Evaluation of a Steel Girder Bridge Collapse during Deck Removal

Abstract

The evaluation of a welded, steel girder bridge that once crossed the Rio Puerco River near Albuquerque, New Mexico, is presented in this study. Following 44 years of service, the bridge was scheduled for total replacement due to the poor condition of the structure. On May 18, 2011, the bridge girders collapsed due to lateral torsional buckling during removal of the concrete deck, resulting in a few injuries but luckily no loss of life. The buckling resistance of the compression flange of the steel girders was evaluated. Dead load and live load effects were determined from three-dimensional analyses. The results presented herein show that the deck removal procedure was not structurally sound and the compression-flange flexural capacity was exceeded in the exterior girder due to inadequate bracing, which initiated the bridge collapse. Following buckling of the exterior girder, load redistribution to the remaining girders resulted in demand versus capacity ratios exceeding 1, and ultimately progressive collapse of the entire bridge.