Winning Combination
by Jeff L. Brown, Contributing Editor;Serial Information: Civil Engineering—ASCE, 2002, Vol. 72, Issue 5, Pg. 68-73
Document Type: Feature article
Abstract:
The complex, 4.1-mi (6.6-km) long Richmond-San Rafael Bridge across San Francisco Bay is being upgraded as part of California's $2.5-billion program for seismically retrofitting toll bridges. A variety of two-legged and four-legged frame towers support the bridge's superstructure. The chevron-braced framing of most of these towers will be replaced by eccentrically braced frames, which are designed to deform and absorb energy during a seismic event. In some cases, special moment-resisting frames will be used. The concrete columns that support the towers will be reinforced with a unique precast-concrete jacket. The foundations themselves will be strengthened using precast-concrete pile caps and large-diameter shear piles. In some locations, new micropiles will be installed within the footprint of the existing bell foundations, between the existing H-piles. The trusses that make up the superstructure will be strengthened with additional steel. The retrofit also includes isolation bearings and large viscous dampers. At the western end, the existing concrete trestle will be entirely replaced in the same alignment using a carefully planned construction sequence to minimize disruptions to traffic. The project is scheduled for completion in late 2004.
Subject Headings: Frames | Pile foundations | Superstructures | Seismic tests | Seismic effects | Reinforced concrete | Rehabilitation
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