The Commissioning, Design, and Public Perception of Urban Bridges
Anthony C. Webster
Director of Building Technologies / Assistant Professor of Architecture
Columbia University - Graduate School of Architecture
As published in the Journal of Urban Technology
This paper examines the purposes, ownership, commissioning, design and public perception of Post WW II urban bridges in the U.S.
More often than not, America views its bridge infrastructure as a set of utilitarian artifacts, erected primarily for transport. Unlike Europe, were competitions for prominent urban bridges are common, and their funding comes from a variety of cultural and technical organizations, America's important urban crossings are usually designed by the same processes that are used for exurban overpasses, and their funding is provided by agencies charged solely with making transportation more efficient. The importance of the tiny fraction of American urban bridges that speak to larger civic needs is underscored by their anomalous commissioning, funding and design methods, as well as by their prominence. The current poor condition of Americas bridges -- the U.S. General Accounting Office reported in 1991 that about 40% of the nations bridges are deficient (Bridge Infrastructure 1991) -- ensures that a large number of urban bridges will require replacement during the next 20 years. This in turn gives Americans a unique opportunity to decide wether our cities shall continue to be spanned by vehicle-carrying conduits or modulated by multipurpose civic crossings.
Normative U.S. Bridge Creation Processes and Players
State or county governments own most major U.S. bridges, and technically
oriented state agencies usually administer them. In New York, for example, the
State owns 16 of the 20 major bridges over the Hudson River, and the New York
State Department of Transportation (NYSDOT), which is staffed largely by
engineers, maintains them (Bridges 1984). The George Washington Bridge is
owned by the Port Authority of NY and NJ, which has approximately 1,000
engineers on its staff.
The remaining three major structures are owned and administered by railroad interests for trains. In California, the situation is similar - - the state government owns all the auto-bearing bridges along its state and federal highways. Caltrans, a state bureaucracy comprised mainly of engineers, is responsible for the maintenance of these structures.
Major urban bridges are almost always paid for by state funds or by a combination of state and federal funds that have been earmarked specifically for highway construction or improvement. Federal funds are available primarily from the Federal Highway Administration (FHWA), under the "Surface Transportation Assistance Act of 1978" (Bridge 1991). Both federal and state monies come from gasoline or vehicle tax revenues. On the federal level, this income goes into the highway trust fund, which the FHWA administers. The 1991 "Intermodal Surface Transportation Efficiency Act (ISTEA) " also allocates some Federal moneys for bridges and related amenities, but its budget is dwarfed by the highway trust fund, and its future is not assured (ISTEA 1995).
State transportation bureaucracies generally commission new bridges, which are designed by either engineers within the bureaucracies themselves or by consulting engineering firms working closely with them. In New York, the NYSDOT determines when a particular bridge will be commissioned, and solicits design proposals from engineering consultants by advertising in civil engineering trade publications. Consultant selection is based on reputation, technical approach, workload, and projected design fees. The chosen consulting engineer's construction documents are let for public bid and the lowest bidding contractor is retained to build the structure. In California, Caltrans decides what needs building and uses its in-house staff to design it. The resulting construction documents are then let and, as in New York, the low bid contractor generally builds the bridge. Under both systems, competitions for design proposals are almost unheard of.
These representative processes of bridge creation have at least two serious
flaws. First, the entire procurement process is controlled by technically
trained bureaucrats whose concerns extend only slightly beyond utility and
Structures these engineers produce are of course "designed" in the technical sense that they are scaled to accommodate the traffic flowing over them, and that their components are strong enough to carry this traffic safely. But "design" issues as understood by architects and urban designers -- including siting, formal expression, and the experience of being on or traveling across them -- are typically not addressed. The FHWA and state DOT's obsession with producing the most economically efficient conduit possible has encouraged bridge builders to treat their products as commodities. Not unlike the 19th century pattern books of Asher Benjamin and others (Benjamin 1827), which led to the pervasive use of certain architectural features,
the FHWA has published a number of standard bridge designs, in the hope that state DOT's will routinely adopt them (Standard 1984). In contrast to Benjamin's goals, the FHWA publications are not concerned with promulgating a particular style -- they are instead aimed at "reduc[ing] costs by reducing the time needed to design bridges" (Limited 1984). The FHWA's structures can easily be modified to accommodate one to four spans and a total length of up to 480 feet (figure ). To accommodate variations in local construction expertise and material costs, the FHWA has published cast in place, precast, and composite models. As a drive almost anywhere in America demonstrates, the FHWA's designs are in fact frequently used by state DOT's.
