GOLDEN GATE BRIDGE

Figure 1. Golden Gate Bridge

The Golden Gate Bridge was completed in 1937. Joseph B. Strauss was the chief engineer. It is located on Interstate 101 between San Francisco and Marin Counties.

The weight of the bridge is 419,800 tons including suspended structure, towers, piers and fenders; but not including anchorages and north and south approaches. The equivalent mass is 3.808 (10^8) kg.

The Golden Gate Bridge is a suspension bridge. It is constructed of steel. Key dimensions are given in Table 1.

The bridge is mounted on concrete piers which extend down to bedrock.

Table 1. Golden Gate Bridge Dimensions  Dimension  meters  feet  Total Length  2740  8980  Suspended Span Length(Distance between Towers)  1280  4200   Tower Height  228  748  Span Height above Strait  67  220  Height of each Tower above Roadway  152  500  Width  27.4  90

In addition to traffic loading, the Golden Gate Bridge must withstand the following environments:

1. Earthquakes, primarily originating on the San Andreas and Hayward faults.
2. Winds of up to 70 miles per hour.
3. Strong ocean currents.

The Golden Gate Bridge has performed well in all earthquakes to date, including the 1989 Loma Prieta Earthquake. Several phases of seismic retrofitting have been performed since the initial construction.

Note that current Caltrans standards require bridges to withstand an equivalent static earthquake force (EQ) of 2.0 g.

The retrofit measures have focused on keeping the Bridge open to emergency vehicles immediately following a major earthquake and to all traffic within one month.

Seismic analysis of the bridge must account for the bridge's natural frequencies. The natural frequencies are shown in Table 2, as taken from Reference 1.

Reference

1. Anil K. Chopra, Dynamics of Structures: Theory and Applications of Earthquake Engineering Prentice Hall, 1996.

Video of the Construction of the Golden Gate Bridge, as well as other famous bridges:

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