Flying over the rails.

FLYING OVER THE RAILS A pavilion on the outskirts of Haarlem

by Despoina Papadopoulou

Delft University of Technology Faculty of Architecture Master in Architecture, Urbanism & Building Sciences Architectural Engineering: Design Research Studio Course code: AR3AE010 Academic Year 2010-2011, MSc3 Course Coordinator: Ir.J.F.Engels Building Technology Instructor: Frank Schnater

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Contents

preface. a research-driven design introduction

Site analysis. a

The need for a cycle flying-over

The Pavilion’s architecture. b

A “light” structure communicating with the user-visitor

research topics

Architextiles a “Textile tectonics and Soft Constructivism” b Responsive Architecture c

prime research questions

Light-emitting mesh a

- The electronic devices

A new structural morphology type by carbon fiber material b - Strong and liquid

Harvesting energy from vibrations c - The piezoelectric effect

Light-emitting mesh d - The fabric mesh

designing the pavilion

Structural analysis - Why sandwich material?

The bridge - A textile vessel A responsive textile mesh Founding the pavilion Flying over the rails

conclusions literature study

a b c d e

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preface This report presents the results of the research that was done during the first quarter of the MSc3 semester, for the Design Research Studio. The main focus of the course is to coordinate engineering questions and architectural design, introducing the relation and balance between research and architectural design. Therefore, integrating the findings of the research into the design of the particular project was the leading point and not functional or conceptional aspects as in many cases.

The project involved the design of a pavilion located along the canal –railway axis that connects Haarlem with

a research-driven design

Amsterdam city, near the Oostpoort of Haarlem. The specific research questions which would be implemented in the design were chosen individually and answered with the guidance of a specialized Building Technology teacher and the main architect coordinator.

The results of this interdisciplinary approach together with the site analysis will raise the starting point and the (new) research questions for the Graduation Project.

Kustwaarts map, Arcam Publicaties, 2009

Aerial phtographaph of Spaarnewoude Station

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introduction a.

Site analysis.The need for a cycle flying-over

The site for the pavilion is part of the general area undergoing development called: Kustwaarts. This area, the coast triangle between the cities of Ijmuiden, Zandvoort and Amsterdam was brought to the forefront by an exhibition of ARCAM held on summer 2009. This versatile piece of land comprises of successive landscapes, cultural heritage places, urban areas, industry and recreation. The sequence of fields reveal traces of the past and at the same time a glance into the future. This is not a unique example. Similar situations of suburban areas under pressure due to urban sprawl and port-industrial development exist everywhere in Netherlands.

A glance at the map of Kustwaarts created by ARCAM makes clear that most development occurs along the margins; those are the banks of the North Sea and the railway line between Amsterdam and Haarlem. But besides the already finished developments -like the Sugar City- or the planned ones, there are also the unknown future developments

RIGHT Cycling over the rails

that will follow the general trend towards further densification. It is exactly on the site along this crucial line between Haarlem and Spaarnewoude Station where the pavilion had to be located, inclining towards the changes to take place.

The railway between Haarlem and Amsterdam was built in 1839 and it was the first railway in the Netherlands. Until then the axis was a waterway, with boats and large ships being the main connection and transport means. It was not before 1920 that cars were introduced and later on dominated the transport sector.

Today one can see along the axis the combination of the three strip elements: rails, water and motorway lines running the distance between the two cities. As it can be easily observed, the cross passing of the pedestrians and cyclists isn’t facilitated by these traffic venues.

Particularly for cyclists, the distance between connections is long. That is why the decision of a pavilion having the function of a cycle flying-over was made.

A light arched spans bridge sketch

Building over the rails

A responsive pavilion-bridge

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b.

The Pavilion’s architecture. A “light” structure communicating with the user-visitor.

A pavilion is usually a free-standing structure, an object of pleasure, a space dedicated to relaxation and view. Contemporary examples have given additional uses to such structures: gathering, playing, experiencing, sensing, communicating, passing over-through-under, consuming, presenting, exhibiting, performing etc.