The result of these normative bridge building practices is that, as Architectural Record's editors have recently pointed out, "today, it is rare to find a bridge that departs even slightly from the ultra-standardized civil engineering kit of parts." (Russell, 1993). It should be expected that engineering professionals, whose design education does not include any consideration of siting, aesthetics, or spatial experience, will produce cost efficient structures in response to the pressures of a cost conscience public. It is less expected, but also unfortunately true, that architectural and urban design issues are not considered in the procurement of almost any contemporary American bridges. Because there are so few alternate methods for commissioning bridges, this is nonetheless the case.
For urban areas in particular, a more important problem of America's contemporary bridge procurement system is that auto interests fund it almost exclusively. As its name implies, the Federal Highway Administration's mission is to administer bridges as pieces of autoroutes. The gasoline-based tax revenues that pay for America's bridges further skew the bridge building community toward the auto conduit. Given the hegemony of the automobile as a transportation medium in America, a technically oriented, lowest cost approach is arguably appropriate for creating many rural and suburban bridges. Considering bridges as simply utilitarian armatures for auto travel is less appropriate for cities, whose needs include pedestrian circulation, maintaining and expanding their public realms, and the expression of their civic personas.
Art Applied to Artifacts / Forms from Pre-existing Types
Some cities and states have attempted to enlarge the circle of issues included in bridge design, primarily by improving aesthetics. The city of Phoenix, for example, has decided that "the public is demanding more than utility and economy" (Cannon 1992), and has responded with a requirement that 1% of its capital construction budget for civil engineering projects go toward "the inclusion of art" in them. As part of this program, an artist designed adobe and concrete reliefs for the city's recently completed Squaw Peak Parkway Interchange. The artist built the reliefs into retaining walls and columns, and modified the profiles of the columns to allude to local native American figures (figure ). Although the bridge's designers were aware that the interchange would "disrupt neighborhoods with concrete, traffic and noise," these issues were not treated as design problems, but were instead accepted as an inevitable byproduct of the highway's expansion. In fact, the plan and sectional details of the bridge are very similar to the FHWA's standard designs, much as they would be adopted for use as a rural overpass. The artist's contribution to the Squaw Peak project was limited to installing a visual applique over a pre-engineered artifact.
The idea of awarding an architect or artist the limited brief of refining the formal expression of pre-conceived bridges is of course not new. As O. H. Ammann, the master engineer and chief designer of the George Washington Bridge reported in 1933, Cass Gilbert was retained by the Port of New York Authority to, among other things, "materially enhance the [bridge's towers] by an encasement with an architectural treatment" (Ammann 1933) (figure ). Fortunately, the towers were left unclad, and many keen eyed observers have since praised the bridge. Le Corbusier, for example, wrote "The George Washington Bridge over the Hudson is the most beautiful bridge in the world...between water and sky, you see nothing but bent cord supported by two steel towers. When your car moves up the ramp the two towers rise so high that it brings you happiness; their structure is so pure, so resolute, so regular that here, finally, steel architecture seems to laugh" (Le Corbusier 1947).
In a more ambitious program than Phoenix's, Caltrans created a "Bridge Architectural Section" in 1962, which currently consists of eleven architects and illustrators, and participates in the design of all of Caltran's bridges (Roberts 1992). The design process for a typical bridge begins with a "bridge design team" -- which includes an architect -- developing a few schematic proposals. A "type selection committee," including a structural engineer, construction engineer, maintenance engineer, and architect reviews the proposals, and decides which one to execute, based on an analysis of technical viability, construction costs, and aesthetic considerations. In describing the program, Caltrans notes that prior to 1962, economics was the major determinant of its bridge designs, and that the costs of including aesthetic considerations under the current system are negligible.
Like the Phoenix program, the result of Caltrans' design process is to put an aesthetically pleasing patina over a structural commodity. This is underscored by the fact that 90% of California's state highway bridges are designed as concrete, cast in place box girders. In the special instances where Caltrans has deviated from box girders, it has usually produced copies of well- known structures pioneered by twentieth century masters (figures , , , ). As with the FHWAs bridge designs, Caltrans special bridges are based on a small number of types -- the types in Caltrans case are derived from outstanding examples of the engineers craft.
