space laboratory for architectural
research and design
Professor Steffen Lehmann
Chair in Architecture, Brisbane / Newcastle
Abstract
The design of infrastructure such as motorways, tunnels and bridges is an important design task for our built environment. Today, many Australian cities such as Sydney and Brisbane have experienced rapid growth and are under pressure to provide good transport and connectivity systems. The paths and networks of movement are the most potent means by which an urban complex can be ordered. Foot and cycle bridges are a powerful means of improving the connectivity between the separated banks of a waterway. However, is a bridge a building, a landmark, a room, a road, an urban promenade, an observation deck, a gateway, roof, stage or monument? At the very least, footbridges improve the "walkability" of a place. But consider the energy and silhouette that an elegant, slender footbridge could create; and think of the different experience of being on a bridge compared to using a tunnel. The quality of design of such infrastructures sends a strong signal about civic pride to citizens, visitors and potential investors. This paper reflects on the collaboration between engineers and architects, illustrates some recent examples of the exciting design for new footbridges, and reports on the outcome of a study suggesting five new footbridges for Brisbane.
Keywords
The engineer-architect relationship; collaborative process; investments in infrastructure and public space; reducing car dependence; structural principles; landmark potential
Introduction
The author's research grew out of his desire to better understand the potential of infrastructure and public space, how public spaces are linked to infrastructure elements, and how the network of such places defines the circulation patterns in a city. There is an urgent need for good public space, for waterfront parks, for effective linkages and improved infrastructure in any urban environment. With a steadily increasing urbanised population Australian cities require useable public domains and improved public transport systems. Public space should be central to the planning for growing cities, thus making urban design an outcome, rather than a discipline.
Today, we acknowledge that infrastructures such as motorways, tunnels and bridges are an important design task for our built environment. Cities such as Sydney and Brisbane are under pressure to provide better transportation and connectivity to a growing population. It is therefore reasonable to assume that if we are to invest significant public money in new urban infrastructure, then we must ensure that quality design outcomes are achieved, without exception. The quality of design of such infrastructure sends strong signals to the local community and to capital investors alike.
The paths and the network of movement are the most potent means by which an urban complex can be ordered. Foot and cycle bridges are a powerful means of improving the connectivity between the separated banks of a waterway.
An urban promenade and gateway: movement through the city
Most of the time, we experience the city while moving through it. Circulation, movement and linkage are the keys to how we use a city. In that case, let's deliberately design these paths and improve movement through the city. For Brisbane, a series of foot and cycle bridges would open-up new possibilities for pedestrians to move through the city, and be positive connecting elements to currently inaccessible locales. But first, perhaps, we need to know how to define what a bridge actually is? Is it a building, a landmark, a room, a road, an urban promenade, an observation deck, a gateway, roof, stage, monument? What is it? What are its possibilities? What is its role?
At the very least, a footbridge is a connecting element. It has the potential to create new urban energy as, for example, the elegant new bridges in Barcelona, Paris and London. These bridges have improved the 'walkability' of a place. And consider the artistic silhouette that such an elegant, slender footbridge can create; and think of the different experience of being on a bridge, mid-river, compared to using, for instance, a tunnel.
Future scenario: improvement of the connectivity, linking up places
Brisbane is a river city. It is under pressure from its rapid urban growth. It is experiencing increased demands on its transport system and the ability of the inhabitants to connect efficiently to other parts of the city. The skyline of the central business district as it looms up from river bends, along with the magnificent Botanical Gardens and the few existing bridge crossings characterise the city centre. However, the connectivity between the two sides of the river is, for its size, surprisingly poor. As a result, people frequently need to travel long distances to get from one side to the other. Thus the car has become a well-loved necessity for the residents. This scenario presents us with a challenge: how can pedestrians reclaim the city and its public spaces?
The educational context: 3 conceptual models of collaboration
In times of rapid change, we become increasingly aware of the need to look beyond conventional discipline boundaries and to develop more appropriate cross-discipline studio models for architecture and engineering students. To explore the idea of 'bringing together' different disciplines like engineers and architects, it is important to examine in detail the differences between three collaborative studio models which the author coordinated in the previous academic year. Each pedagogical model represented ways in which different disciplines could be drawn together, by creating alternative learning situations in design education. These collaborative studios differ from the traditional design studios in that they are focussed on cross-disciplinary creativity. The advantage of such collaborative studios is that they produce students who are highly motivated, who produce rigour and depth in their work, and have a broader knowledge bases. The three models with varying levels of cross-collaboration consisted of:
Studio model 1: Students working side-by-side on the same project, each producing their own proposal ('Transdisciplinary encounter model', Fig. 1).
Studio model 2: Students working in multidisciplinary teams, each encompassing architecture and visual arts students collaborating on joint individual projects ('real team collaboration model', Fig. 2).
