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.
Table 2. Golden Gate Bridge Natural Frequencies
Mode Type

Period of vibration (sec)

Natural Frequency (Hz)

Transverse

18.2

0.055

Vertical

10.9

0.092

Longitudinal

3.81

0.262

Torsional

4.43

0.226


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:
