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Photographer's Note

A closer view of the fifth largest dome in the world.

The city hall is vast, totalling over 500,000 square feet (46,000 mイ) and occupying two full blocks of San Francisco. Its dome, which owes much to Mansart's dome of Les Invalides, Paris, is the fifth largest dome in the world, rising 307.5 feet (94 m) above the Civic Center national historic district. It is fourteen inches (356 mm) higher than the United States Capitol.

The Loma Prieta earthquake of 1989 damaged the structure, and twisted the dome four inches (102 mm) on its base. Afterwards work was undertaken to render City Hall earthquake resistant through a base isolation system. In an earthquake, the mass of the dome acts as a pendulum, rocking the building's structure and tearing it apart. The base isolation system of hundreds of rubber and stainless-steel insulators inserted into City Hall's underpinnings has the effect of disrupting seismic waves before they can affect the structure. As of 2002 San Francisco's City Hall is the world's largest base-isolated structure預 triumph of seismic retrofitting.

All photographs of this City Hall Series were photographed using RAW-NEF format.

The WORKSHOP shows a cross section of this dome.

PP Work: Adjust levels control; Adjust saturation; Sharpen; Crop; Reduce image size for upload.

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Additional Photos by Andre Salvador (erdna) Gold Star Critiquer/Gold Star Workshop Editor/Gold Note Writer [C: 738 W: 81 N: 1094] (5713)
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