Studio model 3: Architecture students inviting students from engineering to come to the studio, from time to time, as external consulting experts on, for instance, traffic planning ('interdisciplinary consultation model', Fig. 3). This model is closest to the standards of 'real' architectural practice and was the model used for the project 'Brisbane Bridges'.
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 Fig. 1: Diagram of model 1: 'Transdisciplinary encounter model'. |
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| Fig. 2: Diagram of model 2: 'Real team collaboration model'. |
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| Fig. 3: Diagram of model 3: 'Interdisciplinary consultation model'. |
The architect-engineer relationship
Today we recognise that the design of infrastructure such as motorways, tunnels and bridges is an important and complex design task with a strong impact on our built environment. This complexity encourages collaborative design processes where engineers and architects are equally involved. In the past, bridges were considered to be part of the engineer's realm rather than the architect's. However, the architecture of infrastructure can be very powerful in terms of its sculptural possibilities. In the 19th century, the history of engineering — for instance the construction of cathedrals and bridges — was often a chronicle of risk-taking, with construction on an extraordinary scale. Increasingly, during the last twenty years, the relationship between innovative architects and their structural engineers has become more collaborative. No longer does the architect simply hand over concept drawings for stability calculations. This has applied especially to bridge design since the introduction of non-regular geometries (eg. cable net or suspension structures), which require a very high level of coordination and collaboration between disciplines. Some good examples of this are the Spanish engineer-architect Santiago Calatrava and the German engineer Joerg Schlaich: both have built, in the last few decades, a series of innovative bridges in Barcelona, Bilbao, Stuttgart and Berlin, which only became possible in the computer-era and which effectively re-wrote the lexicon of bridge construction.
The future for engineers and architects is to work together towards an interdisciplinary future, where each capitalises on the potential of the other and exposes themselves to new design knowledge through collaborative practice and multidisciplinary teams.
Great cities have great bridges
Cities in the past used to have walls, not only for defence but to separate the urban from the non-urban realm. Entry to the city was through a gate left open during daylight hours and closed at night. Like all thresholds, the gate became an important focus for activities other than acts of arrival or departure. Although the Industrial Revolution changed the form of cities, the idea of the city gate still remained until in the 19th century, when it was replaced by the bridge and the railway station. For centuries, the need to provide passage over natural obstacles like rivers, to connect one side with the other in order to provide continuity to a route, has inspired different ideas for bridges. The most beautiful cities on rivers are often identified by footbridges that have become iconic landmarks — just think of the Ponte Vecchio in Florence, the Charles Bridge in Prague, or, more recently, the Millennium Bridge in London.
Historical precedents: Medieval bridges in Venice, Florence and Paris
The European medieval city and its relationship to the bridge is an interesting starting point for a short historical survey of footbridges, especially the typology of the 'inhabited bridge'. However, the most common model at the time was the arch bridge built of stone, where the span is limited by technical ability.
Some of the most well-known bridge structures include the Rialto Bridge in Venice, the Ponte Vecchio in Florence, and Pont Notre-Dame in Paris.
The Rialto Bridge is a classic. It crosses the Canal Grande and is a good example of 'town planning meets commercial interests', where the bridge is lined on both sides with shops. The painting 'Regata a Rialto' (1494) by Vittore Carpaccio shows the bridge as a timber construction. The Rialto has crossed the canal at this point since 1250. Around 1580 it became necessary to build a larger bridge in stone due to intensive traffic. Designed by architect Antonio dal Ponte as one single arch, the bridge was completed in 1591. The proposal of his competitor Vincenzo Scamozzi consisted of three arches, but obviously this design did not meet with the approval of the Venice Senate. Another painting, by Francesco Guardi (1740), entitled 'Il Ponte di Rialto' shows the bridge as it was 150 years later.
'Ponte Vecchio', the 'old bridge', crossing the River Arno in Florence, dates back to 1345. Again, the bridge is clearly a gateway to the city, and is only traversed after a toll has been paid. It is an urban element of primary importance to the entire city structure. Construction was initiated by the Grand Duke de Medici, and soon became much more than just a means of crossing the river, rather becoming a primary structure of the city. A painting by Bernardo Bellotto (1742) illustrates this well. Ponte Vecchio was built with two piers and three arches, in stone, replacing an earlier wooden structure, and integrating shops and apartments. It was destroyed by flood and fire several times, but it was always rebuilt. It is reported that in the 14 th century there were 47 shops on the bridge.
A painting by Nicolas Raguenet (1756) shows the inhabited 'Pont Notre-Dame' in Paris. The bridge's construction dates back to 1414. However, the bridge was constantly altered and extended during the centuries. This fortified stone bridge crossing the River Seine does not exist today, as it was destroyed during the French revolution.
