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Glass sails above a sea of forest “The idea is a cloud of glass - magical, ephemeral ..…and transparent.” These are the words Frank O. Gehry employed to introduce the Fondation Louis Vuitton pour la Création project to the public during a press conference in October 2006. “I wanted to create something that every time you approach, it shows a different character depending on the light and the time of day. I wanted to emulate everything this word ‘transparence’ means.”

The architectural model of the “Fondation Louis Vuitton pour la création“. Image courtesy of Gehry Partners.

Hired by the French luxury goods conglomerate LVMH in 2004 to realize a longstanding ambition of Bernard Arnault to create a Foundation dedicated to contemporary art in all its forms, Mr. Gehry began studies that led to the creation of Gehry Partners’ most complex project to date. The primary source of this complexity, which ultimately impacted intelligent glass solutions

virtually every aspect of the building design, was the deployment of vast glass canopies that surround the building enclosure. It is a hugely ambitious project for a sensitive site in Paris. Intensive consultations with the City of Paris, the National Sites Commission, and with the historical architects (Architectes des

Bâtiments de France) were undertaken in order to obtain the necessary building authorizations. The Sites Commission approval was conditional, with nomination of a committee to follow up and to ensure the Owner’s commitment to quality for the realization of the exterior glass elements.

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Left: Historical plan of the jardin d’acclimatation

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Right: The new plan including the foundation Louis Vuitton pour la Création

Longitudinal section – East / West

Left: The Grand Palais glass roof

Thus the stakes are very high; not only in order to satisfy the stringent requirements of the Sites Commission, but also to meet the highest demands of an Owner desiring the deployment of unprecedented technology, and an Architect who strives to “build a dream”. In this article, the authors, representing key participants in this artistic and technological adventure, tell the story of this extraordinary exploit, with a description first of the vision of a client and his Architect, then of the arduous yet rewarding conceptual and detailed study phases, and finally of the fabrication and installation of the glass elements (la verrière). It is a story marked by dedication to a compelling vision by hundreds of talented professionals, each bringing his particular expertise and production capability to a process that demanded extreme adherence to an intensely collaborative effort.

Right: The jardin d’acclimatation glass roof

ARCHITECTURE: CONCEPT & PROCESS Exceptional Site / Extraordinary Project: A New Monument in Paris The project is sited in the Jardin d’Acclimatation, amongst the trees at the northern edge of the Bois de Boulogne, in Paris. The owner’s vision for the Fondation Louis Vuitton pour la Création, scheduled to open in 2014, is to “enable a broad public to enjoy a multitude of artistic creations, deepening LVMH’s ongoing commitment to promoting culture.” It is to house and display contemporary art in all its forms. In addition to more than 3500 m2 of gallery space, the building will house a 350-seat auditorium, a bookstore, a restaurant, and administrative areas. “A vessel whose sails soar amidst the trees of the Bois de Boulogne”

The building design continues a tradition of glass architecture in Paris (The Grand Palais) and indeed in the Jardin d’Acclimatation, marked in the 19th century by the glass and steel structures of the Palais d’Hiver and the Palmarium. To meet the demanding environmental requirements for art display and conservation, the interior galleries are created from relatively simple concrete volumes. Expanding outward layer-by-layer are the side galleries, referred to as the “chapels”, and main circulation spaces. White sculptural forms, called “icebergs” in the language of the project, define this first interstitial layer. The glazed façade systems complete the enclosure of the building between these solid forms. Terraces, accessible to the public at three levels, stepping up from west to east, form the top of the enclosure. From this building envelope layer springs the primary structure of “the verrières”, or glass intelligent glass solutions

A view of the north façade (Photo by Louis-Marie Dauzat)

sails. Also referred to as umbrellas, these glass structures provide sun and rain protection to the building and its visitors. The stated intention of the architect is to allow for the visitor experience to alternate between concentrated experience of contemporary art display and moments of calm interaction with the surrounding nature.

to a lower level reflecting pool from which the building emerges. Shimmering reflections of water will animate the white iceberg surfaces and the glass sails.

While blurring the distinction between inside and outside, the glass canopies render ambiguous the relationship between building and sky.

Design Process The architectural conception and development of a project of this complexity necessitates the use of a variety of tools and methods, from the traditional to the more innovative. All must respond to the challenges presented by threedimensional complexity, during all phases and at all scales.

