ABSTRACT
The Bear Mountain Bridge spans the Hudson River between Fort Montgomery, New York on the west and the mountain known as “Anthony’s Nose” on the east, near Peekskill, New York. The bridge was completed in 1924 and was listed on the National Register of Historic Places on November 23, 1982. During an in-depth inspection of four panels of the main cables in 1991, numerous wires were found broken due to stress corrosion cracking and it was decided to rehabilitate the cables by unwrapping, oiling and rewrapping them. This work began in March 2000 on the southwest backstay. It was observed that the broken wire ends were moving further apart as the wedging and oiling progressed – an indication that the broken wires were slipping. Immediate action was taken to stabilize the backstay with clamping bands. Subsequently, the other three backstays were similarly clamped prior to allowing them to be unwrapped. The southwest backstay continues to be monitored by acoustic monitors that can detect breaking wires. While a few new wire breaks have been detected, the condition appears to be stabilized since the addition of the clamping bands. The New York State Bridge Authority, with Ammann & Whitney as consulting engineers, subsequently performed a detailed study and developed a design to replace the entire suspension system if it becomes necessary. As an interim measure, the most severely damaged section of the main cables, the southwest backstay, is currently being reinforced by the addition of supplemental structural strands that will be connected to the existing cable saddle and tower steel and to a new anchor frame on a new concrete block foundation anchored to bedrock with high-capacity rock anchors. Permanent strain gauges will be installed to monitor the loads in the rock anchors and structural strands. Field work began in March 2006 and will be completed in the fall of 2006.
