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/740919
PROJECT Rehabilitation and Seismic Retrofit of the North Torrey Pines Road Bridge by Keith Gazaway, Nathan Johnson, and Mark Creveling, Kleinfelder Inc. Situated along the scenic coastline at the northern border of San Diego, Calif., the North Torrey Pines Road Bridge is a landmark structure valued by the local community of Del Mar for its historical significance and aesthetic appeal. Until recently, the iconic structure was slowly succumbing to corrosion and was highly susceptible to seismic damage. In 2000, the city of Del Mar bought the bridge for $1 from the city of San Diego when the two cities could not agree on whether to repair or replace the bridge. Now, the city of Del Mar, with help from the Federal Highway Administration (FHWA) and local transportation funding sources, has infused this 83-year-old landmark with new life and strength to maintain its beauty for at least 50 more years. It will remain one of the more significant historic examples of cast-inplace concrete bridges on the coast of California. Apparent Deficiencies The original 550-ft-long bridge superstructure consisted of 15 simply supported T-beam concrete girder spans on multi-column bents ranging in height from 30 to 70 ft. Most of the bents are normal to the roadway, but where the bridge crosses over the active railroad at a 63-degree skew, complex geometry requires several bents to be conjoined, resulting in a stiff network of columns and railroad collision walls. In the early 1990s, the California Department of Transportation (Caltrans) added the bridge to the statewide federally mandated seismic retrofit program, and subsequently identified it as structurally and seismically deficient and functionally obsolete. As of 2008 it had a bridge sufficiency rating of 19 out of 100, which was mostly attributed to severe and extensive corrosion throughout the superstructure and substructure due to the coastal environment. Suffering from Corrosion Although much corrosion damage was plainly visible, an exhaustive investigation and materials evaluation of the bridge was warranted including delamination surveys, material sampling and testing, nondestructive and destructive testing, and continuity (next page) PROFILE NORTH TORREY PINES ROAD BRIDGE / DEL MAR, CALIFORNIA BRIDGE DESIGN AND GEOTECHNICAL ENGINEER: Kleinfelder Inc., San Diego, Calif. CONSTRUCTION MANAGER: T. Y. Lin International, San Diego PRIME CONTRACTOR: Flatiron West, San Marcos, Calif. PRECASTER: Oldcastle Precast, Perris, Calif.—a PCI-certified producer POST-TENSIONING CONTRACTOR: DYWIDAG-Systems International, Long Beach, Calif.