Investigation the Accuracy of Static Analysis Method in Comparison with Spectral Dynamic and Time History Analyses in Steel Structures with Mass Irregularity

There are several methods for structural analysis and design, one of which is equivalent to static analysis. There are limitations. 4 models are examined in this research, the general shape of the plan of a five-story frame, in the first sample is a regular frame, the second sample is a mass irregularity in the first floor, the third sample is a mass irregularity in the third floor and the fourth sample is a mass irregularity in the fifth floor and Its seismic loading has been studied using the standard design spectrum of 2800 fourth edition. Mass irregularities in the first floor with a difference of 45% were higher than other classes and mass irregularities in the third floor were 15% less than the regular sample. Dynamic time history analysis was performed using different near and far fault earthquakes. Responses of lateral and relative displacement were calculated for different stories and compared with the allowable values of the regulations. As a deductive result of this study, we can point to the conservatism of the equivalent static method in estimating the incision and the inability of this method to consider the shape of the load. The results show a decrease in the seismic capacity of structures with mass irregularities in height and therefore it is recommended to avoid creating mass irregularities in height as much as possible.