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Golden Gate Bridge | The CRAZY Engineering behind it

 


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 linked 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 over 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 an area of serpentine rock only 20 inches (508 millimeters) square. The rock was more than strong enough.

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Early design, dubbed as "ugly" by the local press, called for heavy-looking cantilevered structures jutting out from the towers.
 


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.)

Engineering the Design - Logo from 1933 Logo of the Golden Gate Bridge and Highway District as of 1933 from the Golden Gate Bridge, Highway and Transportation District - The picture of the Bridge in the logo is of the first cantilever-suspension design; the final design was an all-suspension bridge design.
Engineering the Design - Sources of steel Sources of the steel used in the Golden Gate Bridge from the Golden Gate Bridge, Highway and Transportation District - A letter from McClintic Marshall Corporation, a subsidiary of Bethlehem Steel Corporation, dated April 28, 1933, detailing where the steel for the Bridge was fabricated. Not included are the cables, which were part of the Roebling Son's Company contract.
Engineering the Design - Letter by Andrew C. Lawson Letter by Andrew C. Lawson, examination of rock for foundation of South Tower from the Golden Gate Bridge, Highway and Transportation District - A letter from consulting geologist Andrew C. Lawson to Joseph Strauss, Chief Engineer; "When struck with the hammer it rings like steel, significant of its sound highly elastic condition…. [I am] confirmed in my opinion as to the integrity of the rock and the ample stability of the foundation."
Engineering the Design - Getting down to bedrock Getting Down to Bedrock from the Golden Gate Bridge, Highway and Transportation District - A newspaper article from the February 14, 1930 San Francisco Examiner picturing Charles Derleth, O.H. Ammann, Andrew C. Lawson, and Joseph Strauss looking at boring samples.
Engineering the Design - Engineers speed plans Engineers Speed Plans for Golden Gate Bridge from the Golden Gate Bridge, Highway and Transportation District - A newspaper article from the March 1930 Pacific Street and Road Builder; an artist's conception of the original design (combined cantilever-suspension bridge) that was later rejected in favor of an all-suspension design.
Engineering the Design - Western Construction News Proposed Golden Gate Bridge from the Golden Gate Bridge, Highway and Transportation District - An artist's illustration of the planned Golden Gate Bridge from the September 10, 1930 Western Construction News. The suspension bridge is pictured as it was eventually built; the somewhat grand design for buildings and plazas that are pictured at the two ends of the Bridge were not built.
Engineering the Design - Borings started for Gate span Borings Started for Gate Span from the Golden Gate Bridge, Highway and Transportation District - A newspaper article from the November 29, 1930 Vallejo California Chronicle, Sebastopol California Times, and Cresent City Triplicate with photos of the diamond-tipped drills used to bore into the rock at the San Francisco end of the Bridge, next to Fort Point, to extract rock samples.
Engineering the Design - Strauss made Chief Strauss Made Chief in Work of Spanning Bay to Marin from the Golden Gate Bridge, Highway and Transportation District - A newspaper article from the August 16, 1929 San Francisco Chronicle reporting that Joseph Strauss was



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