There is a similar attitude concerning the relationship of the building to the ground, as the building plunges below the ground plane. A water cascade slopes down, bringing water

For Gehry Partners, the early programming and design phases are carried out almost exclusively through physical study models. Once the design has reached an initial level of maturity,

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the physical model is scanned for digitalization. The three dimensional data is transferred to the BIM (Building Information Management) software, in the case of this project to Digital Project, a software developed by Gehry Technologies, and based on the CATIA software originally developed by Dassault for the design and construction of airplanes. Digital Project is a powerful tool, notably for its capacity to generate and develop complex geometrical forms. The development starts with fairly crude information (the rough data obtained by the scan of a physical model) and is refined step by step by the architects, engineers, and finally contractors, to arrive at rationalized and buildable forms. The data is exported to specialized software to 75

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RFR + TESS: engineering consulting team (Joint venture between the firms of RFR and TESS) in charge of the detailed design and engineering of the glass roof canopies (Verrières), the enclosure glass and the opaque façade system (“icebergs”) SETEC Bâtiment: Engineering consulting firm responsible for the design of the primary structure, the civil works, and of the management of the global design team and construction management

ARCHITECTURAL DEMANDS ON THE GLASS SAIL CONCEPTION For Gehry Partners, the priority of the development process of the “verrière”, needed to be focused on two main areas of research. The first was the understanding and ordering of the forms required to ensure the constructability of the surfaces that comprise the 12 sails, each one with its own geometric characteristics. What is the best method to translate these geometries, to create a module or modules that can approximate these forms? Flat panels, curved, single or variable dimensions, rectangular or parallelogram?

The Owner engaged technical assistance from Quadrature Ingéniérie, to manage and oversee the work of the design team, ensuring the viability of the project in terms of technique, cost, and schedule.

The second was to translate into reality the material intentions of these envelopes. Was the glass to be transparent, translucent or opaque; matte or glossy?

Alongside a General Contractor, it was determined that the three major packages needed early input from specialized contractors. Vinci Construction France, named as the general contractor, is in charge of the coordination and management of all the execution studies (including the coordination of the global structural model), site erection, primary concrete and steel structure construction and responsible for the global schedule and execution cost.

The data entry, exploitation, and coordination of this information for the Fondation Louis Vuitton project required the organization of an extraordinary team of individuals and organizations. Formation of a World Class Team for a Monumental Effort The unprecedented technical challenges of the project required not simply the mobilization of extraordinary talents, but the orchestration and deployment of these forces in an innovative mode of collaboration. From owner, to design team, to contractors, traditional definitions of scope and roles have been transformed in order to bring the right intelligence to the appropriate problem at the right moment. 76

In addition, given the unique monumental nature of the building, the long-term durability of the building (> 100 years) was an explicit owner requirement. And finally, a great deal of study and coordination was imposed to correctly integrate the essential technical elements: electrical, lighting, lightning protection, the downspouts, as well as the elements necessary for their maintenance.

For the glass envelopes and “iceberg” systems, SIPRAL and Hofmeister were brought on board.

3D model and 2D detail of the Verrière and iceberg interface

enable structural calculations, fire resistance simulations, and ultimately fabrication of complex elements of the building.

A view of a global structural model

As Local Architect, Studios Architecture assists Gehry Partners in the development of the project with the Paris based teams, integrating respect of local code requirement and building practices. As the Gehry Partners’ team continued to work out of their Los Angeles office, Studios Architecture primary role has been to represent Gehry Partners locally, working continually to ensure respect of the architectural design intent in the development of the detailed studies. In particular, for the glass roof system, each element, node, joint, weld, anchor, fitting, fastener, paint, seal etc. is scrupulously investigated, verified, monitored and approved by Studios Architecture before, during and after installation. Alongside Gehry Partners in Los Angeles, Studios Architecture in Paris, several world-class firms were engaged at the schematic design phase:

After a limited Request for Proposal process, incorporating not only financial and schedule commitments, but also proof of capabilities through the fabrication and installation of a mock-up, Eiffage Construction Métallique (ECM) was awarded the contract for the works of the glass canopies. Their mission ranged from the execution studies, with production drawings, productions of the different elements through to site erection. To ensure the complete realization of the works, ECM engaged several sub-contractors, including Sunglass for the execution studies and the production of the glass panels, Hess for the production of the wood beams and BEG (Bureau d’Etudes Greisch) for the structural execution studies. The Owner’s understanding of the intense collaborative requirements allowed for the creation of an optimized working environment, uniting the teams at a unique site during the high-level and highly interactive design phases. intelligent glass solutions

Metaphorical image & geometry Form, direction & tension The inspirational image is the “Class J” America’s Cup yachts with the wind aft, the billowing sails that marked the direction of these winds are in a state of tension and unstable equilibrium.

