Performance of Steel Structures and Associated Lessons to be Learned from November 12, 2017, Sarpol-e Zahab-Ezgeleh Earthquake (MW 7.3)

Sarpol-e Zahab - Ezgeleh earthquake (MW 7.3) occurred in Kermanshah province of Iran near the Iraq and Iran border region on November 12, 2017 at 18:18 UTC (21:48 local time). The epicenter was located about 5 m from Ezgeleh town with a focal depth of about 23 km. Sarpol-e Zahab - Ezgeleh earthquake is the most destructive seismic event in Iran in recent decade in terms of financial and human losses. Based on field observations, carried out by the authors between 25 and 30 November 2017, heavy non-structural and structural damages were occurred to all types of steel lateral load resisting systems, including concentrically and eccentrically braced frames and moment resisting frames. Early buckling of built-up brace members, excessive out-of-plane deformation in gusset plates, formation of plastic hinges at the column ends and lateral-torsional buckling of link beams were dominant failure modes in damaged steel buildings. Post-earthquake observations showed that damages in steel structures were mostly due to poor construction quality including lack of proper welding in connections, extent of irregularities of the structural system, false structural design, local site effects, and finally lack of enough supervision by "Iran Construction Engineering Organization" (IRCEO) and other responsible organizations. In this paper, observed damages to steel structures were examined and explaneed in detail.