The Golden Gate Bridge has
been incorporated with all the requisite safety aspects. The effects of
enormous wind forces have been taken into account by an accurate design of the
bridge elements. The suspension cables, tower, and the anchors have been designed
to bear all probable loads.
The Golden Gate Bridge that
was completed in 1937 is a suspenseon bridge
connecting the San Francisco Bay with the Pacific Ocean. The Golden Gate Bridge
is considered to be a globally renowned representation of San Francisco and
California. It is an engineering wonder created in 4 years due to the admirable
human vision, persistence, and technical expertise. The weight of the bridge
when built was 894,500 tons, length 8,981 feet, width 90 feet, and water
clearance 220 feet. Two primary cables pass over the tower tops, and are fixed
in concrete anchorages located at each end. The length of wire in the two
primary cables is 129,000 km that was spun in six months, and is enough to go
around the world approximately 6 times.
The design of a suspension
bridge is a complicated work that needs considerable mathematical proficiency
and engineering capability. The design has multiple aspects that require
extensive deliberations since all materials deform on the application of loads.
It is essential to determine the deck movement range at numerous locations
caused due to the varying load conditions. The different load conditions are
heavy traffic, traffic with intermittent stops and movements, and reduced or no
traffic. The designer of this bridge deliberated in detail numerous engineering
factors, including the deck movement due to its weight, environment temperature
range, velocity of wind, deck sag between suspension cables, elongation of
suspension cables, etc. It may be appreciated that the engineering technology
prevalent in that era did not encompass these important features of bridge
design. Still, the Golden Gate Bridge is considered to be an engineering wonder
because of the precise engineering planning, design, and construction processes
that were applied.
The foremost engineering
problem that existed in the design of this bridge was the structure that was
exposed to withstand the high speed windstorms coming from the Pacific Ocean. Accordingly,
the bridge was designed to withstand the most improbable condition of wind at a
speed of 100 miles an hour, at which the mid-span swing could attain a maximum
limit of 27 feet. The vehicles and bridge deck weight is transmitted upwards by
the suspender rods to the major suspension cable that transfers the forces to
the anchor blocks and bridge towers. The forces from the suspender rods create
tensile forces in the major suspension cable. These are the forces that try to
elongate the cable. The major suspension cable that sags in a parabolic shape
consists of several small-diameter steel cables wound jointly to create a huge
stranded steel cable. The tensile forces from the cable create compressive
forces in the tower that attempts to compress the tower. The tower has been
designed to withstand these compressive forces without buckling. Thus, we see
that numerous design considerations were deliberated to produce a robust bridge
that could be claimed as an excellent engineering marvel.