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Overview

Engineer T.Y. Lin working with Skidmore Owings and Merrill architect Myron Goldsmith produced this innovative bridge design, that was to cost a mere $13 million in 1977. A cable-suspension bridge, the solution avoided the erection of costly suspension towers, that would have needed to be 350-feet high. Instead, Lin and Goldsmith proposed anchoring the suspension cables on the gorge's cliffs themselves, cutting costs and improving seismic performance. This solution also made support of the bridge's curved roadbed easier than a more conventional towered design.

Building History

Engineer and architect Myron Goldsmith (1918-1996) of Skidmore, Owings and Merrill, Architects, Chicago Office, conceived this project with noted CA bridge engineer T.Y. Lin (1912–2003) to span the American River's Middle Fork in the California Gold Country. It was to have been situated 10 miles upstream of the US Reclamation Service's Auburn Dam. Goldsmith and Lin had a difficult site with which to work. The American River at this point was broad and deep and had steep embankments on both sides; additionally, the bridge had to withstand seismic tremors common to the Auburn area. To construct a straight, conventional bridge design would have required costly alterations to the landscape along both banks, including tunneling. To obviate site and cost constraints, Goldsmith and Lin produced a bridge plan that had a arcing bridge deck hung from 80 steel cables mounted to points along both hillsides.

According to SOM's web site: "The design had a number of advantages, including the fact that the cables could be easily post-tensioned to control stresses and strains, while being anchored in the hillside in a manner that would regulate pressure on the curved steel and concrete girders. Moreover, tests showed that the curved design was particularly effective in dealing with earthquakes and high winds." (See "Ruck-a-Chucky Bridge,"accessed 05/09/2014.) Another web site explained the bridge's design advantages: "To avoid the need for any piers, a 'hanging arc' design was developed. It curves 50 degrees along a 1,500-foot radius in a length of 1,300 feet. The deck edges are supported by cables that are anchored on the slopes of the river valley. The cables are arranged in a position that produces an axial line of pressure in the curved girder. They are post-tensioned to control stresses and strains and achieve an ideal condition of almost no bending or torsional moment in the girder." (See OPAC Consulting Engineers.com. "Ruck-A-Chucky Bridge, Auburn, California," accessed 08/19/2019.)

Richard Stepler, writing in Popular Science, said of the bridge in 1977: "The design of this bridge is as awe-inspiring as its location: a 1400-foot-deep gorge in Northern Califonria. And the engineering is as practical as it is spectacular. Spanning a reservoir due to be created at the site in the 1980s, the Ruck-a-Chucky Bridge (it's named for a stretch of rapids in the Middle Fork of the American River) works with the environment. With the bridge's 45 degree curve, approach roads can gradually descend the gorge's steep sides. If the bridge were straight, extensive excavation would be necessary. The extremely steep slopes of the gorge provide support for the bridge: suspension cables are anchored to the hillsides high above, rather than hung from towers. Cable-hung bridges are nore like to survive earthquakes--and the area is seismically active." (See Richard Stepler, "Bridge with a Twist," Popular Science, vol. 210, no. 6, 06/1977, p. 90-91.)

Building Notes

Unbuilt.

Mark Ketchum, who worked as a Design Engineer for T.Y. Lin International, "...performed all dynamic analyses for both the steel and concrete design alternatives" for the bridge's design team. (See OPAC Consulting Engineers.com. "Ruck-A-Chucky Bridge, Auburn, California," accessed 08/19/2019.)

PCAD id: 14246