Technical and Aesthetic Elegance in Long Span Bridges
Although rare, some handsomely proportioned and sometimes stunning bridges have been recently erected in the U.S. Florida's Sunshine Skyway and Dame Point bridges were among the first major cable stayed bridges in the U.S. (figure ) (Morse, 1988). Their attenuated ephemeral expression, like many of their European precursors, is unique among longspan bridges. The New River Gorge Bridge in West Virginia, when completed in 1977 become both the world's lengthiest steel arch span (figure ), and a graceful addition to the long-span ferrous arch bridge tradition that can be traced to Eiffel and earlier (figure ).
The existence and beauty of these bridges is traceable to their utilitarian purpose and their length, respectively. As rural or exurban structures serving as links along major state or interstate highways, the bridges were located for vehicular convenience and financed by Federal and local highway trust funds. Their silhouettes -- designed by civil engineers -- were determined by the economy of their structural systems (arches or cable stays) in spanning long distances, as well as by the idiosyncrasies of the local construction markets (figure ). The bridges' particular designs were in fact largely justified by their low cost in comparison to other structural alternatives (Johnson 1992). The congruence between these bridges' visual elegance and their structural economy is an accident of their size (figure ); if their spans had been shorter, the material and constructive economies of their particular forms would not have held true, and they would almost certainly have been developed in accord with FHWA standard designs.
Special Needs of Urban Bridges and Some Special Approaches to Their Design
For many urban bridges to realize their full civic potential, siting, programmatic content, and pedestrian access are as important as aesthetics, utility and economic efficiency. Unfortunately, there are no happy accidents of physics that ensure that urban design issues are addressed in urban bridges of any length. The complex nature of these structures makes it much more difficult to find designers or design teams with the breadth of talent required to envision them, and almost impossible to find the funds to realize them. Indeed, transportation improvements in general and bridge-like structures in particular are as well known for their degradation of urban life as for their improvements in transportation efficiency. The situation in Boston's Charlestown district at the turn of the century illustrates the problems that elevated armatures for trains have introduced into urban environments. J. Anthony Lucas has captured the deleterious effects of that community's first train line (Lucas, 1985):
Then, in 1901 came the elevated railway, which not only quadrupled the traffic passing through Charlestown but put much of it in shadow and split it into fragments on either side of the tracks. From the West End, the El screeched across the bridge to Charlestown's City Square, then up main street toward the suburbs. For long-range commuters, it was a blessing,...for Charlestown it was a curse, a hissing monster which brought noise, dirt and darkness to the town...Within ten years of its completion, the El had become an emblem of exploitation.
Fortunately, some contemporary American bridges have been designed to address the needs of urban placemaking and improving the fabric of city life. The very small number of these structures currently being designed or recently completed is statistically insignificant compared to the 75,000 American bridges that stand to be replaced or reconstructed in the next ten years. Nonetheless, because they have been widely reported, and because of their prominence as civic icons, they are among America's most important contemporary bridges, and are useful in suggesting new processes for the development of urban infrastructure.
The city of Minneapolis, for example, used the creation of its 1988 Whitney Pedestrian Bridge to repair the rent in its city fabric created by interstate I-94, while also creating a new public place (figure [16 General View.]) (Lassar 1990). The bridge, designed spatially and formally by artist Siah Armajani, spans over 16 lanes of freeway to connect the Walker Art Gallery's sculpture garden with a city park. In addition to being used as a transportation link by workers and museum-goers, the structure has become a public attraction in its own right, drawing "numerous joggers, cyclists, lovers and tourists [to it]" (Tomkins 1990). Benches and the bridge's periodic outward bowing in plan invite lingering, making it a place to be as well as structure for transportation.
The bridge's funding, commissioning, and design processes are as unusual as its overlapping structural systems are ambiguous. The Wheelock Whitney family and the Minnesota Department of Transportation, which now owns the bridge, equally split its 1.6 million dollar cost. Armajani received the commission to design it -- in both formal and structural terms -- after he won an invited competition for its schematic design. Armajani hired his own engineering consultants help him work out technical details.
A project that addresses civic needs while expanding an existing autoroute is the projected replacement structure for the Wabasha Street Bridge across the Mississippi River in nearby St. Paul. James Carpenter, who trained as an architect at the Rhode Island School of Design before taking a degree in sculpture, has developed three alternate schemes for the replacement of the existing, 150 year old structure (Carpenter 1993). Of the schemes, which collectively won a 1993 PA design award (Wabasha 1994), Carpenter's twin mast cable stayed solution is the most visually interesting (figure ); its canted towers and stays would rise high enough above the river and most of the city's monotonous skyline to create a new urban landmark. This design would also separate motorized traffic from pedestrians and bicycles by lifting the latter above the roadway for most of the bridge's length - improving both the air quality and noise level for them. Although the projected 55 million dollar cost of the cable stayed scheme will prevent its being erected, construction of the 32 million dollar concrete haunched girder alternate (figure ) is scheduled to begin in 1996. Fortunately, this design includes the key urban amenities of the cable stayed proposal. The new bridge will replace three traffic lanes and crowded pedestrian & bike ways with four lanes of auto traffic, as well as wider pedestrian and bicycle paths. It will also provide a pedestrian connection to a currently inaccessible island in the middle of the waterway, which is expected to feature riverside promenades and playing fields for various sports.
