ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/297024
T h e C a l i f o r n i a D e p a r t m e n t o f T r a n s p o r t a t i o n ( C a l t r a n s ) i s currently making improvements to Highway 1 along the rugged Big Sur Coast in Monterey County. The Pitkins Curve project site, located north of Limekiln State Park, is characterized by steep slopes high above the Pacific Ocean and is one of many geologically dynamic sections on this remarkable highway. Noted for its spectacular views of the rocky coastline, the road is both a state scenic highway and a national scenic byway. Seven graceful concrete spandrel arch bridges, rock masonry retaining walls and parapets, and drinking fountains along the 75-mile corridor form memorable features of the Carmel-San Simeon Highway Historic District. Construction of the two- lane highway in the 1920s and 1930s was a remarkable engineering feat; maintaining it in the twenty-first century is another. Besides its historical and scenic values, Highway 1 is the only direct link between numerous small communities and isolated residences dotting the Big Sur coast. The Pitkins Curve project will restore highway reliability, decrease maintenance expenditures, and improve safety for motorists and highway workers alike. To accomplish these goals, a new bridge is being constructed that addresses the challenging geologic instabilities found at the site. understanding the Risk Unstable geology and winter storms cause unpredictable and extensive landslides and rock falls at Pitkins Curve, regularly reducing or interrupting travel for months at a time, and creating significant hardship for travelers and the coastal communities. Highway restoration is generally conducted under emergency conditions, which increases the risk to highway workers, elevates costs, restricts the range of restoration methods available, and limits ways to avoid or minimize impacts to traffic movement, the economy, and the environment. Even routine management of landslides at this location is riskier and has higher maintenance costs than other locations on the Big Sur Coast Highway. Caltrans geologists and geotechnical engineers studied the slopes at Pitkins Curve, concluding that the hillside would continue to slide, rocks would continue to fall, and the highway would continue to be damaged and severed repeatedly unless mitigation measures were taken. The Solution Becomes Apparent The design selected for the Pitkins Curve Bridge is founded on geologically stable rock formations and spans the unstable slide region. The three-span, 620-ft-long structure carries two-way traffic. The structure has end spans of 154 ft 6 in. and a main span of 311 ft. The structure width at the deck level is 35 ft 6 in., with the roadway section carrying two 12-ft-wide lanes and two 4-ft shoulders. The traveled way is bounded by Type 80 concrete barriers with steel pipe hand railings affixed to the barriers for profile THE BRIDGE AT PITkINS CuRVE / HIGHWAY 1 NORTH OF LIMEKILN STATE PARK, MONTEREY COuNTY, CALIFORNIA BRIDGE DESIGN ENGINEER: California Department of Transportation, Sacramento, Calif. GENERAL CoNTRACToR: Golden State bridge Inc. (GSb), Martinez, Calif. CoNTRACToR'S CoNSTRuCTIoN ENGINEER: NRV bridge Design, Gualala, Calif. PoST-TENSIoNING SuPPLIER: CMC Rebar Company, Fresno, Calif. READy-MIX CoNCRETE SuPPLIER: Graniterock, Watsonville, Calif. A rendering of Pitkins Curve Bridge shows how the site will appear after removal of the existing road. All drawings and photos: Caltrans. The Bridge aT PiTkins Curve One Less Bend in the Road by Mike Van de Pol and Pete Norboe, California Department of Transportation 28 | ASPIRE , Spring 2012 Book_Spr12.indb 28 4/3/12 9:18 AM