Evaluation of Seismic Performance Parameters of Steel Moment Frames Using Conventional and Advanced Pushover Methods with Considering Higher Mode and Near Field Pulse-Type Effects

Abstract

Ductility, over-strength, material properties and design methodology are the factors affect the reduction rate of the lateral strength of structure in nonlinear region. These factors are introduced as Seismic Performance Parameters, SPP, in technical literature. In seismic codes, the behavior factor, which defines corresponding to the lateral resisting system, covers the aforementioned parameters. Although the R-factor is proposed experimentally, but it could be calculated by means of analytical models in two categories which are demand and capacity R-factor. However, reviewing previous studies reveal that less attention has been paid to the effects of near-fault pulse type earthquakes on R-factor. Therefore, in this study, the SPP is calculated by conventional and advanced pushover methods and the results are compared with the R-factor proposed by Standard 2800-Ver.3. In addition, the effect of load patterns on SPP and capacity curved are considered. The result of this study shows that the proposed R-factor by Standard 2800-3rd for steel special moment frames is conservative for low-rise structures. Increasing the height decreases, the capacity R-factor thus using the R-factor of standard-2800 is inaccurate. The conventional load patterns have no considerable effect on capacity R-factor. In addition, the average of global ductility is about 2 for all models and it is almost independent of the analysis method. At the end, the demand R-factor resulted by near-fault pulse type ground motions is between 0.2 and 0.4 of the value proposed by standard-2800. Therefore, using R-factor introduced by standard-2800 is conservative for the elastic design procedure.

Keywords

• pushover
• behavior factor
• nonlinear demand
• near filed earthquake
• ductility
• seismic performance parameters