Behrouz Shafei - MSc Student of Civil-Structural Engineering, School of Civil Engineering, University of Tehran
Pierino Lestuzzi - Lecturer, Swiss Federal Institute of Technology Lausanne, Switzerland
Masoud Motavalli - Head of Structural Engineering Research Laboratory, EMPA, Switzerland Assistant Professor, School of Civil Engineering, University of Tehran
Rasoul Rasoul - Assistant Professor, School of Civil Engineering, University of Tehran

When damaged Moment Resisting Frames were first discovered following the 1994 Northridge earthquake, there was speculation that this was a result of some peculiar characteristic of the earthquake itself or of local design and construction practices in the Los Angeles region. It has now been confirmed that similar damage occurred to some buildings affected by the 1989 Loma Prieta earthquake and also the 1992 Landers and Big Bear earthquakes. In 1995, the Kobe earthquake resulted in damage to several hundred steel buildings, and the collapse of 50 older steel buildings. Japanese researchers have confirmed problems similar to those experienced in the Northridge earthquake. Engineering researchers around the world have recognized this behavior as a common problem for welded steel moment-frame buildings designed and constructed using practices prevalent prior to the Northridge earthquake. Studies conducted to reduce earthquake hazards in welded moment-resisting steel frames confirm that some of the design requirements contained in the building codes prior to the Northridge earthquake were inadequate. This paper describes seismic provisions given in AISC (American Institute of Steel Construction) hereafter referred to as AISC-Seismic Provisions as a series of additional criteria for the design and construction of steel moment-frame buildings. These seismic regulations make performance of these structures in future earthquakes much more reliable. It is recommended that the building codes adopt these new recommendations and that, until this occurs, designers voluntarily adopt these criteria when developing new buildings.

Moment Resisting Frame (MRF), Seismic Provisions, Steel Buildings, Earthquake- Resisting System, Ductile Design