Axial Compression Design Method Of Cold-formed Steel Columns With Holes In Web And Its Effect On Shear And Insulation Performance Of Composite Walls

The cold-formed steel(CFS)structure are light weight and high strength,environmental protection and energy saving,and convenient construction.It meets the needs of China's vigorous development of prefabricated buildings and green buildings,and has a wide application prospect.Due to the late start of China's research on CFS structure,compared with developed countries such as Europe and the United States,China's standards about CFS structure need to be improved.Thus,this paper researched on the influence of the hole parameters on the columns with holes,the design method of the CFS columns with holes,shear and thermal insulation performance of cold-formed steel composite wall assembled by columns with holes.The main contents and conclusions are as follows:1.A finite element model for column buckling analysis and nonlinear buckling analysis was established by using the finite element numerical simulation software ABAQUS,and verified by experimental and simulation data in the literature.Then,the effects of hole width,hole length,number of holes,and hole location on the critical elastic buckling load and ultimate load of C-shape CFS columns with holes under simple and fixed support conditions were analyzed.The following conclusions are obtained:(1)The influence of holes on the critical elastic buckling load and ultimate load of columns under simple support and fixed support conditions are similar.(2)When the hole width is small,the critical elastic local buckling load of the column decreases slightly as the hole width increases;when the hole width is large,the critical elastic local buckling load of the column becomes larger as the hole width increases.For short columns(distortion buckling half-wave length is less than twice the column length),as the hole width increases,the critical elastic distortion buckling load of the columns becomes larger;for long columns(distortion buckling half-wave length is more than twice the column length),the hole width impact on column critical elastic distortion buckling load is small.The hole width has no significant effect on the critical elastic global buckling load.The critical elastic local buckling load increases as the hole length increases;the critical elastic distortion buckling load of the long columns decreases as the hole length increases;the critical elastic distortion buckling load of the short columns increases first and then decreases with the increase of the hole length;The number of holes and the location of holes have no significant effect on the critical elastic local buckling load,critical elastic distortion buckling load,and critical elastic global buckling load.(3)As the hole widthincreasing,the column ultimate load significantly reduced,the reduced amplitude is up to 33%,and the force distribution on columns will change significantly;As the hole length increasing,the ultimate load of the column will also reduce,but the reduced amplitude is not more than 10%;The number and location of holes have no significant effect on the column ultimate load.2.the hole width influence on the column strength failing in global,local and distortion buckling were researched by the finite element software ABAQUS,and the direct strength method for design of C-shape CFS column with holes was proposed.The following conclusions are obtained:(1)H-DSM avoids to determine the perforated column elastic buckling load for calculating column strength.The key to this method is to calculate the hole impact factor and the bearing capacity of column without holes,which are easy to accomplish.(2)H-DSM not only has high accuracy and applicability for design of C-shape CFS column with holes,but also applies to both pined-pined and fixed-fixed boundary conditions,which provides designers with flexible choices.(3)The ideology of H-DSM has critical value for the research on other CFS members with holes(such as joists).3.the shear analysis model of the composite wall was established by the finite element numerical simulation software ABAQUS,and verified by experimental data in the literature.Then,the new composite wall W89-1 developed by our research group was chosen to study on the shear performance of cold-formed steel composite wall assembled by columns with holes.The following conclusions are obtained:(1)the shear performance of the composite wall basically does not change as the hole width,number of hole and hole length changed on stud columns(2)Whether the strengthen side columns or the reinforced side column are used on the composite wall,the holes on column web have no significant effect on the composite wall shear performance.4.the 3D heat transfer analysis model of the composite wall was established by the finite element numerical simulation software ABAQUS,and verified by experimental data in the literature.Then the thermal performance for the new composite exterior wall W140-11 developed by our research group was analyzed,and the hole arrangement method suitable for the composite wall was given.The following conclusions are obtained:(1)The method of arranging sandwich wall panels on the indoor side of the new combined wall W140-11 will effectively prevent indoor heat loss and improve the wall thermal insulation performance.(2)Accordingto JGJ26-2018 "Energy-Saving Design Standards for Residential Buildings in Frigid and Cold Areas",the new combined exterior wall W140-11 developed by our research group can meet the insulation requirements for building that the number of building layers is more than three layers and the building shape factor is not greater than 0.3 or the number of building layers is not more than three layers and the building shape factor is less than 0.55 in the cold area.when the keel column webs of the wall W140-11 are perforated according to the four kinds of hole layout methods given in this paper,it can meet the building insulation requirements for all layers and shape factors.