1931: Golden Gate Bridge – San Francisco, CA
Innovation: Suspension bridge (cable technology)
Location: San Francisco, California
By: Charles Ellis (Engineer), John Roebling and Sons (Cable Manufacturer)
While constructing the Golden Gate Bridge, many innovations in technology arouse due to the visionary project. The most important one became the cable technology involved in the bridge, which uses the largest bridge cables ever made, long enough to encircle the world more than three times at the equator. After calculating the dip forces, the cables had to be super flexible, strong enough to support the weight of the bridge, and had to be constructed on-site. John Roebling and Sons met the requirements by a construction process they called Parallel Wire Construction. This technique enabled any cable of any length and thickness to be created by binding thinner wires together. Many wires the diameter of a pencil were bound together into strands, which then were compressed by a hydraulic jack to make a cable. Each of the two main cables has over three feet in diameter, 7,659 feet long and contains 27,572 parallel wires. One wire at a time, the cables for the Golden Gate bridge were spun from tower to tower, anchorage to anchorage. The work had to be performed in a precise sequence in order to create the balance needed for the cables to absorb the proper amount of wind pressure.