Study On Seismic Behavior Of Semi-rigid Joint With Double Cold-formed Thin-walled C Steel

Cold-formed thin-walled steel is recommended continuously in the buildingengineering with its high utilization and better seismic behavior. But the application ofcold-formed steel is still limited to several kinds of section forms specified in the"Technical specification for low-rise cold-formed thin-walled steel buildings". In order toexpand the application of cold-formed thin-walled steel structure in the residentialbuildings, a new kind of compound section is suggested to study the seismic behavior ofthe joints of which has double cold-formed C steel, connected with gusset plate and bolts.Firstly, ANSYS was used to model the inclined joint with double cold-formed C steel. Bycomparing with the previous test results, the model was reliable. Twenty joints were computedunder cyclic loading by using this modeling method, and various influencing factors wereconsidered. The stress nephogram, M-θ hysteresis curve and skeleton curve were all got fromthe computing results. By analyzing the failure modes, ultimate bearing capacity, initial rigidity,rigidity degradation, ductility and energy dissipation of the joints, the influence of every factorwas discussed to evaluate the seismic behavior of the joints, and some design suggestions weregiven. The results show that this kind of joints have two main failure modes, i.e flexuralbuckling of beam and flexural-torsional buckling of gusset plate, and bolts slipping individuallyappear during the destruction.The gusset plate thickness, bolt pitch, C steel thickness, webheight and roof pitch have different influences on the bearing capacity and initial rigidity. Therigiditydegradation, ductility and energydissipationofthe joint withbeam flexural buckling arebetter than the joint with flexural-torsional buckling of gusset plate, and it has equal values toother kind of joints. But if it is compared with the same kind of rectangular joint, it has slightlypoorer ductility. In order to meet the requirements of anti-seismic design, the suggestion thatbolt diameter and gusset plate thickness should respectively be no less than12mm and6mm,with bolt pitch ranging from200mm to220mmare presented. When the height ofC steel webis more than180mm, the gusset platethickness should be between8and10mmappropriately.Secondly, to study the influences of main factors on the semi-rigid characters, sixteenjoints were designed and analyzed by using orthogonal test design method withmulti-factor. The ultimate bearing capacity and initial rigidity were selected as the objects to test the significance of the factors. The optimal level combinations of the factors werealso given. Finally, through mathematical statistic method, the mathematical modelsbetween the factors and ultimate bearing capacity, initial rigidity and rigidity degradationwere established, respectively. With regression fitting, some empirical formulas were gotwhich could be as references in structure design, and also could be described the semi-rigidcharacters of the joint quantitatively.The research results could lay solid foundation of engineering application for the newkindofcold-formed steel joint, and provide references for engineering design.