An access simulation by TAW

The glass roof complexity is not simply related to the glass objects themselves. Because the glass roofs are literally supported by the main building structure and the envelope, the complexity of the ensemble attains a diabolical level when consideration is made for dead and live structural efforts and the resulting load paths, and the penetration of primary structural elements through the building envelope (waterproofing and insulation). Provision for means and methods for maintenance and cleaning of the building surfaces brought another layer of complexity to the project. The specialized firm TAW intelligent glass solutions

performed these studies, not only for the glass canopies, but also for a wide range of interior and exterior surfaces. Finally, security and fire safety were of fundamental concern, as the fire safety code could not conceivably provide responses to previously unimaginable conditions, the specialized fire modeling and simulation experts Efectis have accompanied the project development at every phase. These diverse talents have combined to transform the metaphorical image of sails rising above a sea of forest into constructible reality.

In Frank Gehry’s conception, the headsail is to the east and under tension. The studies by the engineers of RFR and TESS required multiple iterations to achieve stability while maintaining the primary reference to “sheets and halyards” in tension. The twelve canopies that make up the Foundation are supported by elements in steel or wood. These elements which total 177 are called masts and tripods; they support the secondary frame, which is itself composed of wood and steel.

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Left: Close up on the sails of the Louis Vuitton foundation (Photo by David Guichard)

This secondary structure supports a tertiary structure composed of mullions and transoms in stainless steel. This grid provides the support, with carefully engineered attachment pieces, for the glass panels. Each of the glass sails is composed of developable surfaces; their surfaces vary from 500m² to more than 3000m², in total around 13300 m². Except for two “umbrellas” located to the West, which are composed of a single surface, the other ten are defined by two surfaces. Two lines in space, named “FOLD” and “DIAGONAL”, connect these two surfaces. The connection on the diagonal line forms an acute angle while the diagonal surfaces tend both to a nearly tangent continuity. The architectural design intent was to achieve a hierarchy and direction of the enveloping surfaces, like a sail made of fabric where the seam of the fabric reinforces and amplifies the directional reading of the surface. These guidelines on each wing print and amplify the 78

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Right: Close up on the America’s Cup yachts sails

general movement of the building. These force lines provided the guidelines for the geometric development, support structures and the definition of the layout plan of the glass panels. Once the design intent rules of the game were clearly established by the conceptual architects, there remained the challenge to find detailed technical solutions for the glass conception, supply, transformation, and installation. Perception and visual aspects of the glass An enormous amount of time, energy, discussion and study was required to translate the architectural vision of sails, transparent and ephemeral, into the selection of a defined glazing composition. To be sure, the basic architectural parameters were kept fairly simple: A basic material, glass, and the idea of white sails that would be more or less transparent. But the combining effects of several technical requirements and the

interactive effects with the environment of the Jardin d’Acclimatation required several iterations of testing and analysis of options. While the engineers of RFR/TESS were putting great talent and energy into solving the technical difficulties of the glass specification, they were also being challenged by the Owner and the Architect to synthesize the combination of parameters that would produce the desired visual effect. Among the variables that required study, testing, and recombination were the number and thicknesses of glass, interlayers, reflective coating, frit patterns, color and density. And on which surface should each treatment be applied, each with its proper criteria of manufacturing feasibility, cost, and resistance. After several months of testing and review of prototypes and samples a final selection was agreed during on-site review and after discussion between Frank Gehry and the Owner. intelligent glass solutions

Various views of the glass surfaces (Photos by David Guichard)

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A view from a terrace (Photo by Philippe Bompas)

TECHNOLOGICAL SOLUTIONS FOR THE GLASS SYSTEM Classical technical schemes

Top: On site glass prototypes review (photo by David Guichard). Left: Frit pattern definition. Right: Glass composition close up (photo by David Guichard).

