T.Y. Lin International (TYLI), a globally recognized, full-service infrastructure consulting firm, announces that the Laurel Street Overcrossing/Cabrillo Bridge Seismic Retrofit and Rehabilitation Project in San Diego, California, has won the 2017 Seismic Safety Award from the California Department of Transportation (Caltrans). TYLI was selected by Caltrans to upgrade the historic bridge to current earthquake safety standards. Scope of work included performing detailed inspections; determining the scope and cost of necessary rehabilitation work; developing the seismic retrofit strategy; preparing final plans, specifications, and estimate (PS&E), and providing support during construction for both the rehabilitation and seismic retrofit. The Seismic Safety Award is given by the Caltrans Seismic Advisory Board and honors the best of California’s transportation projects, with emphasis on seismic safety. The project was completed in May 2015.
Resembling a Roman aqueduct, the Laurel Street Overcrossing at State Route (SR) 163, also known as the Cabrillo Bridge, was constructed in 1915 and is listed on the National Register of Historic Places. The 769-foot-long, reinforced concrete cantilevered hollow arch structure provides access to Balboa Park for vehicles, bicycles and pedestrians, and links travel to Sixth Avenue, a parallel arterial of SR 163. Over 100,000 vehicles travel this portion of SR 163 under the bridge each day, providing access for tourism to Balboa Park, one of San Diego’s main visitor destinations.
An innovative seismic retrofit strategy was developed using both response-spectrum and non-linear time history analyses. Since the superstructure and substructure are hollow cell structures, TYLI was able to preserve the historic character of the bridge by concealing all retrofitting within the internal framework. Retrofit measures included locking the midspan expansion joints through longitudinal post-tensioning of the superstructure, improving the transverse seismic behavior. The piers were strengthened by adding vertically post-tensioned shear walls, which extend from the foundation into the superstructure and provide sufficient shear and displacement capacity for the design seismic event.
Project challenges included maintaining pedestrian access on the bridge during construction and limiting bridge closure to traffic to a short, four-month window. TYLI developed several construction stages to facilitate openings in the bridge sidewalks for the pier and superstructure post-tensioning operations and reconstruction of the deck joints.
“Our goal was to improve the structural integrity of the Laurel Street Overcrossing/Cabrillo Bridge in order to ensure the safety of the traveling public while preserving the architectural distinctiveness of this important San Diego landmark,” said Mark Ashley, P.E., TYLI Senior Vice President and West Region Director. “T.Y. Lin International is honored to share the 2017 Seismic Safety Award with the City of San Diego and the Caltrans team.”
In addition to the 2017 Seismic Safety Award, the Laurel Street Overcrossing/Cabrillo Bridge Seismic Retrofit and Rehabilitation Project has also won the 2015 Outstanding Centennial Historic Engineering Project Award from the American Society of Civil Engineers, San Diego Section; the 2015 Project of the Year Award from the American Public Works Association, San Diego and Imperial Counties Chapter; the 2015 Public Project of the Year from the Society for Marketing Professional Services, San Diego; and the 2015 Build San Diego Award, Heavy/Highway Construction, from the Associated General Contractors of America, San Diego Chapter.
Photo: Peter Smith (TYLI Senior Bridge Engineer) and Malcolm Dougherty (Caltrans Director)
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