عنوان مقاله [English]
In recent years, most of the major seismic design codes have placed emphasis on Performance Based Design of structures. However, these methods are computationally complex and time-consuming, and encouraged researchers to seek new and efficient methods to investigate performance of structures under different intensities of seismic loading. This paper provides better insight into the dynamic behavior of structures in continuous performance levels by Endurance Time (ET) analysis and uses this method to evaluate seismic
performance of Steel Frames. Due to significant reduction in number of time history analyses for assessment of structural response at different intensities, ET method is considered to be a useful tool for conducting practical Performance Based Design of structures. In this procedure, with each analysis of structure under ET acceleration function, the structural response can be estimated in different performance levels. For more precise results, one
can use 3 ET acceleration functions and consider the average of responses as the response of structure. Endurance Time analysis is based on time history analysis, however in this method structure is subjected to gradually intensifying acceleration function and different damage indices of the structure are evaluated through analysis time. The different duration of ET acceleration functions, represents diverse intensities of earthquakes in
different hazard levels. Various inelastic moment resisting steel frames were investiged in different hazard levels. The performance of the structures under seismic excitation in different performance levels is evaluated based on
interstory drift ratios and story shear forces. To ensure accuracy of ET method, the results were compared to the results of nonlinear time history analysis of two sets of ground motions. It was observed that Endurance Time accelerogram led to a very reasonable prediction of structure behavior at various earthquake records. It was also shown that ET predictions are not sensitive to selected ground motions as long as the average spectral intensity remains consistent. Therefore, Endurance Time Method significantly decreases amount of computation in each seismic evaluation analysis. In this research, ASCE-41 is used as the performance base design criterion.