Exterior to inside face of a glass panel 01 – Glass 6 mm thick 02 – Reflective coating 03 – White Frit with an opacity of 50% 04 – Sentry Glass Interlayer 05 – Glass 8 mm thick

Reaching agreement on the architectural composition of the glass was a major milestone in the design process. Yet significant technical challenges remained. The ultimate success of the project depended on the conception of a holistic system that would respond to a multilayered and multi-scaled architectural ambition: a powerful global perception of the overall forms from a distance combined with the closer scale experience of the visitor passing through the interstitial spaces behind the sails. 80

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The principal technical challenge of the glazing system results from the combination of the scale of the canopies and the highly variable and non-repetitive nature of their geometries. In theory every panel is unique. Three technological solutions, described below, have classically been put in place for projects of this nature, but none were considered entirely satisfactory A faceted solution combining trapezoidal and triangular panels is an obvious option but does not generate the desired quality of surface. Hot bent panels, formed by molding, could, in theory, perfectly match the original design surface. However, they require the production of an individual steel mold for each panel, which is economically prohibitive even if a intelligent glass solutions

Example of a double curved glass roof made with hot bent moulded panels. Left: Entrance of the Metro station Gare Saint Lazare in Paris completed in 2003. Architect: Arte Charpentier, Technical Conception: RFR, Glass Manufacturer: Sunglass. Right: View of a glass panel on its steel mould and stainless steel structure.

rationalization of the geometry into families of panels can be found. Furthermore, the fabrication process results in annealed glass, which is both significantly weaker than tempered glass and also prone to breakage due to thermal shock. Its limited resistance requires additional material thickness making the panels more rigid and thus less suited to a flexible structure.

Two technical obstacles limited the use of cold bent tempered glass for the Fondation Louis Vuitton project. Firstly certain areas of the project have very high levels of curvature. Cold bending techniques, even those of cold bending prior to lamination as adopted for the first time for the TGV train station in Strasbourg, France would result in prohibitive levels of stress in the glass. Secondly the intention was 81

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bending and their extensive experience with cylindrical tempering ovens.

Glass roof of the TGV train station in Strasbourg completed in 2007: First extensive use of cold bent layers of glass before lamination. Architect: AREP, Technical Conception: RFR, Glass Manufacturer: Seele.

Their initial work concentrated on validating the feasibility of rotated glass curving (RGC) in their bending ovens where a panel is introduced into the oven at an angle so that its direction of curvature is not parallel to its sides. They successfully established that they were capable of producing panels at an industrial scale each with a unique radius of curvature and rotation angle.

A view of one panel with an exaggerated irregular surface (in blue) and the corresponding best closest cylinder minimizing the sum of the squared distances of 8 couple of points on the edges of the panels (in yellow and red).

to support the panels on only two of their sides, and in many cases the orientation in the curvature meant that it would be impossible for the edge frames to hold the panel in shape. Innovation: Exploiting Hot bent Cylinders The search for a solution closer to the technical and architectural aspirations of the project led the design team to explore the potential of the latest generation of glass bending machines that produce hot bent tempered panels without the use of molds. The quality of tempering of these machines is comparable to that of flat glass and much better than older systems.

Because molds are no longer needed, these machines are extremely cost effective. The bending radius of the panel is controlled by computer and allows a relatively low cost for varying geometry between panels. These machines also allow the introduction of the panel at an angle relative to the axis of the machine, thus inclining its direction of curvature with respect to its edges. The principal disadvantage of the technology is that the machines are only capable of fabricating circular cylinders, which, by definition, cannot perfectly match the design surfaces conceived by the architect. The inevitable result is a discontinuity of position, tangency and curvature between adjacent panels. While it was considered

that discontinuity in curvature would not prove architecturally problematic, the steps between panels clearly posed both a visual and technological risk. Adaptation and Optimization of the Cylinders The steps between panels may be controlled by varying the geometrical properties of each panel (its radius and the orientation of its direction of curvature), and its placement (its geometrical position and angle of rotation). An â&#x20AC;&#x153;optimalâ&#x20AC;? set of cylinders must be found that limits the total divergence from the original reference surface, and by consequence the steps between panels. This is achieved by an iterative calculation process, which minimizes the sum of the squared distances of a set of points on the edges of each cylinder.

Left: A view of one sail reference surface colored by the value of the minimal curvature radius. Right: the corresponding cylindrical panelization (The central generatrixes of the cylinders are drawn in grey): this cylindrical panelization can be seen as a panel by panel curvature discretization.

