Architectural Importance of the Golden Gate Bridge

Architectural Importance of the Golden Gate Bridge
Institution
Date
Part 1
Golden Gate Bridge served as the principal component of the only highway connecting San Francisco with the countries to its north. It is considered as one of the western civilization’s greatest achievements. The bridge is a unique architectural structure consisting of a 1280 m main span and two 343 m side spans. These spans suspend from two continuous 924 mm diameter steel wire cables spaced at 27.4 m. Cables supported on steel towers, and then anchored in concrete anchorage blocks. More than one million tons of concrete was used to build the anchorages. The towers consist of two thin steel beams that are braced together with struts. The 210m towers consist of tall, thin steel beams braced with struts. Above the roadway, the beams are braced by trussed portal struts. Below the roadway, they are braced by double diagonal struts. Cast steel saddles at the top of the shafts secured the cables to the shaft. In addition, a weak connection between the steel tower and the reinforced concrete was provided to resist wind loads during construction. Shear plates welded to a 127mm thick base plate were riveted to the tower plates.
The tower shafts were modeled using two and three-node 3-dimensional elastic beam elements with shear deformations. The tower struts were modeled using beam elements with shear area equivalent to the actual laced members. The tower struts connections were modeled using rigid constraints of dimensions similar to that of the joints. The gusset plates connecting the individual strut members were also modeled using their corresponding section properties. The tower plinth was modeled using membrane elements with a simple elastic-plastic material. Towers fixed about the longitudinal axis of the bridge enabled the rotation, and the membrane elements were connected to the reinforced concrete piers with gap elements to allow for uplifts.
Steel dowels embedded in the pier restrained sliding of the base plates. The suspended structure consists of two 7.6 m deep stiffening trusses spaced at 27.4 m. The stiffening trusses are connected with top and bottom lateral bracing systems. The orthographic deck and the sidewalks are carried by floor beams that are spaced at 7.6 m. Fandel (2006) say, “The north pier, which supports the tower, was built quickly on a bedrock ledge 6m below the water. But on the southern San Francisco side, Joseph Strauss (Project Engineer) had to build his pier in the open ocean, 30m below the surface. He built an enormous watertight cofferdam and pumped in hundreds of ton of concrete. By 1935, the towers were complete, and cable-spinning began”1. Still, Steel frame and steel cables played a critical role in the construction of the Golden Gate Bridge. “The fabricated steel used in the construction of the Golden Gate Bridge was manufactured by Bethlehem Steel in plants, in Trenton, New Jersey, and Sparrow Point. The shipment of the steel was timed to coincide with the construction of the bridge. Cable spinning began in October 1935. To create the cables, Roebling developed a method called parallel wire construction. The innovative technique enabled a cable of any length and thickness to be formed ...