Flowing like a river between the Avenue de France and Halle Freyssinet are the railway lines, now wider, now merging together. Here, to the right of the Panorama building, the possible area without intermediate supports is 58 meters (190 feet). Everywhere else, the buildings being erected over the railway network have been constructed on a thick platform, a table of concrete on which any collection of buildings conforming to the rules of urban development can be erected at random without planning ahead of time. Urban planners have abandoned the idea of the tabula rasa in favor of a tabula nova : a platform waiting to be developed. This approach is irrational and wasteful. Furthermore, it cannot be transposed to the right of the project because the span is too great, intermediate supports only being possible if a costly reconstruction of the rail infrastructure were to be undertaken. Our proposal approaches the problem from the other end. Instead of installing an initial platform, we have suggested suspending the platform forming the roof over the rails from the bridging building. This new theory changes the economic equation, allowing the cost of the invisible platform structure to be integrated with that of the superstructure of the building, this particular geographical arrangement allowing for a different kind of architecture. As designed, the building thus becomes a bridge-building resting on either side of the tracks, which are 58 meters apart, its 16,000 tons being suspended above the trains. The effect of this structural arrangement is liberating, making it possible to make particular use of gravitational stresses. Since the stresses are concentrated in the floors forming the bridging structure, the other parts of the building are free.
Suspended from or resting on the main structure, they can vary in thickness and embrace elements such as terraces, balconies, loggias, or mezzanines all different ways of expanding the working space depending on orientations and views.This choice of structural design makes it possible to develop comfortable tertiary spaces. The different areas and spaces extending from the office areas open onto the city or are screened from it by the use of corbelling. The working areas are able to enjoy these extensions, whether shared or individually acquired. Paradoxically, these very generous arrangements are the result of the structural constraints of the bridge design and the resolving of the problem of the railway lines by integrating the roof over the tracks into the design rather than using an inefficient supporting platform that would only increase the overall cost of the project. The architecture gains in coherence and the structure itself is implied without drawing attention to itself. Tomorrow, the railway lines below will disappear along with the whole network beneath the new construction, but the extraordinary method used will continue to evoke their presence. The beams of the main bridging are concentrated in the floors with façades pierced with a pattern recalling the Vierendeel beams used. The terraces included on the suspended or supported floors are freely varied. Both the memory of the fabrication process and that of the work site are embodied in an architecture that does not necessarily flaunt its muscles but which reveals itself without camouflage, without concealing its initial determining geographical condition. The project sprang from this coherent view; its realization becomes architecture.
REGAINING THE URBAN HORIZON
The tertiary project developed between the Bibliothèque de France and Halle Freyssinet crosses the railway lines. This is not to say, however, that it should ignore the urban landscape to which it belongs quite the opposite. In our view, the bridge formed by the project anchors it in its surroundings in the 13th arondissement, a magnificent geographical and constructed topography extending from the towers of Porte d’Italie on the horizon towards Butte aux Cailles, between the Gobelins and La Salpêtrière, and, in the distance, Ivry and Gentilly. All these places can be seen exceptionally well from the building, entering into a dialogue with it and establishing its architecture: in exchange, we offer this panorama.
The project occupies a very specific place in the development of the Paris Rive Gauche area, and particularly along the Avenue de France. To the north-east, it looks over the towers of the Bibliothèque de France, towards the Parc de Bercy, on an axis with the footbridge over the Seine. This link is particularly significant because it marks a slope in the ground here and anchors the new Rive Gauche over the roads of the 13th arondissement of the past.
Taking the constraints of the bridge-like structure as a starting point, the project aims to create new conditions of use of a tertiary building. It is the intention to enter into a dialogue with the city in relation to these new conditions of use. Our structural and morphological research has been guided by these considerations. The project seeks to take advantage of its exceptional structure more work of art than building in order to generate in turn exceptional situations. The structure required to bridge the railway lines gives great freedom of form to the envelope and, given the specific opportunities of the site and the views it offers, allows it to include places of use directed at the surrounding urban landscape: continuous balconies, double height spaces, terraces, and framed views.
THE ENVIRONMENT AS A CONDITION OF USE
We would like to see dialogue with the city as a central feature of the development of the project. The situation of being able to see out is echoed by the possibility of being seen. The building standing here is not just in alignment with others, it is also part of a remarkable perspective. The city, the horizon, the sky, and also lights and orientations are all environmental conditions, and we want these to guide the new tertiary uses put forward by the project.
The specific situation of a bridge-building makes it possible to create structures separate from the spanning elements, great bridging beams spanning 58 meters, suspended and supported elements. Thanks to the difference of these elements from the larger structures, terraces, double height spaces, and loggias can be inserted between the structural elements.
Tertiary occupation can move away from its geometrical logic (1.35 meters (4.4 feet) long by 18 meters (59 feet) wide, with an unlit central section) to discover new dimensions, varying from 6 to 19 meters (9.6 to 62.3 feet) wide, dual aspect offices, and free levels with different façades or external extensions.