A first phase optimization to establish the feasibility of the principle was completed during the early design phase. Gehry Technologies provided valuable assistance for later phases using the built in optimizer of the Digital Project software platform. The design surfaces are typically well suited to cylindrical panelization but in certain zones the approximation is less satisfactory, notably those with conical or double curvature. Geometrical solutions were tested to reduce the extreme steps, such as modification of the design surface and reduction of the panel size to create finer discretization. Neither was considered particularly desirable from an architectural standpoint and the multiplication of the number of panels had significant potential cost impact.

Left: A schematic view of a bending and tempering machine. An electric oven heats a flat pane, which then passes into a bending and tempering module, where it is continually rocked back and forth during the tempering process, leading to a good quality of tempering. Right: The inclination of the axis of the panel relatively to the axis of the machine allows fabricating curved panels whose curvature direction is not aligned with its axis.

Sunglass also commissioned an independent laboratory to complete a 40 week campaign of continuous testing to establish the quality and degree of toughening in the bent panels. This confirmed that the bending ovens of Sunglass were capable of generating a characteristic breaking strength greater than 120 MPa (fully toughened) with a high degree of uniformity that exceeded that of typical flat glazing.

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The solution envisaged at the design stage for the most problematic cases was to apply a minimal degree of cold bending to the panels on site, by forcing down one of the corners, in order to reduce the steps to acceptable levels. intelligent glass solutions

PROOF OF CONCEPT Validation by glass manufacturer and transformer The innovative nature of the glazing technology demanded a particular approach, and it was recognized early on that the support of a specialist glass transformer was essential to the process. Sunglass was chosen to assist from the very earliest stages of conception due to their world renowned expertise in glass

Prototype structural testing indicated complex bending behavior, linked to the flexibility of the edge support frames. This presented a significant logistical challenge for the structural verification of the panels, as all 3500 panels are unique both in terms of their structural behavior and the loads to which they are subjected. This naturally led towards increasing the stiffness of the edge frames, in order to give greater support to the glass and allow it to bend primarily in single curvature. This principle allowed the thickness of the glass to be optimized. The lamination of the panels also posed a technological challenge, due to the combination of bent panes with a lightly reflective soft coating and fritting. Sunglass

Left: Initial frame conception under testing, the red curves show the qualitative deformation of the glass under loading. Right: Modified frame under shock testing, red curve also show the qualitative deformation of the glass under loading.

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cylinder in space, while the top edge of the stiffener followed the theoretical design surface. This decoupling of the two geometries allowed the cylinders to float freely to suit the optimized panel geometry, while maintaining the global impression of a perfectly continuous surface.

Reference geometry = “seams sail”

Optimized 3D glazing position.

Fixing level

height variable

Left: a scheme showing the 3 different geometrical references for the glass, the cover strips fixation and the profiles fixations. Right: The same levels represented on a schematic drawing of the system.

successfully conducted accelerated aging tests to demonstrate the long term performance of the laminated complex.

• 0 under permanent loads • 0.6 under snow and wind loads • 1 under instantaneous loads or movements

The fully toughened glass was combined with an ionomer interlayer (DuPont SentryGlas). This is stiffer than a traditional PVB interlayer, enabling the two panes of the laminate to work together more as a single monolithic sheet.

The test results and analytical approach was fully documented and submitted to the French building regulation authority (CSTB) through an experimentation appreciation procedure and received approval.

The degree of collaboration between panes had not been previously certified in France, and so a further campaign of testing was launched to establish the behavior of the laminated panel. Representative panel samples were fabricated and subjected to loading of varying duration to confirm the long and short term rigidity under different temperature conditions, ranging from 20°C to 60°C.

Re-inventing glass transformation methods and tools The principal of approximating the design surfaces with floating cylinders of varying radius and rotation angles was established in the design phase of the project. However, further work was needed to refine this and develop practical details capable of adapting to the range of geometrical variation in the project.