We can find early model for the 'covered bridge' also: The Bassano Bridge, close to Lucerne in Switzerland, for instance, is an example of a bridge with a roof. This type of bridge is mostly found in mountainous areas, to protect the timber from snow and ice and to keep the path free of blockages. The bridge was designed by architect Andrea Palladio in 1561, illustrated in a 19 th century engraving: the interior view of this sixty metres long, wooden bridge shows how wide and generous the bridge was and how it offered a meeting place for two communities.
Bridge structures can also be found in the mega structures of 20 th century New York and Tokyo. Raimund Hood's collage (1925) entitled Manhattan in the year 1950 visualises his idea for the future development of New York where up to twenty new bridges connect the peninsula on all sides to form a 'bridge city'. Some 50,000 people were supposed to live on this bridge. Kenzo Tange's plan for Tokyo Bay, a montage of an aerial photo from 1960, followed a similar idea: an inhabited bridge structure to reclaim land from the sea and to service the rapid population growth of Tokyo. This linear, multilevel structure crossed the entire Bay of Tokyo, which is approximately ten kilometres wide.
Another typology is the 'bridge building crossing the motorway', an idea that originated in the 1950s in Italy. Here, the cafeteria is above the road, and there is a motel for the driver. See: 1965: 'Pavesi' motel by Antonio Bianchetti. 1967: a restaurant crossing the Northern Illinois Toll Highway, by David Haid.
Landmarks
The tourism value of such well-designed bridges should not be underestimated. What would be Venice without its many characteristic bridges, for example?
People are and have always been attracted to well-designed pieces of engineering, old and new, large-scale and small-scale.
Quality city infrastructure and public space
Quality design of infrastructure is a strong statement about civic pride. It signals a city's ambition to its citizens, visitors, would-be residents and potential investors. In other words, the procurement of quality city infrastructure — from bridges to sewage pumping works to council buildings — is paramount. A city says a lot about itself by the way it designs the most obvious pieces of engineering, such as its 'skeleton' of streets, its pedestrian and cycle paths and the associated elements of rails, fencing, culverts, retaining walls, balustrades, etc. Poorly designed and poorly maintained, these pieces reflect the self-image of the city. It is imperative, therefore, that an ambitious city utilises a design-led approach to improving the quality of its infrastructure.
So, what should be the characteristics of such new pedestrian and cycle bridges? Are there any examples from European cities that could be used for inspiration?
Let's look briefly at a kaleidoscope of new bridges: Recent examples from Santiago Calatrava (Spain), Marc Mimram (France), Arup Engineers (UK/worldwide), and Joerg Schlaich (Germany).
Transparent structures - a technical challenge
During the development of the design proposals for the pedestrian bridges, some specific constraints and concerns needed to be recognised and a series of crucial questions needed to be answered: What are the symbolic and political functions of such new linkages for a city like Brisbane? How can it be ensured that a light, transparent structure for the bridge sufficiently minimises the visual impact on the river scenery? What is the appropriate level of expressive engineering structure for such a bridge, and how could we span the river in the most elegant manner? In other words: can we transfer a technical problem into a poetic solution?
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| Fig. 4: Visualisation of Brisbane's CBD in 2020, with improved connectivity (from: CBD Draft Masterplan, 2005) |
Brisbane: A master plan for 5 new pedestrian bridges to improve the connectivity
Some of the technical constraints for pedestrian bridges are, of course, immense, for instance the requirement of minimum clearance for ship navigation beneath the bridge deck or the need for a high efficiency steel structure, since the Brisbane River in some areas is around 350 metres wide. There are various structural typologies available, ranging from suspension bridges to cable-stayed bridges, arch bridges to box girder bridges. Given the objective to minimise the impact on the scenery and to respect the sometimes differing topography on either side of the river, our research found that a light and transparent structure, reminiscent of a cable-stayed or suspension bridge, would be most likely to give the required results. Most important of all, the study identified a large potential response to the identified needs. For example, some of the proposed designs had the pedestrian walkway separated from the bicycle lane, others offered a protective wind-screen or roof cover for shading, so that users would feel more sheltered when crossing. Other designs suggested an observation deck with a café, half way over the bridge, from which customers would be able to appreciate the city from a new vantage point. The bridge's silhouette, characterised by slender pylons, provided an enhancement to the evening cityscape.
The need to design efficient structures to reduce the amount of steel is obvious. The design needed to recognise a way in which to build the structure; eg. prefabrication methods and size of modular elements.
Some of the difficulties engineers and architects face in designing bridges are:
The design also needs to be flexible enough to accommodate changes? Remember the increasing movement in the Millennium Bridge in London, where afterwards dumpers had to be installed. Then there are the aesthetic challenges, beyond the pragmatics of structural and material constraints. How do you articulate and aesthetically express the structural system?
