Rehabilitation Design of a Bascule Bridge – Including Jacking Up an 800-Ton Bascule Leaf

The 904-foot Hylebos Waterway Bridge was constructed in 1939 and spans the Hylebos Waterway in Tacoma, Washington (USA). It consists of east and west approaches and a 290-foot double-leaf trunnion bascule span crossing the waterway.

This bridge was inoperable after a drive shaft on the east bascule leaf failed in early 2001. In 2004, a fire damaged the main trunnion girder and bearings inside the east bascule pier.

This project includes replacing both approach structures and restoring the bascule main span to operational condition. Project components include:

• Replacing the fire-damaged trunnion bearing

• Modifying the pinion support system to meet current design code

• Seismically retrofitting the bascule leaf structures

• Overhauling the bascule mechanical driving and electrical control systems; and

• Replacing both approaches.

Environmental regulations restrained construction activities, and because the bascule leaf weighed approximately 800 tons, replacing the bearings was a chaUenge. A tight inwater construction window and weak structure layer in the bascule pier's lower portion further complicated the repair effort. The design team developed unique solutions to these challenges and gained valuable experience in rehabilitating movable bridges.

• Abstract

• Project Description

• Existing Bridge and its Deficiencies

• Unique Challenges

• Design Solutions

• Future Consideration