Floor System Evaluation of a Riveted Steel Arch Bridge

Abstract

The Omega Bridge is a riveted, steel arch bridge built in the early 1950s to cross the Los Alamos Canyon and connect the town of Los Alamos, New Mexico to technical areas of the Los Alamos National Laboratory. The alternate route from the bridge runs through the canyon on a steep grade, which is not a suitable option, particularly for emergency vehicles such as fire trucks. In the early 1990s, the bridge was rehabilitated due to the poor condition of the deck and increased traffic demands, which resulted in several changes to the original structure. This paper discusses the load rating of the bridge as affected by the rehabilitation according to the AASHTO load factor rating method. Attention is given to the evaluation of the floor system components including the stringers, floor beams, and spandrel beams. It is shown that the Omega Bridge is in satisfactory structural condition, no load posting is necessary, and the bridge is safe for the passing of emergency response vehicles.