| Key Facts |
| Bridge Name | Facility Carried / Feature Intersected | Location | Structure Type | Construction Date / Builder or Contractor | |
|---|---|---|---|---|---|
| ! |
San Francisco Oakland Bay Bridge
| I-80 Over San Francisco Bay | San Francisco and Oakland: San Francisco County, California and Alameda County, California | Metal Deck Truss Stiffening Cable Suspension, Fixed | 1936 By: American Bridge Company of New York, New York |
| Technical Facts |
| Rehabilitation Date | Main Span Length | Structure Length | Roadway Width | Main Spans | Approach Spans |
| 1962 | 2310 Feet (704.1 Meters) | 22655 Feet (6905 Meters) | 58 Feet (17.7 Meters) | 9 | 100 |
Note: This bridge has not yet been photo-documented/inspected by the HistoricBridges.org team. Narratives and photos offered are derived from findings on the internet.
This bridge is located far beyond the HistoricBridges.org team's current area of coverage as dictated by limitations in time and funding. However, this bridge has global significance and it is also critically important to understand and discuss this bridge in order to create a clearer context and understanding of various bridges that have been visited and documented by the HistoricBridges.org team in North America. As a result, HistoricBridges.org is offering photos of this bridge from legally available internet sources in order to facilitate the narrative and discussion offered below.
|
Excerpts From Historic American Engineering Record The San Francisco-Oakland Bay Bridge is one of the most impressive engineering structures in the United States. The bridge has been recognized by the American Society of Civil Engineers as a nationally significant structure from the standpoint of engineering as well as its importance in the transportation history of California and the nation. The Bay Bridge was the longest bridge in the world at the time it was built. It is also among the world's most complex bridges in that it incorporates a variety of different bridge types connected to form a single structure carrying two levels of traffic between San Francisco and Oakland, California. People may disagree as to whether the Bay Bridge is more important for its engineering, its role in transportation history or for its importance in the politics of the area. The structure is highly significant in all of these different ways. |
Completed one year before the Golden Gate Bridge, The San Francisco Oakland Bay Bridge, locally known as simply the Bay Bridge, is actually a complex system of unique and independent structures, with the largest features including suspension spans crossing the portion of the bay west of Yerba Buena Island, a tunnel on Yerba Buena Island, and cantilever truss spans east of Yerba Buena Island.
The Historic American Engineering Record found that the Bay Bridge transcended the world of bridges, instead describing it not only as one of the most important bridges in the country, but indeed one of the most impressive and significant structures of any kind in the entire country. No other bridge has been documented so extensively and completed by the HAER project, the documentation containing over 400 photos, 20 drawings, and 273 data pages composing a written narrative that is essentially a full-size book on the history and design of the bridge. Those interested in a detailed history of this bridge are encouraged to view their documentation.
The exact configuration of this massive bridge has changed over the years due to various projects, particularly on the approaches to the bridge. Thus, exact bridge lengths and span numbers vary depending on the source consulted.
The bridge is an extremely wide bridge capable of carrying large volumes of traffic, and indeed it carries an enormous amount, with an Average Daily Traffic of 270,000. One of the uncommon features of the bridge that allows it to carry this amount of traffic is that it is a double-deck bridge. The upper level carries westbound traffic, while the the lower level carries eastbound traffic.
California Department of Transportation (Caltrans), decided that the best way to deal with one of the most important historic bridges in the country was to demolish approximately half of the entire bridge (specifically the eastern bay spans) and replace them with mundane slabs of concrete held in place by a cable-stayed-like structure. This decision was made despite apparent alternatives that included rehabilitation and retrofit against seismic-related damage. The planned demolition of of half of the San Francisco Oakland Bay Bridge represents one of the greatest single losses of a historic resource in the modern history of the United States.
If the Western Spans and the Eastern Spans are considered two different bridges, their historic significance is nearly equal, each being an extremely significant bridge in its own right. However, together as a single bridge, they combine to form an even more significant bridge system. With the demolition of the eastern spans, the overall historic significance will be drastically reduced. The new bridge for the Eastern Spans will have no heritage value whatsoever, extremely limited (if any) aesthetic value, and it will bear no resemblance to the form and function of the historic spans. The Historic Significance Rating below reflects the significance of the bridge prior to the Eastern Spans demolition.
| Western Spans (Suspension Spans) Technical Facts |
| Rehabilitation Date | Main Span Length | Tower Length (From Water Level) | Structure Length | Main Spans |
| 2003 | 2,310 Feet (704.1 Meters) | 526 Feet (160 Meters) | 9,620 Feet (2,932.2 Meters) | 6 |
The Western Spans of the Bay Bridge are primarily composed of the six massive suspension spans of the Bay Bridge, stiffened by a riveted Warren truss system. Towers for the six suspension spans are composed of riveted steel, with an overall design that includes a massive lattice pattern of bracing between the tower posts.
