San Francisco Bay Seismology

2. San Francisco Bay Seismology

3. Bay Bridge History • Bay Bridge East Span – completed in 1936 • simple span trusses and a long cantilever truss structure • October 17 -1989 – • Loma Prieta Earthquake –Magnitude 7.1 • Upper Deck Collapsed at Pier E9

7. Geotechnical Conditions • site geology varies dramatically along the alignment of the bridge • YBI structure on the western end of the bridge, all the piers will be on land and founded on rock. As the bridge alignment progresses east towards Oakland, the bedrock/Franciscan formation dips abruptly and the remaining piers overlay deep Bay mud

8. Traditional suspension bridges have towers with two main cables that tie into anchorages in the ground. After the suspender cables are attached to the main cable, the deck is hung from the cables. • Self-anchored suspension bridges differ from conventional suspension bridges because they do not require massive end anchorages. Instead, the main cables are secured to each end of the bridge deck, which carries the horizontal component of cable tension. • The end supports resist only the vertical component of tension, an advantage where the site cannot easily accommodate external anchorages.

10. SAS Plan & Elevation • Tower Height = 160 m • Deck Length = 625 m (Total) • Longest Unsymmetrical Span SAS in the world • Super Structure = 43,603,000kg

11. SAS - TOWER

12. SAS Tower

13. Tower Section Details • Tower Section made of pentagonal box sections, which taper along the height of the tower • Grade 50 steel skin plates vary from 45 mm to 100 mm • The tower is fixed to the 6.5 m deep pile cap • supported on 13 - 2.5 m diameter steel shell pipe piles filled with concrete and socketed into rock.

15. Main Cable Approx. 1 mile long made up of 17,399 steel wire strands 137 strands –Each strand 127 wires

17. Steel Roadway Boxes Under Fabrication

21. Loop Cable Anchorage Plan

22. West Anchorage Portal Frame

25. SAS International Fabrication

27. Q&A • Q&A