Effects of Capacity Design Rules on Seismic Performance of Steel Moment Resisting Frames M. T. Naqash & G. De Matteis University “G. d’Annunzio” of Chieti-Pescara, Italy A. De Luca University of Naples “Federico II”, Naples, Italy SUMMARY: The current paper deals with the seismic design of 9-Storey office building using Eurocode 8 and AISC (American Institute of Steel Construction) provisions, where the seismic load resisting system is composed of either spatial or perimeter moment resisting frames. According to EC8, Ductility Class High (DCH) and Ductility Class Medium (DCM) with behaviour factor of 6.5 and 4.0 respectively, are used. Whereas in the case of AISC code, only Special Moment resisting Frame (SMF) with response modification factor of 8 is employed. In order to shed light on the pros and cons of the design criteria and thus the influence on the capacity design rules of the two aforementioned codes, designed frames are analysed by non-linear static analysis. The frame performances are measured in terms of overstrength and redundancy factors, strength demand to capacity and drift demand to capacity ratios, allowing interesting conclusions to be drawn. Keywords: Seismic codes, Moment resisting steel frames, Seismic resistance, Pushover analysis 1. INTRODUCTION To control global structural behaviour, codes give the so called criterion of capacity design where non- dissipative members are designed for comparatively higher seismic forces than dissipative members and where dissipative members are kept at such locations that will fail before the brittle members and subsequently will protect non-ductile elements by overstressing. Capacity design has been initially recommended in the seismic code of New Zealand. In particular, (Paulay and Priestley, 1992) and (Priestley, 2003) proposed weak beam and strong column concept in the design of moment resisting frames by suggesting of providing reduce stiffness of beams than columns. (Nassar and Krawinkler, 1991) and (Miranda and Bertero, 1994) examined the force reduction factors, providing a detailed discussions and improvements on the ductility reduction factors. Further, (Bertero, 1991) discussed the influence of overstrength factor on the performance of structures designed according to the codified formulations. Also (Sanchez‐Ricart and Plumier, 2008) investigated overstrength factors for frames, highlighting the concept of capacity design. (Rahgozar and Humar, 1998) assessed the extent of reserve strength attributable to redistribution in steel frames. (Ballio et al., 1988) provided extensive studies to justify definition values of the reduction factor in ECCS Manual 1988 (Design of steel structures in seismic zones). Further, (Hasegawa et al., 2000) assessed the perimeter frame designed according to U.S. procedure and spatial frame according to Japanese codes to evaluate the major differences between the two configurations. (Elghazouli, 2010) extensively contributed in the assessment of European seismic design procedures and philosophies for several lateral load resisting systems, especially concerning moment resisting frames due to their paramount inelastic behaviour. The presented paper is aimed at providing useful information for readers and technicians who are involved in the design of MRFs according to the European and American codes. 2. CAPACITY DESIGN OF MRFS: EUROPEAN VS. AMERICAN SEISMIC CODES In order to provide a comparison of the capacity design rules in Eurocodes ((EN-1993-1-1, 2005)-