In recent years, because of the frequency of earthquakes,steel has been widely used in the construction of civilian residential structures owing to its excellent seismic performance.However,considering that steel structures are widely used,there is a durability problem because of steel corrosion,which has become increasingly serious.Corrosion weakens steel member cross-sections and reduces steel's mechanical properties,ultimately affecting the seismic performance of steel structures.Seismic vulnerability analysis can be used to predict the damage probability at different levels of a structure under earthquakes of different magnitudes.As such,it has an important application value in seismic design,reinforcement,and maintenance decisions regarding structures.Seismic vulnerability research methods include empirical,testing,and analytical methods or a combination of two of these methods.For the most seismic hazard data,empirical vulnerability is the most accurate method,but not all areas experience an adequate number of earthquakes for researchers to obtain sufficient data to evaluate the structural damage probability at all levels.Experimental study methods of vulnerability analysis are also credible,but their costs are relatively high.Compared with the abovementioned two methods,an advantage of the analytical method of determining vulnerability is that it is a rapid and low-cost approach.The main factors that affect the seismic vulnerability of building structures are structural type,architectural age (including specifications and construction period of building design),intensity of fortification,site class,and number of layers.While research on the seismic vulnerability of various structures is quite mature,there has been scant consideration of the impact of service age on the seismic vulnerability of building structures or fragility curves of multiage structures.Based on the time-varying seismic damage model,we propose the use of an analysis method that includes the probabilistic seismic vulnerability steps of multiage steel frame structures under the corrosive action at an acidic atmospheric environment.We consider the influence of service age on the seismic performance of steel frame structures and establish the time-varying probabilistic seismic demand model,time-varying probabilistic seismic capacity model,and time-varying vulnerability model.Based on our analysis of the probabilistic seismic demand and probabilistic seismic capacity,we obtain a vulnerability model and vulnerability curve for multiage (20,30,40,and 50 years) steel frame structures.