The decision of designing a cycle flyingover route in relation with the pavilion was followed by the image of a gate for the city of Haarlem; a pavilion that would generate awareness of the changeable and unstable character of the area. The user/visitor is here the “voyager” but also the spectator. The first one has a sensorial voyage passing the bridge over the pavilion and the second experiences the responses of this event imprinted on the pavilion itself. This interaction brought to the front of the research the topic of responsive architecture.

RIGHT The Spiral. Sheffield parkway bridge proposal

Commonly adjectives like “ephemeral”, “light”, “mobile”, accompany the type of a pavilion’s architecture. The dynamic character and the functionality of the case in question described above were to be combined with the aesthetic values of a light structure. This was partially due to the realization of the vagueness of the characterization “light” itself and a desire to further research on it. So what is considered light in architecture? It can be a façade “liberated from weight”, a structure the load-bearing elements of which is reduced to minimum or even merely a sketch having a light impression. But how can a design incorporate all these aspects? Textile architecture was promising to give an answer.

Subsequently to these two lines of responsive and textile architecture, the question of how to integrate, attach or embed responsive elements in a light – textile structure was of a prime importance.

Snowdon Aviary, London, Lord Snowdon, 1965

Rosa Parks Transit Center, FTL Engineering Studio, 2009

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Olympiastadion, Munchen, Frei Otto, 1968

research topics a.

Architextiles

One of the aims of the pavilion’s design had the scope of stretching the notion of a textile/fabric architecture and open up to known and new territories of research.

New cultural, entertainment and leisure habits raise new architectural questions to be answered through a more adaptable, interactive, multimedia functional and dynamic architecture, driving the search for new architextile forms and aesthetics. Accordingly, the ever-changing typology of a pavilion seems a fertile ground for this research to be developed.

communicative and multifunctional spatial design. The unique aesthetics of the textile design and their ability to embody a composite range of dynamic characteristics like lightness, flow, flexibility, skin, complexity, transparency and movement go with the flow of architecture’s shift towards a less static state. Architects, designers, engineers, theorists and materials specialists working nowadays on new methodologies of fabricating or in better words: weaving space, challenging the traditional practices.

“Technology” and “textile” both derive from the Latin “texere” which means to weave, to connect or to construct. Architextiles was the title given to the special edition of the magazine Architectural Design of November/December 2006 communicating the contemporary trend of a more networked, dynamic, interactive,

In contrast with the discrete content of fabric architecture of the last decades, textile -like light- can have a variety of interpretations: knitting together unexpected materials, applying textile techniques, sculpting woven or other kind of textilelike spatial structures, creating tensile surfaces or forming porous buildings etc.

ABOVE Multihalle Mannheim, Mutschler Architects, Frei Otto, Ove Arup, 1975 RIGHT Rosa Parks Transit Center, FTL ES, 2009

Embroidered out of suture thread, this piece of textile would be sandwiched in an artificial shoulder joint.

The starburst shape, 5.75 inches wide, allows the surgeon different options for securing the joint in place.

Vascular graft of woven, crimped polyester with bovine collagen is used in aortic surgery

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Apan’s Sakase Adtech triaxial carbon fiber fabric

But even textiles are themselves multidimensional: membranes, nonwovens, meshes, agglomeration of fibers, fabric composites and other hybrids. Exhibitions like “Extreme Textiles” at the CooperHewitt, New York (2005) and “Skin and Bones” in the Contemporary Museum of Modern Art, LA (2006-07) and projects like the recent Expo Swiss Pavilion or the NOX architects’ Maison Follie are representative of this variety and reveal “a textile way of thinking” (Lars Spuybroek).

Advances in biotechnology, nanotechnology, electronics, 3-D weaving, shape memory alloys and biomimetics helped greatly to new material science and technologies offering extraordinary properties and high-performance products. For example, new materials such as glass, ceramic and carbon fibers, aramids, liquid crystal polymers and high-modulus polyethylenes are able to perform under extreme forces and combined into composites. The unprecedented and surprising range of properties of such supertextiles means they are not only able to substitute and surpass older materials, but are offering “a new materiality to architecture” (Mark Garcia, AD, 78).

