Exhibit Area 1
(Plaza area)
Welcome Sign [main directory]
How the Bridge Spans the Golden Gate
Bridge Aesthetics - Art Deco on a Grand Scale
Tall and Strong - The Bridge Towers
Steel, Fog, Salt, Rust, and Paint

Exhibit Area 2
(near flagpole)
How the Bridge Vibrates
Foghorns

Exhibit Area 3
(West side of Bridge near underpass)
Historic Preservation: Lattice Strut Retrofit
Historic Preservation: Isolator Seismic Retrofit

Exhibit Area 4
(inside Battery area)
History: Design and Construction of the Bridge
Suspension Cable Tension vs. Tower Height
Battery Lancaster - Defending the Golden Gate

Exhibit Area 5
(along bike path to lower parking lot)
Bridge Deck Aerodynamics
Bridge Deck Torsional Resistance Retrofit
Wind Speed and Wind Pressure

Exhibit Area 6
(near Pavillion)
LIFETILES: animated construction of the Bridge
Braille / Tactile Model of the Bridge



Project Partners

GGBHTD
Golden Gate Bridge,
Highway and Transporation District



CUREE

Consortium of Universities for Research
in Earthquake Engineering

Main Menu : Exhibit Area 3

Seismic Retrofits and Historic Preservation

SEISMIC ISOLATION

Today we know more about earthquakes than we did in the 1930s when the Golden Gate Bridge was built. Taking advantage of this new information, two retrofit strategies have been used on portions of the Bridge to protect against large earthquakes: 1) strengthening pieces of the Bridge to resist the forces associated with strong earthquakes; and, 2) making the Bridge more flexible to roll with the punch from an earthquake. Seismic isolators are devices that allow the Bridge to move in an earthquake; this movement reduces the forces that the Bridge experiences during the earthquake. You can see isolators nearby, to your left, in the underpass. The seismic isolators are the black cylinders, about three feet (one meter) in diameter.

When a bridge is rigidly connected to the ground, it directly experiences the rapid, jerky earthquake shaking. If the bridge is mounted on seismic isolators, the isolators deform back and forth during the earthquake allowing a bridge to rock back and forth, softening the vibrations that the structure experiences. When a bridge is isolated, the forces can be reduced by as much as two-thirds as compared to a non-isolated bridge.

Invented in New Zealand in the 1970s, a common type of isolator is made of layers of steel and rubber bonded together. Sometimes there is a hole in the middle in which a lead plug is inserted to increase energy absorption.

More Images

The isolator mounted here has been cut to reveal its cross-section (with layers of steel and a special type of rubber).


All images property of the Golden Gate Bridge, Highway and Transportation District (unless otherwise indicated).


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Last updated: 11.08.12