Seismic Behaviors Study On Low-rise Cold-formed Thin-wall Steel Residential Buildings

As a new structural system, low-rise cold-formed thin-wall steel residential buildings have been used in Chinese gradually. However, the research on seismic behaviors of this structural system is seldom involved. To study the seismic behaviors of low-rise cold-formed thin-wall steel residential buildings under horizontal earthquake action, three tests including full scale model test on 10 pieces of wall panels under cyclic horizontal load, self-drilling screw connection test on three groups of specimens and shaking table test on a full scale three-story residential building model have been carried out in this paper. The following test results were obtained respectively: The shearing performance indexes of wall panels such as yield load, maximum load, failure load, energy dissipation coefficient and ductility factor; The shear resistance of self-drilling connection specimens; Dynamic properties, seismic responses, damage features and seismic behaviors etc. of three-story cold-formed thin-wall steel residential building.Based on experimental study, the following theory analysis were developed: The nonlinear finite analysis model was established and a detailed parameter analysis was carried out by ANSYS program; Restoring force model and nonlinear simplified analysis method of cold-formed steel wall panels were studied by using the hysteresis rules of multi-linear plastic Pivot element in SAP2000 program; The simplified dynamic analysis model of cold-formed thin-wall residential building was established, linear and nonlinear seismic response analysis was carried by SAP2000 program. Based on the test results and finite element analysis on cold-formed wall panels, the following conclusions could be suggested: The diagonal bracings are helpful to improve the shear resistance of single-column wall panels while nearly useless to double-column wall panels; The calculation method of the shear resistance of wall panels with openings suggested by Technical Specification for Low-Rise Cold-formed Thin-Wall Steel Buildings is conservative; The shear resistance of double-column wall panels are obviously higher than that of single-column ones; The strain response is largest for columns, less for the transverse bracings and least for the diagonal bracings; As the interface slip between the upper and lower wallboards is obvious, the seams between wallboards should be as little as possible and the transverse continuous seams should be avoided in practice; The initial stiffness of wall panels obtained from test results agree well with those from finite element analysis; As far as wall panels with plasterboards on both sides are concerned, the yield loads of double-column wall panels are higher than those of single-column ones; The initial stiffness, yield load and maximum load of wall panels with plasterboards on both sides are obviously lower than those with OSB board plus plasterboard on both sides.Restoring force model and nonlinear simplified analysis results indicate that the skeleton curves of wall panels can be modeled by the degenerated four-linearity model; the Pivot model parametersαandβcan be taken as 10 and 0.1 for double-column wall panels, while 10 and 0.15 for single-column ones, respectively; the envelope of hysteresis curves and capacity of dissipating energy of wall panels obtained from nonlinear simplified analysis are similar to those from test; the strength degeneration, stiffness degeneration and rheostriction phenomena of wall panels can be well modeled by simplified analysis method.Shaking table test and the simplified dynamic analysis results indicate that the residential building structure is mainly suffered local damage during test, while the cold-formed steel frame is almost undamaged; When seismic fortification intensity is degree 9, the maximum elastic story drift angle of structure under frequent earthquake and that of elastic-plasticity under rare earthquake are 1/934 and 1/52 respectively, which met the demand of Chinese Code for Seismic Design of Buildings; The skin action of wall panels and action to resist overturning moment of hold downs are very important to the lateral resisting of the building structure; Preliminary evaluation shows that the structure safety is guaranteed; The first two modal of residential building obtained from analysis is identical to those from test, and the discrepancy of the fundamental and secondary frequency are 11% and 2% respectively; The simplified dynamic analysis method can be applied to elastic and elasto-plastic seismic response analysis of cold-formed thin-wall residential building.