May 27, 1937
This continues the Appeal’s review of news stories and headlines during its Sesquicentennial year.
May 27, 1937
Many details of Golden Gate Bridge are given as completion celebrated
The two towers of the Golden Gate Bridge, the completion of which is being celebrated in San Francisco, are the largest structural steel members ever assembled, and they rank among the ten tallest structures in the world. Each tower is a skyscraper in itself, rising 746 feet above the water. This is nearly as high as New York’s Woolworth Building and 313 feet higher than the Russ Building, tallest office structure on the Pacific coast. The quantity of steel in each tower compares with the amounts used in skyscrapers of similar height.
Each tower weights 22,500 tons and supports a load of 84,000 tons.
Construction of the steel work on the main span presented many new problems for the reason that the span of 4,200 feet — over four-fifths of a mile — was 700 feet longer than had ever before been attempted. The span is 220 feet, above the water at the center of the bridge and had to be constructed over the open sea.
Changes in temperature, wind velocity during storms and other extraordinary conditions had to be taken carefully into account in the design and construction.
Allowance is made for a sideway of more than 20 feet in either direction at the center of the main span. The bridge has a safety factor of 2.6 at a wind velocity of 90 miles per hour, whereas the highest velocity ever recorded at the golden Gate is only 58 miles an hour. Allowances also had to be made for the fact that the deck of the bridge will be raised or lowered as much as 10 feet by expansion and contraction due to extreme changes in temperature and loading.
The two cables supporting the deck are each 7,700 feet long and are 36 1/2 inches in diameter. Each contains more than 27,000 separate wires. The wire used in spinning the cables totaled 80,000 miles, sufficient to girdle the earth more than three times.
The bridge measures 6,450 feet over all and comprises a main span of 4,200 feet between the two towers, and two side spans of 1,125 feet each. The 90 foot deck provides for six traffic lanes and two sidewalks, each 11 feet wide. The entire bridge contains enough steel to load a freight train 20 miles long.
Although fabricated sections ranged in weight from 45 to 80 tons each and enough rivets to stretch 36 miles of laid end-to-end were used to fix them in place, the work was organized and carried through with such precision that construction of the tower of the San Francisco side was completed 104 days ahead of schedule.