on the buckling stress of the stud by considering the restraint effect of the panel for the stud,.The direct strength method of a single axial compression member with holes was extended to the walls made with unstiffened studs.Two direct strength calculation methods,,which considered the interaction of local and distortional buckling,were used to calculate the nominal axial strength of the web-stiffened stud walls with holes.Compared with the test and finite element analysis results,however,it was also found that the design method proposed in AS/NZS 4600 provided safe and accurate failure load estimates for web-stiffened wall studs.The conclusion can provide reference for practical engineering application.