Seismic Retrofit of San Francisco - Oakland Bay Bridge
CLIENT
STATE OF CALIFORNIA- DEPARTMENT OF TRANSPORTATION ( CALTRANS)
MAIN CONTRACTOR
CALIFORNIA ENGINEERING CONTRACTORS – MODERN CONTINENTAL JV
STRUCTURAL STEEL FABRICATOR
MITSUBISHI- JAPAN; USIMINAS - BRAZIL
CONSULTANT OF CONTRACTOR
INTERNATIONAL ENGINEERS FOR TECHNICAL CONSULTATIONS
AND A. A. ASSOCIATES – PAKISTAN
PROJECT COST
US$ 146 MILLION
Project Description
This project is to retrofit the San Francisco-Oakland Bay Bridge (SFOBB) to current seismic safety standards to provide post-earthquake “lifeline” service. As a lifeline route, the state would use the bridge to provide a high level of post-quake transportation service for emergency response and support for the region’s economy.
The original bridge span is about 60 years old. The West Span consists of twin, end-to-end suspension bridges and a three span continuous truss structure. Each deck of the bridge has five traffic lanes in each direction with no shoulders. SFOBB carries about 280,000 vehicles per day.
The seismic retrofit involves strengthening the existing bottom lateral bracing and placing new upper lateral bracing. Additionally the end posts, all the rocker posts, several chords and all the diagonals will be strengthened by installing additional plate sections and replacing the existing lacing with perforated plates. The connection of the floor beam to the chord will be strengthened to ensure its ductility.
Project Scope
IETC’s scope of work, which required referencing almost 1,500 as-built and shop-plans of the original bridge built in the 1930’s, included producing:
- Fully detailed general layout and erection drawings detailing the retrofit steel onto the existing actual as-built bridge dimensions;
- Fully detailed fabrication shop details, all drawn to exact scale to be linked to produce CNC manufacturing Data;
- Material and bolt database;
- Review of erection and detail fabrication drawings;
- Careful examination and consideration to the constructability of the detailed steel.
Almost 2000 fabrication drawings were completed to detail 17,530,000 lb. (approx. 8,000 tons) of structural steel, in a period of 13 months.