The rigidity of the panels was shown to be very close to monolithic behavior (a monolithic factor of 1) under most conditions. Nevertheless a prudent approach was adopted and the following factors were applied in the structural verification of the panels:

One of the key details of the project is the interface between the glazing and its support frame. Sunglass, working closely with ECM, established a principle whereby the seating plate for the glazing could be fabricated to precisely follow the exact position of the

While this solution worked satisfactorily in the majority of cases, there still existed a limited number of areas where the cylindrical approximation diverged significantly from the design surfaces, creating large steps between adjacent panels. This was particularly evident in areas where the form of the design surface was either strongly conical or had a high degree of double curvature. In these cases the only option open appeared to be hot bent double curved panels or a combination of hot and cold bending, neither of which was satisfactory from a technical point of view. Confronted by this problem, Sunglass embarked on a revolutionary adaptation of one of their bending ovens, which they completely rebuilt to be capable of producing panels with two different radii – the bi-arc concept. This 15 month development effort provided a whole new range of possible panel geometries, which were able to adapt to even the most difficult design surface conditions. Furthermore, the bigger size of the new oven allowed for longer length panels, thus reducing the global cost whilst improving the architectural aspect. This level of investment in the fabrication technology was only made possible by the foresight of the client in engaging a contractor early in the process. The collaborative partnership formed between Sunglass, ECM, and the design team proved essential in the successful development and execution of the glazing system. STRUCTURAL ANALYSIS OF THE GLASS Determining the optimal glass composition for the curved panels was a complex process due principally to the variety of the panels’ configuration - their geometry, inclination, orientation, and loading. This is combined with the need to find the right balance between strength to withstand the high loads, and flexibility to accommodate the applied displacements from its supporting

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material) but also for the admissible stress in the fritted glass (short term admissible stress 35MPa, long term 25MPa). In response to this complexity, a specific methodology was developed with the contractor and the French authorities, and all the parameters required for the calculation procedure were established based on testing of representative samples. Discretization of the continuous loads measured from wind tunnel tests to a pressure by panel

frame. In these circumstances the classic engineering “envelope” approach is unsuitable. An innovative calculation method, based on interpolation, was developed to analyze each panel in order to justify the glass resistance. Geometry The panel collection consists of 3600 unique cylindrical panels over a surface of 13300m². Each has a different radius (from 3 meters to flat), direction of curvature (from -90° to +90°), inclination (from floor to façade to ceiling), and geographical location.

thicknesses” have to be taken into account for the calculations: one for the axial stress (fully monolithic), and another one for the bending stress (assuming a degree of collaboration between panes). Moreover the panels include a fritting on top of a reflective coating on face 2. Therefore the composition behavior depends on time not only for the viscous behavior of the interlayer (the longer the load, the softer the

Linking geometry and loading While certain panels are flat enough to allow verification using simple plate bending theory, the majority required more substantive calculation to accurately describe the shell action of their form. The principal parameters are the panel radius and the direction of principal curvature. Both influence the structural behavior of a panel, which is best suited to calculation by finite element analysis.

This geometrical data was stored in a panel database including: panel name, cylinder radius (R), curvature direction (α), inclination (-90° facing ground to +90° facing sky), and orientation (north, east, south, west). Loads The inclination of the panel impacts both dead load and snow distribution, which ranges from 0 to 7kN per panel. Wind tunnel tests revealed wind loads varying from 0 to 6 kN per panel due to the complex air flow around the 12 sails. Deformations of the support structure were also accounted for generating a unique warping load for each panel. Like the geometries, the loading and distortions for each panel were stored in a database. Calculating the stresses and deformations in the laminated glass Since the panels are placed above public areas, the composition must incorporate a safety glass with an interlayer. The influence of this interlayer in the stresses distributions between the glass sheets is a key parameter in the calculation process, but the classical calculation method for laminated glass is not sufficient for this project. Because of to their shapes, the panels both act in membrane-shell action and in bending. Therefore two distinct “equivalent intelligent glass solutions

Stress distribution in the glass sheets with different interlayer collaboration

Principal tension stress in the 30 panels of the matrix showing the variation of structural response to unit pressure load of 1kN/m²

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panel geometries under its own unique load condition, using only 30 finite element models.

Left: a plot of the maximum stress of the matrix panel in Z axis versus alpha and R. Right: illustration of the bilinear interpolation to get the stresses of a real panel (red) (R=8m/alpha=50°) from the stresses of the neighboring matrix panels (purple).

An obvious solution would be to generate a finite element model for each panel, but this would be prohibitively time consuming. Alternatively an envelope approach could be adopted but this would result in over dimensioning the panel thickness to resist maximum loads. This not only creates additional cost but also further amplifies the impact of the applied distortions.

