| Cold-formed steel(CFS)structure,which originates from the wood structure,is a new type of structure system composed of CFS framed shear walls,composite slabs,composite roofs and foundation.The CFS building has the advantage of good seismic performance,green environmental protection and construction speed,which adapts to the development of housing industry,building standardization and assemblage of civil architecture.As the CFS structure develops,multi-story CFS building has gained popularity in the 21 century.However,it is not mature and there are so many problems in theoretical research and engineering practice of the multi-story CFS structure compared with conventional CFS framed walls.In order to promote the multi-story CFS building,this paper puts forward the CFS shear wall sheathed with steel sheets for the base layer combined with gypsum wallboards for the face layer on the basis of conventional CFS framed walls.The author presented experimental and numerical investigation of seismic behavior on these CFS shear walls,and established the simplified dynamic analysis model of multi-story CFS buildings to investigate its seismic behavior.In this paper,the content and conclusions are stated as follows:1.The author conducted nine full-scale wall tests with different assemblies,which were tested under either monotonic load or cyclic load without the vertical load.The wall configurations differed in terms of framing and sheathing thickness,sheathing material,wall aspect ratio and loading mode.The failure mechanism,bearing capacity,displacement,lateral stiffness,shear strength,and ductility of specimens were obtained.The following conclusions can be drawn.①There occurred two types of predominant failure modes,which were dominated by chord-stud failure and sheathing connection failure respectively.②The failure modes were controlled by the ratio of framing to sheathing thickness,which increased with more obvious ductile failure mode.③The increase of wall aspect ratio led to lower lateral stiffness and ductility,but had no effect on shear resistance.④The increase of framing and sheathing thickness resulted in higher shear resistance,lateral stiffness and ductility.⑤Using gypsum wallboards for the face layer on both sides could achieve higher shear resistance but lower ductility.⑥The shear resistance of walls dominated by chord-stud failure depended on their chord-studs.2.The finite element software ABAQUS was used to simulate the monotonic behavior of CFS shear walls,when screw connections,hold-downs,material and geometric nonlinearity were considered.Comparing numerical and experimental results,in terms of yield load and displacement,peak load and displacement,shear strength and failure modes,showed that the numerical model is very capable of estimating the seismic behavior of actual CFS shear wall.The structural analysis software OpenSEES was used in developing nonlinear simplified models of reversed cyclic shear wall tests.The yield load and displacement,peak load and displacement,damage load and displacement of nonlinear simplified analysis were close to those of tests,when the hysteresis loops obtained from OpenSEES presented significant pinch effect and degradation of strength and stiffness.3.The OpenSEES was utilized to create nonlinear simplified 3D dynamic analysis models of multi-story CFS buildings.In order to evaluate the seismic behavior of the simplified dynamic analysis models,the response spectrum analysis was carried out for the structure corresponding to the 7th,8th and 9th degree frequent earthquake,while the time history analysis was carried out for the structure corresponding to the 7th,8th and 9th degree rare earthquake.The results of simplified dynamic analysis are as follows.①The natural vibration periods of simplified dynamic models were close to those calculated from cold-formed steel specification in China,America and Japan.②Using more new-type CFS framed shear walls with steel sheathing in the multi-story CFS buildings led to smaller natural period but higher stiffness.③Compared with conventional CFS buildings,the maximum story drift angles of New-type CFS structures were reduced by up to 34.7%,35.8%and 51.3%for 7th,8th and 9th degree frequent earthquake and 48.7%,36.9%and 39.2%for 7th,8th and 9th degree rare earthquake.④The new-type CFS framed shear walls with steel sheathing is well suited for multi-story buildings in highly seismic regions.In order to promote the multi-story CFS building,this paper presented experimental and numerical investigation of seismic behavior on these CFS shear wall,and established the simplified dynamic analysis model of multi-story CFS structures.This study provides a theoretical support for the engineering practice and aseismic design of multi-story CFS structures. |
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