From a historic and technological standpoint, the suspension spans are extremely unusual and technologically noteworthy because of their span configuration. Suspension bridges were generally designed for situations were the longest possible span over a massive feature was desired. As such, most suspension bridges have two towers that allow for a single massive central span between those two towers, just like the Golden Gate Bridge. However, the Western Spans contain four towers forming two central suspension spans and four arm suspension spans. In a sense, the bridge is like two traditionally composed suspension bridges lined up one right after the other. This configuration makes the Western Spans unique and distinctive, giving the bridge a strong sense of identity. The repeating, graceful curves of the suspension cables also give the bridge a high level of aesthetic value.
The Western Spans are the closest to busy San Francisco and they have traditionally been the most well-known and beloved by the general public due to the graceful appearance of the cables in the suspension bridge system as well as the impressive towers that hold those cables. The fact that they are closer to the metropolitan core city of San Francisco may have also added to their fame, since they are viewed by many tourists in the downtown area.
The Western Spans have been recently retrofitted and rehabilitated in conjunction with the project to demolish and replace the other half of the bridge. The retrofitting of the Western Spans of this bridge included the replacement of most of the v-lacing/lattice on the built-up beams composing the stiffening truss with perforated plate steel (the type commonly seen on 1950s and 1960s truss bridges). The HistoricBridges.org team has limited experience with the peculiarities of seismic retrofitting, but the question deserves to be asked if there might not have been another way to strengthen the stiffening truss beams without stripping the bridge of lattice and v-lacing, which are features that make the trusses more intricate and beautiful. In particular, it bears mentioning that the Golden Gate Bridge was retrofitted and rehabilitated without removing the extensive lattice and v-lacing present on its stiffening trusses.
| Eastern Spans (Cantilever Truss Spans) Technical Facts |
| Demolition Date (Expected) | Central Cantilever Span Length | Cantilever Anchor Arm Span Length | Eastern Spans Total Structure Length | Main Spans |
| 2013 | 1,400 Feet (426.7 Meters) | 580 Feet (176.7 Meters) | 10,176 Feet (3101.6 Meters) | 3 |
The Eastern Spans consist primarily of truss spans. The main feature is the enormous cantilever through truss structure which is an extremely important historic structure, and one of the most important examples of its type in the country. When it was built, it was the longest spanning and heaviest cantilever bridge in the United States. It remains among the longest spans ever built. Its overall composition is traditional in form, with two pointed towers, two anchor arm spans and a central span containing a suspended span. However there are some unique and distinctive details which the HAER documentation discusses.
There are also a series of through and deck truss spans on the Eastern Spans. The deck truss spans are Warren truss spans with riveted connections, while the through truss spans are modified (Baltimore style) Warren truss spans with riveted connections. The through truss spans are in fact individually historically significant on account of their length: each through truss span is 504 feet long, each containing 12 panels of 42 feet each. 504 feet is extremely long for a simple spanning, trapezoidal truss. Most through truss spans of this length, such as the 519 foot Brownsville Bridge (one of the largest truss spans in Pennsylvania) have a polygonal top chord, and as such are not trapezoidal trusses.
In the infamous 1989 Loma Prieta Earthquake, a single deck section failed on the Eastern Spans when some bolts sheared, causing the deck segment to crash down onto the lower deck, which in turn failed as well. While it was a tragic event that had fatalities, and it did point to a need to retrofit the bridge, the description of the event is often incorrectly described. Uninformed media and other individuals often wrongly describe this event as a partial bridge collapse. It was actually a deck collapse (and only a single deck span), the actual bridge superstructure remained intact, unlike the horrific collapse of the Cypress Street Viaduct in that same earthquake, in which both substructure and superstructure failure occurred.
The preference of the general public for the visual appearance of the suspension structure of the Western Spans is reflective of a general public who has failed to truly take a look at the Eastern Spans and appreciate the beauty contained within their design. The Eastern Spans may not have graceful curves or looming towers of a suspension bridge, yet they offer a different type of aesthetic which is an intricate geometric art which is formed from the complex arrangement of the trusses in the bridge, complimented by the lattice and v-lacing present on the built-up beams of the bridge.
The San Francisco Oakland Bay Bridge does not apparently enjoy the protection and perpetual existence that the nearby Golden Gate Bridge seems to enjoy. Caltrans is currently building a replacement bridge for the Eastern Spans on a slightly new alignment. Following the completion of this new bridge, the entirety of the historic Eastern Spans will be demolished, resulting in the complete destruction of one half of a bridge that is one of the largest and most important bridges in the United States.
Cantilever truss bridges are one of the most threatened historic bridge types in the country. Since they are usually used on long crossings that are expensive to bridge, and as such only a limited number of long-span bridges being built, cantilever bridges tend to be regionally important crossings that carry much traffic, resulting in functional obsolescence and structural deficiencies. This fact has lead to widespread demolition of a population of bridges that was never very large to begin with. This enhanced by the United States' transportation funding system that tends to reward agencies who propose costly replacement projects rather then rehabilitation projects that often are actually less expensive when properly designed.
