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San Francisco in San Francisco City and County, California — The American West (Pacific Coastal)
 

Engineering the Design

 
 
Engineering the Design Marker image. Click for full size.
By Duane and Tracy Marsteller, July 3, 2021
1. Engineering the Design Marker
Inscription.  In 1921, engineer Joseph B. Strauss submitted a design for a bridge that would cross the Golden Gate Strait — a hybrid bridge with a suspension span supported at each end by cantilever trusses. By 1929, consulting engineers Leon S. Moisseiff and O.H. Ammann had persuaded Strauss to accept the more graceful all-suspension bridge design that we see today.

Strauss assigned engineer Charles A. Ellis to work in collaboration with Moisseiff to perform the calculations needed to complete the design, which was complex and challenging work done without modern computers. The most common “calculator” that structural engineers used in that era was a slide rule, and drafting was done with pencil and paper on drawing boards.

The engineers relied on recent advances in suspension bridge design theory. They verified those calculations with tests on a steel tower model of 1:56 scale (56 times smaller than one of the actual towers). The tests confirmed that the tower calculations were sound.

The geology of the south tower location was investigated before construction could begin. The south tower was planned for construction more than
Engineering the Design Marker image. Click for full size.
By Duane and Tracy Marsteller, July 3, 2021
2. Engineering the Design Marker
Marker is second from left.
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1,100 feet (335 meters) offshore on serpentine rock. Consulting geologist Andrew C. Lawson oversaw a load test performed by placing weight equivalent to a fully loaded railroad boxcar on a square shaped area of serpentine rock 20 inches by 20 inches (508 millimeters). The rock was more than strong enough.

Captions:
Left: A model of one of the Bridge towers was loaded in a civil engineering testing machine at Princeton University in 1933. One test, with a scaled-down force, simulated the actual 120 million pounds (54 million kilograms) of vertical load that would be placed on the top of each full-sized tower by the main cables. (To visualize that much weight, picture a large ocean liner.)
Top right: This early design, dubbed as "ugly” by the local press, called for heavy-looking cantilevered structures jutting out from the towers.
Bottom right: The Bridge as it looks today.
 
Erected 2012 by Golden Gate Bridge Highway and Transportation District.
 
Topics. This historical marker is listed in these topic lists: Bridges & ViaductsScience & Medicine. A significant historical year for this entry is 1921.
 
Location. 37° 48.488′ N, 122° 28.548′ W. Marker is in San Francisco, California, in San Francisco City and County. Marker can be reached from Coastal
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Trail. Marker is in the Battery Lancaster exhibit area of the Golden Gate Bridge Vista Point South overlook. Touch for map. Marker is in this post office area: San Francisco CA 94129, United States of America. Touch for directions.
 
Other nearby markers. At least 8 other markers are within walking distance of this marker. Making the Impossible, Possible: The Story of the Golden Gate Bridge (here, next to this marker); Bridging the Gate — the Beginning (here, next to this marker); A Bathtub for the South Tower (here, next to this marker); Working Under Water (here, next to this marker); World's Tallest Bridge Towers (here, next to this marker); Fort Point Arch (here, next to this marker); Spinning the Main Cables (here, next to this marker); Hanging the Roadway Deck (a few steps from this marker). Touch for a list and map of all markers in San Francisco.
 
Additional keywords. Golden Gate Bridge
 
 
Credits. This page was last revised on July 15, 2021. It was originally submitted on July 6, 2021, by Duane Marsteller of Murfreesboro, Tennessee. This page has been viewed 36 times since then. Photos:   1, 2. submitted on July 6, 2021, by Duane Marsteller of Murfreesboro, Tennessee.

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Dec. 1, 2021