In the second step the loading database is searched and the panel’s specific loading is applied. This is done by linear combination of the interpolated analysis results of unit load cases - as the glass remains elastic and movements are small, the principle of superposition may be adopted. Using this method, stresses and deformations were determined for each of the 3900 different

Further refinement of this method enabled Sunglass to optimize the composition to [8mm + 6mm] for all panels on the project. Fabrication and erection One of the fundamental challenges posed by the Verrieres is to conceive, fabricate, and erect a system with a completely non-repetitive and highly variable geometry at a scale that necessitates an industrial approach.

These very simple ideas, in reality, required an immense effort of invention covering every aspect of the Verrieres throughout every phase of the execution process. The cylindrical approximation of the glazing panels, described earlier, shows how the approach can be successfully put in place.

Digital Project 3D model of a node detail

Digital Project 3D model of the structure (Extract)

In order to meet this challenge ECM, the contractor responsible for the execution of the Verrieres, adopted a top to bottom approach of rationalization, based on two main principals: • Wherever possible, the geometry of components must be simplified to facilitate their fabrication, preferably by automated processes • Wherever possible, construction details must be capable of adapting to suit a large range of geometrical configurations

TEKLA model automatically generated from Digital Project

2D Shop drawings

The chosen method developed to verify the panels is based on interpolation, linking the geometrical database to the loading and distortion database. A matrix of typical idealized cylindrical panels has been modeled in 3D. This matrix consists of 5 columns and 6 rows of cylinders. Each row represents a single radius, R, ranging from 3m to infinite (flat panel), while each column represents the angle, alpha, of the direction of maximum curvature with respect to the short side of the panel, ranging from 0° (parallel to the long side) to +90°. Each panel of the matrix has then been analyzed in detail under unit load cases using finite element model software,

A program was developed to calculate the actual maximum stress in each panel by interpolation from the matrix, in a two-step process.

The cylindrical approximation of the panels and the planar approximation of the mullions each generate a divergence from the theoretically perfect geometry. The connection between the two systems must be capable of adapting to the range of different conditions created and accommodating these variations. One of the key principles adopted in the conception of such a detail is to develop a system which is as close to iso-static as possible. Theoretically, if the system is perfectly iso-static, it will successfully adapt to any geometrical condition. Thus the support fixings incorporate sliding, rolling, spherical bearings, capable of accommodating the most extreme angular variation seen on the project. Another key driver of the detailing of the system was the need to facilitate the erection of the glazing panels. The panel connection detail was refined to incorporate a special cast seating, which was formed to guide the panel into position as it was mounted.

The matrix thus defines 30 archetypal instances of (R, alpha) to represent the 3900 panels of the project.

First, the geometrical database is searched to find the four neighboring panels in the matrix of the panel under consideration. The mechanical response (stresses and deformations) of the actual panel are deduced from its neighbors using a bilinear interpolation in R and alpha

Another critical example is the conception of the mullions of the glazing support system. The project requires around 10km of these elements, which theoretically should all be doubly curved and twisted. In this case their geometry was typically approximated into a series of single curved planar elements. Through this simplification ECM was able to exploit CNC cutting techniques of plate elements to define and control the individual geometry of each mullion. They also invested in the development of robotic welding techniques, which not only created significant practical advantages but also enhanced the visual quality of the fabrication.

Progress in the construction of the bow sails (Photo by Philippe Bompas)

Glass fixation detail; Left: Transversal section, Right: Longitudinal section

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The whole philosophy and approach to managing the geometrical complexity was based on a foundation of modeling the entire package in three dimensions. The project software platform, Digital Projects, was well adapted to this effort, particularly through its capabilities for parametric modeling. The investment of this effort paid significant dividends, especially as ECM developed a fully 87

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Fo n d a ti o n L o u i s Vu i t to n C a s e St u d y

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integrated approach, linking the geometrical model with their fabrication software. The approach was further extended to manage the vast logistical effort of identifying, marking, and delivering every individual component of the Verrieres.

Installation of the top sail, one of the most difficult (Photo by Louis-Marie Dauzat)

Transom assembly machine (specific development)

The challenge of the project was met by a concerted approach to refine and develop the geometry and detailing of every component of the glazing system to optimize its fabrication and erection. The value of this rigorous and exhaustive approach is best illustrated by the clear success of the erection phase of the project. CONCLUSION

Gusset assembly machine (specific development)

Glass installation (Photo by Mohamed Khalfi)

Spline welded section assembly

Welding robot with 5 axes welding head

As we witness the final hoisting of the glass sails of the Fondation Louis Vuitton in the Bois de Boulogne, it may be too early to celebrate. Yet there emerges a certain collective satisfaction that the team has exceeded the challenge. Viewed from afar, from up close, from within, in winter and in spring, sunny days, cloudy days, with rain, snow or frost, the glass canopies provide for a marvelously varied experience each and every visit. It began with the vision of a client. An owner who not only understood that exceptional efforts would be required, but that innovative strategies would also be required to deploy, structure, organize and coordinate those means. An owner that was uncompromising on the demand for a project of the highest quality.