Could the Eastern Spans have been retrofitted and rehabilitated? It certainly seems so. Other old historic bridges both large and small from the 4th Street Bridge to the Golden Gate Bridge have been rehabilitated and retrofitted in the seismically active San Francisco Bay area. In particular, the nearby Richmond-San Rafael Bridge, which is also a cantilever truss span similar to the Eastern Spans of the Bay Bridge was successfully retrofitted. Also, although the Eastern Spans superstructure type is different, it is worth noting that the Western Spans were rehabilitated and retrofitted, again raising concerns that rehabilitation of the Eastern Spans might also have been feasible.
This demolition of the Eastern Spans will occur despite the fact that with the exception of a few deck truss spans which have already been demolished, the historic spans are not in the way of their replacement. However, possibilities for preserving either part or all the historic Eastern Spans next to the replacement bridge were not given serious consideration any more than possibilities for simply rehabilitating and retrofitting the historic spans for continued vehicular use. Even with a decision to build a new spans on a different alignment, some or all of the historic bridge could have been preserved as part of an adaptive reuse. In January 2010, a group came out with a very different and unique adaptive reuse of the historic Eastern Spans. . HistoricBridges.org supports these proposals and it would be nice to see Caltrans support them as well, but at this time it does not appear that they do.
Earthquakes do present a unique challenge with historic bridge preservation, as do bridges like the Bay Bridge which are busy and are critically essential components of a regional infrastructure. However if the engineers of the 21st Century, equipped with centuries of knowledge, as well as computers and other technology, have even a fraction of the creativity and ingenuity of the inventors and engineers of the 19th Century, then HistoricBridges.org is confident that a preservation solution for the Eastern Spans that was safe and fiscally reasonable could have and should have been developed. The solution might not have been a cookie cutter design, it probably would have required designing and trying some new approaches. Instead, a preservation solution would have continued the spirit of bold thinking that resulted in historic bridges like the Golden Gate Bridge and Bay Bridge in the first place. Even relocating and preserving a single through truss span appears to have been beyond the scope of consideration. By choosing to demolish half of one of the largest, most complex, and historically significant manmade structures in the United States, Caltrans and all involved engineers and agencies have failed the American people.
The replacement bridge type is as a self-anchored suspension bridge. Because of the self-anchored design, Caltrans thinks the bridge is something revolutionary and state of the art. However, a self-anchored suspension bridge presents nothing new or remarkable to the engineering world. After all, Pittsburgh has three self-anchored suspension bridges, which dating to the 1920s, are historic bridges and far more beautiful in appearance and more significant to the engineering world.
The new bridge has been touted by Caltrans as a "signature" span that has a high level of aesthetic value. While it may be true that the arrangement of the cables has a somewhat appealing expression of a modern architectural form, the overall aesthetics of the design is ruined by the use of massive amounts of plain concrete to form a relatively mundane deck. This extensive use of concrete (which is typical of most modern bridges) makes much of the bridge look like little more than a ugly concrete freeway viaduct. In addition, the modern appearance of the bridge will not fit with the historical appearance and design of the surrounding bridge structures, including the Golden Gate Bridge, the Western Spans, and even the Richmond-San Rafael Bridge. As such, the bridge will look inappropriate and out of place. Finally, although the structure type of the new bridge is a suspension bridge, the single tower configuration coupled with a main cable that slopes down at a sharp angle to a massive concrete deck, in truth makes the bridge look like little more than a modern cable-stayed bridge. Cable-stayed bridges are rapidly becoming the most common structure type in the country for long-span bridges, as the wide variety of large span historic bridge types in the country are being demolished and replaced with these modern bridges. As such, the new Eastern Spans bridge will have a general appearance that will be vastly similar to the countless mundane cable-stayed bridges that are covering the face of this country.
It is worth noting that for a variety of reasons, the new bridge has been controversial, particularly during the period in which alternatives and design types were being considered. There was even an entire website created by concerned individuals. Issues includes rising costs of building the bridge, as well as concerns about the seismic safety of the bridge. The new bridge design has since been certified to be seismically safe, yet at the same time it is questionable how much more protection the bridge actually offers versus a well-planned rehabilitation and retrofit of the historic spans, especially when considering other retrofitted historic bridges such as the Golden Gate Bridge.
Since the HistoricBridges.org team has not yet been able to visit and photo-document this historic bridge in person, this bridge's photo gallery is composed of Public Photograph Compilations (PPCs), which are composed from select photos from public repositories like Flickr, and organized and combined into the familiar HistoricBridges.org photo gallery format. The photos are legally offered by HistoricBridges.org under the terms of a Creative Commons license. As required under the license, HistoricBridges.org hereby states that none of the photographers endorse HistoricBridges.org and its ideas, nor are they affiliated with HistoricBridges.org in any way. Learn more about HistoricBridges.org's Public Photograph Compilations here. Also please note that most photos in this Public Photograph Compilations are overview photos and the usual comprehensive set of detail photos associated with a HistoricBridges.org photo-documentation will not be present.
