Most of the truly impressive bridges built in California in the 1920s and 1930s were concrete. During this time, the reinforced concrete bridge was the state’s model highway structure because of the durability of reinforced concrete as a building material and the flexibility that concrete allows in the design process, as well as for its aesthetic appeal.
One such bridge is the Bixby Creek Bridge, located on State Route 1 just 18 miles south of Carmel. Built in 1932, the bridge’s main span of 330 feet makes it the largest concrete arch span in the state. Rising more than 260 feet above a steep canyon and extending more than 700 feet long, it is also one of the world’s highest single-span concrete arch bridges. A testament to the durability and beauty of concrete structures, the scenic bridge is more than 80 years old and the most photographed object along the coastal route.
Despite the amount of material required to construct the bridge, it was sourced in-state: Douglas fir timber was used in the falsework, aggregate was excavated from the surrounding area, and cement from Davenport and San Andreas was used. The creek below supplied the water for the mix. The builders minimized the bridge’s visual impact on the natural environment by using concrete that blends in with the hillside stone.
Bixby Creek Bridge is one example of how older concrete structures can be rehabilitated to meet modern-day standards. In 1998, it underwent a seismic retrofit to make it more resistant to earthquakes. The project included eliminating breather joints in the deck and stressing the deck from end to end. The deck thus acted as a large lateral diaphragm connected to the main towers and to new cast-in-drilled-hole piles at each abutment. The towers were vertically stressed and tied to new rock anchors. The arches were laterally connected to the deck. The result is an historic bridge now capable of withstanding an earthquake.
Awards and Certifications
- National Register of Historic Places