Study On Seismic Behavior Of Cold-formed Steel Framing System Of Mid-rise Residential Building Under Horizontal Earthquake Action

Cold-formed steel framing system of mid-rise residential building is a new structural system.In order topromote the application of cold-formed steel framing system of mid-rise residential building in our country,thisthesis firstly studied the seismic resistance of cold-formed steel stud compound wall which played an importantrole in the wind and seismic resistance of this building system,then the seismic behavior of cold-formed steelframing system of mid-rise residential building under horizontal earthquake action was studied by time historyanalysis and performance-based seismic design approach.The study emphases,method and conclusions ofthe investigation were listed as following.1.Full-size tests were carried out to study the seismic resistance of cold-formed steel stud compound wall.The influence of the parameters,including material behavior of sheathing,hole ratios andloading type,on seismic resistance of cold-formed steel stud walls was analyzed by the test.The seismic performances of the composed walls such as failure traits,bearing capacity,ductility were discussed.Comparing with the experimental results in China and abroad,theseresults showed that:â‘ Sheathings influenced wall's shear resistance greatly;and the shearresistance of the double boards cold-formed steel stud compound wall was about equal to the sumof the two kinds of same single board compound wall.â‘¡Aspect ratio had little influence to theshear resistance of walls.With the increase of hole ratios,the specimen's shear-resistance hadclearly decreased.With the increase of stud section,steel thickness and the decrease of studspacing,the wall's load capacity increased obviously.â‘¢With the decrease of screw spacing inthe edge of wall,the wall's load capacity increased obviously.â‘£The shear resistance ofspecimens under monotonic loading increased by 10% that of the specimen under cyclicloading.2.According to the load-story drift curves,the thesis suggested four-linear restoring force modeof cold-formed steel stud compound wall under horizontal load.The characters of stiffness degradation,slip and pinched were showed in the restoring force mode.The thesis also gave the stiffnesscalculative formulas of exponential and hysteresis curves.3.Three-dimensional model of cold-formed steel framing system of mid-rise residential buildingwas established using the ANSYS program to study the mode of the system.Based on the time historyanalysis of the building system under horizontal earthquake action,the thesis suggested thatelastic angular displacement limited value under small earthquake was 1/750 and plasticangular displacement limited value under big earthquake was 1/100 of cold-formed steel framingsystem of mid-rise residential building.According to a detailed parametric study,the thesis draw the conclusion that cold-formed steel framing system was appropriate to be used in six-storeyresidences whose height was 18 meters where the seismic fortification intensity was 8,theheight to width ratio was limited to 3 where the seismic fortification intensity was 7 and 2.5where the seismic fortification intensity was 8.4.A performance-based seismic design approach of cold-formed steel framing system of mid-rise residentialbuilding was put forward through a direct-displacement methodology.According to the current ChineseCode for Seismic Design of Building and the deformation characteristics of this building system,the thesisprovided three different damage limit states corresponding to no damage,repairable and no collapserespectively and the target displacement to these performance levels.Displacement-pattern-basedseismic design method was adopted to analyse the cold-formed steel framing system of mid-riseresidential building.This thesis also suggested the displacement-based seismic design method ofcold-formed steel stud compound wall,and gave the displacement calculative formulas of wall,which could be referred by designers.