Safeguarding Bixby Bridge

The two-lane arch bridge over Bixby Creek—in Big Sur, California—reflects the Art Deco style popular in the early 1930s, when the crossing was built. Its slender deck and arch ribs appear almost transparent as it carries U.S. Route 1 through the scenic park. But the bridge was vulnerable to a major earthquake, so the California Department of Transportation hired Buckland & Taylor of Walnut Creek, California, to design a seismic upgrade that would allow the bridge to withstand the most violent earthquake with not collapse and no loss of life, and which would also preserve the bridge’s appearance and do minimal damage to the surrounding ecosystem. The crux of the design was the longitudinal posttensioning of the entire bridge deck from end to end. Now the continuous, stiffened deck has four lateral reaction points: two new massive abutments anchored by large-diameter cast-in-drilled-hole (CIDH) piles and the two towers strengthened and anchored to rock with tie-down anchors. New shear keys laterally support the arch ribs at their crowns by linking them with the deck.