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Repairing the Oakland Bay Bridge



The devasting 1989 Loma Prieta earthquake caused vast destruction in the San Francisco Bay area. One of its effects included the collapse of a section of decking in the east span of the San Francisco-Oakland Bay Bridge. The quake prompted a series of studies to determine the seismic safety of California’s bridges. As a result of study findings, in 2002, construction began on the new Bay Bridge. The west span (San Francisco side) was able to be retrofitted through reinforcement, but the east span (Oakland side) needed to be replaced entirely, with its new design including the world’s longest self-anchored suspension span (SAS). The Bay Bridge project is one of the largest public works projects in U.S. history.

The many parts of this project were performed via multiple contracts. Engineering firms American Bridge and Fluor formed a joint venture (referred to as ABFJV) to construct the 625-meter-long SAS. While the span’s single cable suspension system presented a construction challenge that garnered much press, other state-of-the-art engineering systems also made their debut in this project. Covering the east span’s hinge pipe beams is a specially constructed seismic joint which allows the bridge to expand and contract up to 1 meter, while still keeping the frames solid.

Because of the variety of materials being used, the typical cement set time of 28 days was impractical. The steel suspension bridge can experience expansion of up to 3 inches in a single day, so the cement used at joints on the bridge needed to set within a four-hour time window. Rapid Set® cement was used at the seismic joints on either side of the SAS so the concrete could set and achieve sufficient strength before bridge movement occurred. The fast-setting hydraulic cement offers low-shrinkage and excellent durability.
Precision Concrete Materials produced the concrete using Rapid Set cement. Four bridge hinge locations (two in the eastbound lanes and two in the westbound lanes) incorporated this high early-strength material. Three volumetric mixers provided continuous and consistent concrete. (A fourth volumetric mixer remained onsite as part of the contingency plan for the project.) Finishing techniques included the use of mechanical vibrators, hand screeding and hand finishing. Curing techniques included the use of curing compound and burlene.

Concrete compression tests were performed on the fast-setting hydraulic cement mix at joint segments in time intervals of one, seven and 56 days. All of the test results proved that the concrete strengths exceeded performance requirements, and did so in a shorter time frame than was specified.

On September 2, 2013, the new east span opened to traffic. After almost six years of around-the-clock construction, the bridge combines an enormous number of state-of-the-art engineering techniques. Cutting-edge technologies, including the use of rapid-setting cement, helped the San Francisco-Oakland Bay Bridge reach groundbreaking accomplishments and stay on schedule for an on-time opening.



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