Node assembly and welding

Trial assembly of a beam in shop

To build the dream of the architect required nothing less than the complete collaborative commitment of individuals and organizations willing to go beyond classic definitions of roles and interactions. Architects, engineers, consultants, suppliers, contractors, project managers; for the project participants it has been an adventure and a discovery. The path to realizing the cloud has been … magical, ephemeral..… and transparent.

Geometry control (with 3D theoretical model superposition)

Trial assembly in shop of 1/3rd of the first sail

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Contributing Authors James Cowey Studios Architecture AIA - Principal, Paris An architect with over 25 years of experience in both France and the United States, James is a former member of the Board of Directors of the AIA Continental Europe Chapter. He continues to be involved in the AIA CE, conducting site tours of STUDIOS’ projects for the chapter and members. James has contributed significantly to the firm’s presence in Europe, expanding the practice beyond the workplace to include residential, cultural, and civic projects, as well as repositioning some of Paris’ oldest buildings. Benedicte Danis Setec Batiment After interventions as civil engineer specialized in structural design and calculations for important building such as the rehabilitation of the Mariinsky Theater in St Petersburg and the Louis Vuitton for the Creation Foundation, Bénédicte Danis is now working as Project Manager for Setec Batiment. She’s doing technical coordination for the complex project Louis Vuitton Foundation during the erection phase, with a focus on the glass roof “Verrière”. Benedicte is graduate of Ecole Polytechnique and Ecole Nationale des Ponts et Chaussées two of the best Engineering Schools in France. David Guichard Studios Architecture Architecte D.P.L.G In 2009, David arrived at Studios Architecture to follow in the development and construction of the Fondation Louis Vuitton. David started his carrier in boat design with a creation of sail boats, monohull and multihulls. After this particular experience, he came back in the architectural field and develops buildings in the domain of Public facilities/Culture, Towers/Commercial & leisure, Office & Industry. He is also teaching at the “Ecole Nationale Supérieure d’Architecture de Paris La Villette (ENSAPLV)” since 1999.

A recent view of the sails approaching completion (Photo by Philippe Bompas)

Jacques Raynaud RFR Trained as an architect and structural engineer, Jacques joined RFR in 1993. His work focuses on geometrically complex structures, developing constructive geometry and technical solutions. Jacques is also a very experienced CAD user and script developer. He’s a member of the research project ARC – Architectural Freeform Structures from Single Curved Panels, which links RFR, Vienna University of Technology and Evolute in an Industry-Academia Research Partnership. Simon Aubry T/E/S/S Engineer, Ecole des Mines de Paris MA., Ecole des Ponts et Chaussées As a multidisciplinary engineer, Simon is interested in facades and complex structures, often associated with innovative architectural projects. His knowledge of structural design and material science, and 7 years work experience in engineering firms (RFR and T / E / S / S) allow him to cover multiple topics, interacting with both the Architects and the Contractors. Within the design team for the Fondation Louis Vuitton project, Simon is in charge of the design, development and calculation of curved facade panels: in laminated glass for the canopies and in high performance Concrete for “the ICEBERG” facade. He teaches a Structural Design course at the Ecole des Ponts & Chaussées since 2009. Valérie Boniface Eiffage Construction Métallique Civil Engineer, Ecole des Ponts et Chaussées As a structural engineer, Valerie is interested and specializes in complex steel structures. She has been in charge of the design team of Eiffage Construction Métallique for 7 years after 8 years as a structural engineer in RFR. In Eiffage Construction Métallique, she has contributed to the development of BIM and 3D global approach for design, fabrication and site assembly. Valerie has been teaching steel construction at the Ecole des Ponts & Chaussées since 2008.

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Gery Chinzi Sunglass A Chemist Graduate, more than 25 year experience in glass processing industry. After 15 years in a glass manufacturer center of Research, developed the High speed train curved glasses composition (TGV 2 level and ICE 3. He has been in charge of many sales projects within Sunglass for 8 years.

intelligent glass solutions