Project Snapshop
Project: Dumbarton Bridge Seismic Safety Project
Location: San Francisco Bay Area, California
Application: Main bridge crossing lift and leveling
Challenge: Cycle up to 96 high-tonnage jacks during two three-day closures
Solution: Vacuum system that retracted eight 400-ton jacks in under seven minutes
Result: Bridge work completed within the scheduled closures
Shimmick Construction contacted CH Bull while preparing its bid for the Dumbarton Bridge Seismic Safety Project. After reviewing the work with CH Bull high-tonnage jacking specialist Stan Sheppard, the team determined that the project required a specialized system capable of supporting a load of up to 32,000 tons across as many as 96 jacking points.
The system would be used to raise the bridge’s main channel crossing so the contractor could complete seismic upgrades, level the structure, and repave the bridge during two planned three-day closures.
The Challenge
The contractor used low-profile, single-acting locknut jacks with capacities of 300 and 400 tons. Because the bridge had to be raised and leveled incrementally, some jacks needed to be cycled as many as five times.
At each stage, crews raised the bridge approximately one inch, secured the load with the jack’s locking collar, and added steel cribbing plates. Once the cribbing was in place, the load was removed from the jack so it could be reset for the next cycle.
The difficulty was that the load-return jacks would not retract once the weight was removed. Manually resetting numerous jacks would take too long and threaten the project’s limited closure schedule.
The diagram below shows the five-foot lift required to install new seismic bearings at Piers 16 and 31.
The CH Bull Solution
CH Bull designed a vacuum-powered retraction system that could fully retract eight 400-ton locknut jacks in less than seven minutes.
The system allowed crews to reset groups of jacks quickly after each lift, reposition the equipment, and continue raising the bridge. This rapid cycling was especially important at locations where the jacks had to be advanced and retracted up to five times.
Project Outcome
The custom vacuum system retracted eight 400-ton locknut jacks in less than seven minutes, allowing crews to reset and cycle the equipment as many as five times. This preserved valuable time for the seismic, leveling, repaving, and other work required during the scheduled closures.
Need Support for a High-Tonnage Jacking Project?
CH Bull supplies hydraulic jacks, pumps, controls, custom retraction systems, and complete equipment packages for bridge lifting, structural positioning, and other heavy-load applications.