SEISMIC DESIGN OF THE SKYWAY SECTION OF THE NEW SAN FRANCISCO-OAKLAND BAY BRIDGE (ABSTRACT ONLY)

The seismically vulnerable eastern span of the San Francisco-Oakland Bay Bridge will be replaced with a dual, 3.5-km long parallel structure. The bridge will be situated between the Hayward and the San Andreas faults, which can generate large earthquakes. Performance criteria require that the bridge be operational following a 1500-year return period earthquake from either of these two faults. The middle 2.0 km of the new bridge consist of a segmental concrete "skyway" with spans varying from 96 to 160 m in length. This will be constructed using the balanced cantilever method of segmental construction. The superstructure is a box girder 9 m deep at the pier and 5.5 m deep at midspan. The box is 25 m wide and designed to carry either 5 lanes of highway traffic with standard shoulders or 4 lanes of traffic with a light rail system. Mid-span hinges between longitudinal frames allow longitudinal expansion and contraction due to creep, shrinkage and temperature changes. An internal steel beam assembly at the hinge provides shear transfer and moment resistance in addition to controlling deflections at the cantilever end of each frame. A typical footing is supported by six 2.5 m diameter battered piles. The average length of these piles is about 100 m. They consist of driven steel shells with a composite reinforced concrete fill in the upper section. The design of the pile caps is based on capacity design principles. In order to transfer the over-strength moments from both the pier and the piles, they are to be constructed from (concrete encased) structural steel. The piers are box shaped and sculpted to architecturally match the main pylon of the signature suspension bridge. The typical dimensions are 6.5 m x 8.5 m. The main reinforcement is placed in the four corners of the box; heavy confinement is provided with closely spaced hoops to ensure ductile behavior. The pier is the most critical element in the bridge from a seismic design standpoint; it is the only element designed to yield and form plastic hinges during a safety evaluation earthquake. The design approach was to adopt a stiff foundation system thereby controlling pile cap elastic displacements to acceptable levels and minimizing the potential for permanent pile cap offsets. A relatively stiff foundation system was achieved through the use of large diameter battered piles.

• Corporate Authors:

  Multidisciplinary Center for Earthquake Engineering Research

  State University of New York, 107 Red Jacket Quadrangle, P.O. Box 610025
  Buffalo, NY  United States  14261-0025
• Authors:
  • Maroney, B
  • Abbas, S
  • Sah, M
  • Houlahan, G
  • Ingham, T
• Conference:
  • Third National Seismic Conference and Workshop on Bridges and Highways: Advances in Engineering and Technology for the Seismic Safety of Bridges in the New Millennium
  • Location: Portland, Oregon
  • Date: 2002-4-28 to 2002-5-1
• Publication Date: 2002-3-11

Language

• English

Media Info

• Pagination: p. 107

Subject/Index Terms

• TRT Terms: Batter piles; Beams; Bearing capacity; Box girders; Bridge piers; Bridge superstructures; Earthquake resistant design; Footings; Hinges; Pile caps; Segmental construction; Steel; Structural steel; Suspension bridges
• Identifier Terms: San Francisco-Oakland Bay Bridge
• Subject Areas: Bridges and other structures; Design; Highways; I24: Design of Bridges and Retaining Walls;

Filing Info

• Accession Number: 00933586
• Record Type: Publication
• Files: TRIS
• Created Date: Nov 1 2002 12:00AM