A new method for the seismic design of plane steel moment resisting frames is developed. This method determines the design base shear of a plane steel frame through modal synthesis and spectrum analysis utilizing different values of the strength reduction (behavior) factor for the modes considered instead of a single common value of that factor for all these modes as it is the case with current seismic codes. The values of these modal strength reduction factors are derived with the aid of a) design equations that provide equivalent linear modal damping ratios for steel moment resisting frames as functions of period, allowable interstorey drift and damage levels and b) the damping reduction factor that modifies elastic acceleration spectra for high levels of damping. Thus, a new performance-based design method is established. The direct dependence of the modal strength reduction factor on desired interstorey drift and damage levels permits the control of deformations without their determination and secures that deformations will not exceed these levels. By means of certain seismic design examples presented herein, it is demonstrated that the use of different values for the strength reduction factor per mode instead of a single common value for all modes, leads to more accurate results in a more rational way than the codebased ones.
Abdelhakim Bouhadra, Abderahmane Menasria — 1) Civil Engineering Department, University of Khenchela, Faculty of Sciences and Technology, Algeria; 2) Materials and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Algeria
Djamel Eddine Lafi, Abdelkader Tamrabet — Civil Engineering Department, University of Ferhat Abbas, Setif1, Faculty of Technology, Algeria
Salah Refrafi — Civil Engineering Department, University of Khenchela, Faculty of Sciences and Technology, Algeria
Hayat Benachi — 1) Civil Engineering Department, University of Khenchela, Faculty of Sciences and Technology, Algeria; 2) Laboratory of Engineering and Sciences of Advanced Materials, BP 1252 Road of Batna, Khenchela 40000, Algeria
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