Seismic performance of Alaskan structures

Abstract

Alaska is the most earthquake prone area in the United States. On October 23, 2002 a 6.7 magnitude earthquake occurred in interior Alaska. This was followed by a magnitude 7.9 earthquake that occurred near Denali on November 3, 2002. The Denali earthquake was the largest inland earthquake in North America in almost 150 years. Only minimal structural damage was reported. Subsequently, structural engineers should question why minimal damage. As a part of an investigation to evaluate this unusual phenomenon, two structures were selected for seismic analysis, a building and a bridge. The building is at Alyeska Pump Station # 10 (3 miles from the epicenter) and only non-structural damage occurred. A 3 span truss bridge near Tok, Alaska was selected as the second. This structure experienced only minimal damage. Seismic analysis was performed on these two structures for horizontal excitations. A corrected seismic data from Pump Station # 10 was used as the earthquake excitation record. The maximums for displacements, member forces and member stresses were studied. The results show that no structural damage should have occurred for the building and minimal damage for the bridge. These findings compare favorably with field inspection results reported by others.