Structural Forum

San Francisco – Oakland Bay Bridge Second Crossing

By Ronald F. Middlebrook, S.E. and Roumen V. Mladjov, S.E.

The Bay Bridge is one of the grand- existing structures to new founest engineering achievements in dations using high-capacity jacks American history, as described in on barges with temporary piers. the article on page 26. However, Preserving and reusing 60,600 the recent renovation has not added a single tons (55,000 metric tons) of steel lane to relieve traffic congestion, which has a is also a significant economic and negative impact on the Bay Area and California environmental saving. economies. There is one obvious solution for the The main achievements of the problem – to build a second crossing between new crossing would be increasing San Francisco and Oakland on an alignment the trans-bay traffic capacity and approximately parallel to the original bridge. providing a bicycle lane between After initially proposing this idea, the authors San Francisco and Oakland. It completed a feasibility study. We believe that would add four new lanes to the Existing Bay Bridge and proposed second crossing. the new bridge should be a double-decker, existing five in each direction, saving 15% of the cost versus two side-by-side thus increasing the overall capacity by 80%. building simultaneously the Bay Bridge and decks and saving 50% of the shade cast on the By 2035, the Bay Area population is esti- the Golden Gate Bridge during the Great Bay. The west span should be a new suspen- mated to increase by 50% from 1990, when Depression. This project is completely within sion bridge in harmony with the existing, with the traffic congestion was already very heavy. the capability of American engineers and complementary spans up to 2500 feet (760 m); The California Department of Transportation builders; the only challenge is to persuade the east span can be a new bridge with spans (Caltrans) needed five years of planning and federal and California state transportation similar to the existing east portion, but it would design plus nearly 12 years of construction to authorities to begin working immediately be more efficient to retrofit and relocate the build just one half of a full crossing, so it is on planning and designing the new crossing. existing structures onto new foundations on obvious that we are running out of time to solve The advantages of the second Bay Bridge piles near the current alignment (see Figure). the problem. crossing are: The old existing structure is currently The estimated steel quantities for the second • Solving the traffic congestion on the planned for demolition. Saving and reusing crossing are 152,670 tons (138,500 metric current bridge; it is only one option for building this portion tons), including over 99,200 tons (90,000 • Using the most innovative techniques of the second crossing, but it seems to be metric tons) for new structures and 53,460 tons available to build a new crossing within the best. The existing east span foundations (48,500 metric tons) for retrofitted members reasonable time and cost; are the most deficient part of the old bridge, from the old east span; 78,800 tons (71,500 • Providing an additional transportation while its superstructure has performed well metric tons) for the new west crossing (includ- link at considerable materials and cost during the past 80 years of service. Our study ing the San Francisco approach and Yerba savings; makes use of effective methods of strengthen- Buena Island transition structures), and 73,850 • Completing the pedestrian/bicycle lane ing the existing trusses, such as transforming tons (67,000 metric tons) for the east cross- for the full length between Oakland the system to several continuous structures, ing, only 20,400 tons (18,500 metric tons) of and San Francisco; reinforcing or replacing some elements found which would be new steel. This project can • Setting an example for efficient use of deficient, replacing the existing concrete deck be completed in less than five years, including funding for infrastructure renovation; with orthotropic or other lightweight steel design competitions and construction. Based and, decks, etc. Such reuse is a rare opportunity on recent construction of similar bridges, the • A great opportunity for our engineers to create the much-needed second trans-bay estimated cost is $2.55B. The efficiency of and builders to revive the art of crossing faster and for less cost. the second bridge crossing is demonstrated by American bridge engineering.▪ The feasibility study proves that a new Second comparing the 152,670 tons for this entirely SFO Bay Bridge Crossing is perfectly achievable. The new west span – as a suspension or cablestayed bridge of up to 2500 feet (760 m) – is not steel structure with the 266,750 tons (242,000 metric tons) of steel used for the new east crossing replacement, which is about half as long as Ronald F. Middlebrook, S.E., can be reached at ronfranco@gmail.com. a problem for today’s construction techniques. the overall new proposed crossing and mainly Roumen V. Mladjov, S.E., can be reached Currently there are more than 40 such bridges a concrete bridge. at rmladjov@louieintl.com. with spans longer than 2500 feet. Based on our Accomplishing a second Bay Bridge crossing study, the new east span could be easily built is a challenging task, but not at all comparable with modern steel trusses and orthotropic or to the problems that our predecessors had to A similar article appeared in the IABSE other lightweight decks, or by relocating the overcome some 80 years ago, designing and Conference Rotterdam Report, May 2013.

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