Like the Whitney Pedestrian Bridge, the funding, commissioning, and design processes for the Wabasha Street bridge are extremely unusual. Carpenter was commissioned to prepare a preliminary design the bridge by the City of St. Paul's Department of Public works after a 14 member advisory panel chose him from among 60 prospective designers. Carpenter retained the German engineer Joerg Schlaich to help develop the structure's technical details of the cable stayed scheme -- including its structural system and the materials and forms of its connections -- while generating the bridge's circulation system and overall silhouette himself. The Carpenter -- Schlaich collaboration stands in stark contrast to commissions like the George Washington Bridge, where an architect (Cass Gilbert) is retained to lay a skin over a pre-designed structure.
While a local civic group tried unsuccessfully to raise the funds for the cable stayed structure, Carpenter developed one of the concrete haunched girder design with Figg Engineering. The $32 million dollar projected expense of this scheme proved close enough to normative auto bridge costs that it will be funded almost exclusively by federal and state highway trust funds. By choosing to build the haunched girder proposal, St Paul has lost the opportunity to create a unique landmark and to enhance the experience of crossing the bridge for cyclists and pedestrians. The city will, however, benefit from the improved pedestrian movement and bicycle flow across the river, as well as by gaining public access to its island park.
St. Paul's Wabasha Street Bridge replacement is complimenting the city's effort to reinvigorate the adjacent derelict waterfront area. With encouragement from the city, the Minnesota Science Museum has recently commissioned the design a new facility at water's edge nearby; the National Park Service is planning to locate a Mississippi River Interpretive Center nearby, as part of its establishment of the country's first urban national park along both sides of the river (Carpenter 1994).
Urban bridges that serve a variety of civic purposes are less rare in Europe. The efforts of bridge designers such as Santiago Calatrava and Marc Mimram are testimony to the European desire for bridges that enhance civic spaces. Calatrava, a Valencian architect/engineer, has to-date designed seven mixed use urban bridges that consistently address problems of formal and structural expression, location and casual access. His 1987 Bach de Roda Bridge in Barcelona possibly best exemplifies his synthetic approach (figure ). Calatrava's twin arch structure was commissioned by the city to link two districts separated by a 40 meter wide rail cutting, and to provide access to a new adjacent park. The primary arches are braced against buckling by secondary, canted arches of equal height. Angled suspenders, lying in the plane of the secondary arches, brace the main arches against buckling, and help support a pedestrian walkway at the roadway level (figure ). The walkway's edge is bowed outward in plan, reflecting the arch's elevation while creating a pedestrian plaza at the center of the bridge. The sloped suspender ropes at the walkway's edge and the main roadway suspenders themselves define the limits of the plaza in three dimensions. The concrete abutments of the secondary arches are flanked by concrete stairways, descending from the pedestrian platform to the new park below (figure ). With the introduction of the pedestrian plazas and circulation system, Calatrava transforms, as Kenneth Frampton notes "the mere commission for a bridge into an occasion for creating a place" (Blaser, 1990).
Unlike the methods used to fund America's urban bridges, the Bach de Roda bridge was paid for by the city of Barcelona from a civic improvement fund largely independent of highway monies (IMPU 1992). This funding system certainly encouraged the resolution of the Bach de Roda bridge as more than simply a utilitarian armature. Staging competitions is another technique often used in Europe to foster bridge designs that speak to a variety of urban needs. Eight of Calatrava's thirty three extant bridge designs (including projects, urban and exurban commissions) were initially European competition entries. Marc Mimram's winning design for the Solferino footbridge over the Seine in Paris illustrates many features of French competition-commissioned bridge design (figure ). In 1992, the Louvre Museum announced a competition for a new pedestrian bridge connecting the Louvre and the Musée d'Orsay, and asked for submissions from interested architect-engineer teams (Mimram 1994). The Louvre asked eleven of the approximately 100 respondents to develop preliminary design proposal. Mimram, who like Calatrava is trained as both an architect and an engineer, was then awarded the commission for the bridge. France's Ministry of Culture and the Ministry of Equipment and Transportation (which pays for most of Frances bridges) are jointly funding the structure, which is scheduled to be completed in 1996. Although not always used for such high-profile commissions, between six and ten such competition- commissioned bridges are designed in France on average each year.