More river crossings: better accessibility to the CBD
The development of new linkages and the idea of walkability across the river is a fascinating exercise. The development of several new pedestrian bridges in Brisbane could be the driver for an improvement of public space and appropriate river edge developments. Footbridges keep us fit, they link communities, cut travel times and promote exercise and healthy living. For Brisbane it represents a possibility of becoming a new model city for sustainable urban development.
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| Fig. 5: Model photo of student Wei Loh's design for a new pedestrian bridge at Edward Street. Design Studio Professor Steffen Lehmann, 2004. Total length: approx. 350 metres. |
Brisbane's bridges
Brisbane already has a series of vehicular bridges, like the characterful William Jolly Bridge (1932), or the Story Bridge (1940), which was built during the Depression as a State Government employment initiative, and was designed by the principal engineer for the Sydney Harbour Bridge, J.J. Bradfield. The steel-truss framework is in the tradition of British railway bridges, with an impressive main span of 282 metres. The first permanent Victoria Bridge, opened in 1874, was soon washed away by flood and subsequently replaced.
However, all these bridges were built more than fifty years ago.
New bridges can be unpopular until they open then they are embraced by the public. The Goodwill Bridge, opened three years ago, is a convincing argument for more pedestrian bridges. Pedestrian traffic on the Goodwill Bridge has by far exceeded expectations. Its use has meant that there are fewer cars on inner-city roads. The bridge is extremely well accepted and is crossed by 70,000 people every week. The construction of a new bridge link between Dutton Park and St Lucia, the 'Green Bridge', will be built by 2007. In addition to this, at least two more new foot and bicycle bridges are now being considered by the Queensland government.
After having explored some of the more recent elegant foot bridges in Spain, England and Germany, I would like to suggest a similar outcome for Brisbane: preferable sculptural bridges, with a minimal impact on the river views.
A recent study conducted by students in my design studio reveals the re-emergence of the footbridge: Ten examples of student works for new bridges
A research project in collaboration with transport engineers has identified five locations as preferred sites for new pedestrian crossings over the Brisbane River. In preparation for this study, several options were examined and locations identified.
There is an identified need to overcome the river, but what are the best places to cross?
The recent study and resulting publication entitled 'Brisbane Towers - Brisbane Bridges. Architecture for the City' launched by the author in December 2004, documents the research of the fifth year architectural design studio. The architecture students engaged in speculative investigations about the CBD, its relationship to the river, and improvement of its connectivity to surrounding neighbourhoods.
Students can approach this sort of project with fresh and outward-looking eyes. These students quickly realised that the design of major infrastructure elements like bridges is an important design task for architects.
The best locations: the study suggests bridges at five locations
The research points out the need for the construction of five new pedestrian and cycle bridges, and the most suitable locations that evolved out of discussions with traffic experts, local architects, transport engineers, City Council and politicians.
Much research has been done on the impact of new footbridges on neighbourhoods and traffic patterns, and if, for instance, the bridge would best utilise an existing street. The designs will need to emphasise the special character of each bridge's location.
The bridges would, preferably, have minimal suspended structures in order to keep the fine views across the sweeping curves of the Brisbane River as unobstructed as possible. However, as compensation for any change of view comes the new perspective of the river offered while using the bridge It was even suggested that new pedestrian bridges could become the venue for public art installations, like the recent temporary installation of light boxes that transformed the Goodwill Bridge during the Brisbane Festival (see Fig. 5).
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| Fig. 6: Photo of installation 'Surveillance' on Goodwill Bridge, Brisbane, 2004. Artist: Cida de Aragon. |
Conclusion
Much of the appeal of the pedestrian bridge type as a design challenge derives from its chameleon nature and the ambiguity of what such a bridge might be.
I believe a series of exciting new bridges could catapult Brisbane to the forefront of urban design. Five new landmarks! Five sculptural conceptions of the bridge.
We have always been attracted to well-designed pieces of engineering, old and new, large- or small-scale. The history of architecture is the history of making elegant structures.
The three qualities we would like to see for the new pedestrian and cycle bridges are that they be:
After advocating more pedestrian bridges for the last three years, I am pleased to see that we have entered a new phase of serious debate to strengthen the connectivity between two separate parts of the city.
References
Acknowledgements
I would like to recognise the permission of the following students to publish photographs of their work, which was developed in my design studio: Emma Termont-Schenk, Jemima Rosevear, Cameron Conwell, Kylie Draper, Nathan Hildebrandt, David Langley, Steven Harth, Cyril Jankovic, John Young, Carmen Slatter. Model photography: Richard Stringer.
I also appreciate photographs of footbridges made available by Arup Engineers (Brisbane).
Uni/RAIA Lecture 