Fragility Analysis Of The Low-Rise Cold-Formed Thin-Walled Steel Framing Structure Subject To The Multi-Hazard Actions Of Winds And Earthquakes

Low-rise cold-formed thin-walled steel framing structure buildings have been popularized and applied in some economically developed villages and towns in China due to their light weight,high strength,and conformity to the trend of building industrialization,and they have good development prospects.At present,the multi-hazard problem has become a research hotspot in the field of disaster resistance in construction engineering.Strong wind and earthquake are two common natural disasters that pose a great threat to the safety of building structures.However,for this type of structure,the current disaster-resistant design and disaster loss assessment system is still incomplete;research results on the disaster-resistant performance of non-structural components are also relatively lacking;the effect of some anti-disaster structural measures under the action of multiple-harzard is not clear enough.These problems limit the improvement and further promotion of this kind of buildings.This paper takes a two-story cold-formed thin-walled steel structure as the research object,the fragility analysis of wind-earthquake multi-hazard effects is carried out,and the performance of a structure with anti-multi-harzard structural measures is analyzed and evaluated from the perspective of fragility.The wind-earthquake multi-hazard effects considered in this paper include the separate actions of earthquakes and strong winds and the combination of wind and earthquakes.Firstly,the selection of ground motion records and the simulation of wind load were carried out as the basis of fragility analysis;then,considering the general structure and a structure with an additional structural measure,finite element models were established respectively.Through nonlinear dynamic time history analysis,the response of the structure under various working conditions was analyzed from the top drift and the maximum inter-story drift ratio.Furthermore,taking the general structure as the research object,the wind fragility,the seismic fragility and the fragility of the combination of wind and earthquake were studied.Among them,in terms of wind fragility analysis,a method to comprehensively evaluate the wind resistance performance of the structure from the perspectives of the main structure and the enclosure system was proposed,and the fragility calculation and analysis were carried out.In terms of seismic fragility and the fragility of wind-earthquake combination,based on the method of seismic fragility analysis,through probabilistic seismic demand analysis and probabilistic seismic capability analysis,the fragility curves of the general structure under the conditions of earthquakes and the combination of winds and earthquakes were obtained.Finally,for a structure that adopts anti-multi-hazard structural measures,the fragility analysis under multi-hazard effects was carried out according to the above analysis methods and steps,the results were compared with the general structure and the quantitative evaluation of the role of disaster structural measures was given.The research results show that the main structure of the low-rise cold-formed thin-walled steel structure has good wind resistance,but the enclosure members and the enclosure systems are more susceptible to wind-induced damage.The main structure,the single enclosure member and the enclosure system differ in their fragilities to wind damage due to their different failure mechanisms.It is necessary to conduct separate studies and comprehensively evaluate the overall wind resistance of the structure.The seismic performance of the structure is better under the single action of earthquake.The fragility of the structure under the combination action of wind and earthquake is greater than that under the single action of earthquake.The fragility of the structure increases with the increase of wind speed,but the influence of wind load on the fragility decreases with the increase of ground motion intensity.In general,the dynamic response of the structure with structural measures is lower than that of the original structure,but it is difficult to accurately evaluate its effectiveness only through some time-history analysis results.However,the fragility analysis shows that the addition of structural measures significantly improves the performance of the structure under wind-earthquake multi-hazard actions.