Seismic Retrofits and Historic Preservation


Much has been learned about earthquake engineering since the Bridge was designed and built in the 1930s. Today, mathematical analysis techniques help calculate how a structure will perform when subjected to various levels of ground shaking. In addition, physical tests are run on specimens that represent portions of the structure. Comparing and validating mathematical analysis with test results is a standard engineering method.

To test the strength of an existing bridge piece called a lattice strut on the Golden Gate Bridge, a large replica was made and tested by the University of California at Berkeley Civil and Environmental Engineering Department. A piece of that bent and buckled test specimen is displayed here. With accurate figures for the strength of these pieces, decisions can be made to replace or strengthen particular portions of the Bridge to preserve it against damage in future earthquakes.

The original lattice struts have a crisscross pattern of many small pieces of steel riveted together. When one of these struts is replaced, the new, stronger, one-piece steel member has holes cut in it to preserve the historic appearance of the Bridge.

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The U.C. Berkeley structural testing machine is three stories tall and can compress or push down on a specimen with a force of 4 million pounds (17.8 meganewtons).

credit: University of California at Berkeley

 


The replica of a steel lattice strut of the Bridge was tested in compression until it buckled, to measure its strength.

Photo by A. Astaneh-Asl (UC Berkeley)

 

Explore this Topic Further

Seismic Retrofit of the Golden Gate Bridge

Overview of Golden Gate Bridge Seismic Retrofit Construction Project (grade 6 to adult)
On this web site the Golden Gate Bridge, Highway and Transportation District (GGBHTD) summarizes the timeline, phases of design and construction, as well as the reasoning behind the bridge seismic retrofit program. The Golden Gate Bridge Seismic Retrofit Phase II was named the recipient of the 2007 Outstanding Civil Engineering Achievement (OCEA) Award by the American Society of Civil Engineers.

Isolator Seismic Retrofit (all ages)
This exhibit, in the visitor area at the San Francisco end of the Bridge, describes how seismic isolators have been installed to reduce the movement of the approach spans to the Bridge in an earthquake.

Animation of the Golden Gate Bridge in an Earthquake created by Computers & Structures, Inc. (all ages)
This animation exaggerates the motions of the types of vertical, horizontal and twisting vibrations that the Golden Gate Bridge would experience in a repeat of the 1906 earthquake. (20 second video)

Seismic Retrofit of the Golden Gate Bridge by Tim Ingham, Santiago Rodriguez, Marwan Nader, & Fabio Taucer, 1996 (adult)
This conference paper written by engineers at T.Y. Lin International gives an overview of the seismic retrofit of the Golden Gate Bridge, including ground motions, design criteria, analysis methodology, installation of viscous dampers, and retrofit of the lateral bracing, towers, piers, cable saddles, wind-locks, and deck.

Seismic Retrofit of the Towers of the Golden Gate Bridge by Marwan Nader & Tim Ingham, 1996 (adult)
This technical conference paper written by engineers at T.Y. Lin International discusses in detail the procedures and design methods used to retrofit the towers that support the Golden Gate Bridge.

Seismic Protective Systems for the Stiffening Truss of the Golden Gate Bridge by Santiago Rodriguez & Tim Ingham, 1996 (adult)
This conference paper written by engineers at T.Y. Lin International summarizes the design of the seismic retrofit of the Golden Gate Bridge stiffening trusses. The paper discusses the analysis method, the modeling techniques, and the seismic response of the bridge.

Replacing Lattice Struts the Golden Gate Bridge, Highway and Transportation District (GGBHTD)
The original struts ("lattice struts") of the Bridge were composed of many small pieces of steel riveted together. When some had to be replaced with new, stronger ones as part of the seismic retrofitting of the Bridge, larger single pieces of steel were used, but with laser-cut holes in them to look like the originals.

Lattice Strut Seismic Testing the Golden Gate Bridge, Highway and Transportation District (GGBHTD)
A full-scale replica of an original riveted structural member of the Bridge was tested at U.C. Berkeley to experimentally verify its strength, allowing engineers to calibrate their seismic retrofit calculations.

Earthquakes

Latest Earthquakes from US Geological Survey (all ages)
This interactive continuously-updated map provides location and magnitude information for earthquake occurring all over the world. The map defaults to showing only the earthquakes that occurred in the last day. If you would like to see a longer history, click on the gear in the upper right hand corner and select a longer time span of 7 or 30 days.