It is our aim to reconsider the conditions and take advantage of the freedom offered by structures such as this to create new conditions of work in the tertiary sector. The world of offices has become too rule -bound. Here we have an opportunity to innovate, offering a variety of new, adaptable, and differentiated ways of working. Moving away from the traditional style of office, here we can create work places that open out on to the city, extended by shared spaces, horizontal spaces for socializing such as the covered terraces, or vertical balconies in the form of mezzanines. Our project opens the way and encourages new styles of working in the tertiary sector, promoting conviviality in the workplace and putting in place arrangements that bring people together under the best possible conditions.
The building makes use of the constraints imposed by its bridging structure to create variations in usage. The environmental quality here is derived from the different uses, orientations, and openings on to the city horizon. The project develops and takes shape in line with the possibilities offered by the structure for its orientation in the urban landscape.
STABILIZED EQUILIBRIUM
The need to design a structure to bridge the railways tracks below might have resulted in a compact, massive building, anchored by previously constructed supports, but we decided on a different approach. We make use of gravity, with its ability to create sophisticated groupings, constructing a framework of ribs rising from ground level, suggesting a “stabilized equilibrium”.
The load-bearing elements are of two types, with those bridging the railway below being different from those used for the transversal portals. While all the load-bearing elements are indivisibly linked, they nevertheless appear to be separate from one another. They are brought together in the heart of the building at the newel of the stairs that has the function of transferring the vertical load.
The idea was essentially to make a suspended building. The bridging structure was not simply the result of the need to span a wide area; it was also a liberating element where the directions of the protruding main beams offer multiple aspects and arrangements. Apparently disconnected, the large beams are assembled to provide portals and structural compositions, stabilized around the central newels, the structural load being taken up by two supports installed on Avenue de France and along the tree-lined walkway to the south.
We were not aiming for an extreme form of structural expressionism. We sought rather to make use of the strength of the bridging elements necessary to the project.
The structure here serves the dialogue between urban life and usage. It is the structure that liberates the panorama and that brings about a variety of usages.
The suspended mass of these large structural elements leads us to think about gravitational forces, but in a way that is more sensitive to the pleasures of the place and more generous in respect to the pleasure to be taken from being there.
The treatment of the façade is inspired by the duality of elements that support and elements that are supported. The bridging elements reveal the constraints imposed on them in a single and massive envelope pierced in a rhythm echoing the curves of the forces that run through the façade beam. The suspended or balanced parts that are fitted in between the weight-bearing volumes are an expression of an absence of constraints. Their extreme lightness is expressed in a glass skin or a simple, single curtain wall. The contrast between these two types of envelope places the weight-bearing elements in a situation of suspension.
The supports represent an important aspect of the project. They are geometrically predefined as to position and size. In order to avoid making them the most important feature of a project more concerned with its relationship to the city and the need to adapt to the scale of the passerby, the supports are integrated into an arrangement that, on the large scale, evokes a stabilized equilibrium and, locally, combines load transfer with a simple geometric form. The skill is visible but is not omnipresent. The order in which the building can be read sets it within the scale of the city.
PERFORMANCE AT THE SERVICE OF THE GENEROUS CITY
The equation could seem disturbing: a bridge building that crosses the railway tracks on 58 meters span : It is not. The structural feature is liberating!
The crossing allows to create unique spaces, freeing the offices from the constraint of the frame, freeing the user from the spatial norm of the work. The structure fixes the large spans but frees at the same time all the posed or suspended spaces which are associated there. The city offers itself as a magnificent field of view from the offices and their extensions.
According to the orientations of the panorama of the13th arrond issement and at the North the one of the Parc de Bercy, the panoptic view from the offices and terraces enter in the work place as a condition of a renovated organization. We propose with this project to set a dialogue between city and work. Pleasure of the place, pleasure to stay there, pleasure to live there.
The conditions of this recovered urbanity are composed at all scales: -
From the distant horizon of Bercy Park, between the BNF towers or down-dive from the rue du Chevaleret, level line, urban dock joining the top 13th arrondissement to the banks of the Seine.
From the Avenue de France, the corridor of aligned buildings opens here, to the sky above the building of cinemas since the planted promenade is the garden which penetrates inside the volumes in balance to offer the “internal courtyard “. The garden evokes the presence of the basement, it is not on slab but in the thickness of the soil to emerge from the heart of the crossing structure and flush with the passerby before joining vertically the terraces superimposed.
To evoke the abstraction of soil, we give it a gardenedness. This idea of a landscape environment is everywhere in the project, on all the terraces : everywhere accessible, everywhere participating in new conditions to live the place and the building. From the streets, the passerby is a resident, he can benefit from the building as a filter space but welcoming, in dialogue with the city.
The project that we propose is generous:
- generous in its way of sharing the place,
- generous in its way of offering the city and its way to be offered on all scales, always changing according to the orientations.
- generous in its way of offering new conditions of living in the workplace. We propose to take advantage of the constraint of the railways not to create a “tabula nova” absent from the territory, a slab on which would be built a building indifferent to the initial conditions.
We show here how these conditions are fertile.
