عنوان مقاله [English]
Appropriate seismic design is based on real understanding of structural behavior. This requires precise perception of structural behavior during earthquakes which will beachieved by considering various codes' criteria. In other words, an ideal seismic design is
a method which directly considers non-linear behavior and designs frames in a way that they experience their maximum capacity, it means plastic hinges occur in frames. The plastic hinge locations should be far from joints between beams and columns. In this way, local instability does not occur. Actually, more accurate recognition of structural behavior during earthquakes is the main issue of this research. For this purpose, regular steel- moment frames with medium ductility and height were designed based on resistance (force), direct displacement, energy and plastic hinge methods. All the models were developed in OpenSees computer program, and they were analyzed through non-linear time history. Three records, according to record magnitude, fault distance, and soil type, were used from Pacific Earthquake Engineering Research Center (PEER) (Kobe, Northridge, and Tabas). Ultimately, these records were coordinated based on Iranian Standard No. 2800. Then, frames were evaluated with various codes' criteria in order to represent a new formula for maximum roof allowed displacement (for the purpose of controlling structural behavior after design).This formula is based on maximum displacement that frames have experienced during different earthquake records in non-linear time history analysis. The result indicates that the new formula allows more displacement to structures in comparison to Iranian Standard No. 2800. According to displacement time history of designed frames, at the beginning of the earthquake, the structures experienced severe impact and their nonlinear behavior was started. The transient displacement occurred when the first impact was applied to structure, and it was a displacement which happened along with the first plastic hinge occurrence. It makes sudden shock in displacement time history curve. With the passage of time, structures experienced variable displacements, and finally, a permanent displacement remained which is for the sake of nonlinear analyzing. Also, it can be inferred from the results that direct displacement and force methods present maximum and minimum base shears, respectively. In addition, in all frames, plastic hinge method provides maximum period value in comparison to other methods. It reveals that those frames which have been designed with plastic hinge method are more flexible. According to the results, the difference between direct displacement and energy methods period values is low, and period value of energy method is the minimum, as well.