Showing fancy foot work

October 10, 2000

Keeping the Golden Gate Bridge on solid footing is a significant undertaking. Preparing it to withstand the threats of potential earthquakes makes it all the more important. And accomplishing this task without disrupting day-to-day San Francisco commuter traffic takes it into the realm of the remarkable.

Avoiding delays has been the daily challenge faced and met by the contracting firm of Balfour Beatty Construction Inc., Atlanta, Ga. It has involved construction of temporary support towers and a series of intricate synchronized lifts transferring the loads from the existing bridge onto the temporary supports. The next step is demolition of the old tower and concrete footings, followed by new concrete footings on 2-ft-diam. CIDH shafts and the erection of the new structural steel tower.

In terms of distance, the lifts are short. Massive bridge sections are raised and lowered just two-tenths of an inch at a time. But given the importance and the intricacy of the operation, it is a task that is planned and carried out to the minutest detail. A complex electrohydraulic synchronous lift system was custom built for the application by engineers from Balfour Beatty and Enerpac, a leading international manufacturer of hydraulic equipment and systems based in Milwaukee, Wis.

The lifts and tower restoration are being accomplished as part of a three-stage upgrade of the main bridge and its northern and southern approaches. Estimated total costs for the project, to be completed in October 2005, exceed $297 million.

The project has been carefully monitored and managed under self-imposed design rules that are stricter than those required at the start of the project. It has progressed steadily toward its scheduled completion, successfully fulfilling its dual mission of solid bridge reinforcement without traffic disruption.

For more on the story, read the November issue of ROADS & BRIDGES.