Competitions for bridges in the U.S., by contrast, are extremely rare. One of the few recent American bridge competitions was mounted in 1987 by a technical advisory panel chartered by New York City to explore the possible replacement of the Williamsburg Bridge (Williamsburg 1988). One of the most interesting results of the project was that, although the advisory panel designed the competition as a technical exercise -- advertising internationally in various engineering journals and soliciting entries from pre-eminent engineering firms -- a number of entries were submitted by engineer/architecture teams (figure ). Entries by Ove Arup (engineers) & Michael Fieldman/Harry Wolf (architects), Bruno Thurliman & I. M. Pei, Jenny Engineering & Ehrenkrantz and Eckstut, DRC Consultants & Der Scutt, and Skidmore Owings and Merrill (architects and engineers), posited a variety of amenities for the proposed bridge, including new parks and public spaces, bicycle and pedestrian paths, and observation decks (Williamsburg Bridge 1988). These collaborative efforts show that architects and engineers are interested and able to work together on America's urban infrastructure needs if given the opportunity to do so.
Choices and Opportunities for the Future
There is some reason to believe that in the coming years, the commissioning and funding mechanisms for American urban bridges that address placemaking and civic expression may become less extraordinary. One reason is the "Intermodal Surface Transportation Efficiency Act (ISTEA)," authored by Patrick Moynahan and signed into law in 1991 (Plungis 1992). The bill, which allocates spending of approximately $155 billion over the next six years, funds the development and redevelopment of transportation systems, and helps underwrite the cost of creating new technologies, such as mag-lev trains and intelligent vehicle highways (Summary 1992). Equally important, the bill includes a modest amount of funding for civic amenities, including the creation of public places associated with transportation nodes, and the redevelopment of historic public-works-related structures. Perhaps most important, as its name almost suggests, the legislation recognizes the need for a multimodal approach, in its funding for bike paths and walkways, as well as auto routes. This approach puts the legislation in sharp contrast with the FHWA inspired funding process, which, being based on auto revenues, has proven unable to move past the idea that bridges are simply vehicular conduits.
Already, some municipalities are planning to exploit ISTEA's recognition of public places and multimodal transportation to improve their public realm. Los Angeles, for example, is hoping to use ISTEA funding to help establish a series of greenways adjacent to some of its proposed new roads (Russell 1993).
Another reason to suspect that America's approach to bridge-building may be shifting, is the recent advocacy of a richer urban infrastructure by design professionals. ISTEA's most progressive aspects were incorporated largely due to the efforts of the Surface Transportation Policy Project (STPP), comprised of the AIA, ASLA, urban planners, and National Trust for Historic Preservation. This type of legislative lobbying is new to much of the design community. As Lisa Wormser of STPP points out, "this was the first time we went beyond handcuffing ourselves in the path of bulldozers" (Russell 1993).
The AIA's Pittsburgh chapter has recently also played a proactive role in improving projected bridge proposals in that city (figure ) (Russell 1993). After local authorities proposed a stodgy replacement for the city's Wabash Bridge, the local AIA chapter sponsored a charrette to design an alternate scheme, which has since been embraced by local planners, public agencies and the local press.
These efforts take on a special poignancy in the face of the deteriorated state of America's bridges. Approximately 40% of the nations 578,000 bridges are currently considered deficient by the U.S. General Accounting Office (Bridge Infrastructure 1991), and it will cost $51 billion to refurbish them. About 150 of these bridges become too unsafe to use or fail structurally each year (Wasley 1992). As alarming as these statistics are, they also make this a particularly opportune time for American cities to re-think the contributions that their urban bridges can make to their civic life and heritage. At the same time, efforts such as James Carpenter's, STTP's, the AIA's Pittsburgh chapter, and the interdisciplinary response to the Williamsburg Bridge competition show that portions of America's design community are interested in working together to improve our urban infrastructure's contribution to the public realm. If more projects like these take hold and funding mechanisms for them (including both private sector and ISTEA sources), the potential of bridges to positively contribute to the fabric of our cities will increasingly, and happily, become a reality.
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Culturally Innovative Approaches to Urban Bridge Design