Type: Vertical Lift Bridge
Location: Tacoma, WA
Client: Washington State Department of Transportation
Stafford Bandlow Engineering personnel conducted an in-depth inspection of the operating ropes and main counterweight ropes on this historic vertical lift bridge. At the time of inspection all main counterweight ropes were original and dated to 1912.
Field work included visual and hands-on inspection of the full length of all ropes using Spyder baskets to traverse from the lift span to the tower level. Wear flats on the crowns of the wires were evaluated and documented. Measurements were taken to document rope diameter and rope lay length at 3 pre-defined locations along the length of each rope. The ropes were cleaned to bare metal at a select number of locations to assess the lubricant as well the condition of the underlying wires. Rope tension measurements were performed on all ropes. The integrity of the rope sockets and rope termination plates at the span and counterweight ends was also assessed. Based on a combined assessment of the observed and measured conditions, 2 ropes were selected to be removed from the structure and subjected to a break test to establish the ultimate strength of the ropes. A full report was prepared to document the inspection findings with photo documentation of all significant conditions and recommendations for corrective action and cost estimates.