Diller + Scofidio’s Brain Coat (2002) for their artificial Cloud ‘Blur’ in Switzerland, Enric Ruiz Geli’s Hotel Habitat (2006) and ONL’s kinetic architectural experi-

ments such as ‘Muscle Body’ (2005) and the Textile Growth Monument in Tilburg (2005) have all combined new intelligent materials and interactive technologies with textile techniques.

Socio-cultural and economic changes also contribute to this shift towards textile architecture. This is because conventional architecture proves to be too slow to keep up with the speed of changes in needs and/or in culture. For Herzog & de Meuron, fashion’s speed presents an interesting paradigm for architectural practice: “in the world of fashion … things move faster than in architecture – getting dressed, getting undressed, transforming oneself, giving shape, trying out new sculptural possibilities, examining the quality of surface texture, inventing a new style, and discarding it again.” Having the same logic of immediate response to the need of clothing the body, sprayon technology, demonstrated in London in 2010, creates a seamless fabric that may have applications in medicine as well as fashion. Manel Torres, a Spanish designer, joined forces with scientists at Imperial College London to invent the spray which allows for clothing that can be worn, washed and worn again. The spray consists of short fibers that are mixed into a solvent, allowing it to be sprayed from a can or high-pressure spray gun.

ABOVE Textile Growth Monument in Tilburg, Ilona Lénárd, 2005 MIDDLE Son-o-House, NOX Architects, 2004 BELOW Maison Folie, NOX Architects, 2004

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Metabolic Media metal netting with embedded printed OLED’s, L.E.Walker, M. Gmachl, for the London Design Festival 2008.

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A recently developed category of textile materials are the electronic textiles.

These are energy harvesting skins that interact with the environment in different ways, depending on the technologies and materials used. As it was mentioned above, one of the basic lines followed for the design of the pavilion was its interaction and particularly its responsiveness to the environment-users. The other was the lightness of its structure. The creative approach of electronic textiles and the innovative interactive spatial qualities they can offer were thought adequate for this reason. Moreover, their textile, lightweight nature contributes to the light image desired for the pavilion and that is why they consist part of this research.

There are two main categories of electronic textiles. In the first one the electronic devices/energy harvesting materials are attached on textiles while in the second they are embedded into them. As it concerns the first category, the relative new materials most commonly attached to textile skins are the Solar Cells. These can be Silicon (older version), Thin Film, Organic or Dye Solar Cells (dye as absorption material) which are the latest version. Although DSC have a low cost production, a fabrication that includes environmental friendly materials and an overall lightweight and flexible quality, they have a relatively lower efficiency, planned to increase to 10% in the future (still two times lower than Silicon Solar Cells).

RIGHT ‘Solar Ivy’ Photovoltaic Leaves, SMIT, 2009

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However, the initial idea of the pavilion demanded that it would interact with the users-voyagers of the bridge and not essentially with the environment, in the case of DSC with sunlight. That is why the research diverged from the solarenergy harvesting devices into other electronic devices that could respond emitting light with the adequate supply of energy. Such electronic devices that can be easily attached on textiles are LEDs. Inspired by the ambience of the sheltered meshed environments of Dominique Perrault and Ryohei Koike’s and Jarod Poenisch’s nested skyscraper, preliminary sketches were drawn to present the concept of an interactive/responsive meshed landscape. The deviation of rigid forms and the blur distinction of spaces behind or in the front of these live skins were qualities to be gained.

LEDs (Light-Emitting Diodes) are semi conductor light sources. When a LED is switched on and electric current passes through them, electrons are able to recombine with holes within the device, releasing energy in the form of photons, in other words emitting light. This effect is known as electroluminescence. The color of the light is correspondent to the energy of the photon and is determined by the energy gap of the semiconductor,

not by the plastic body. LEDs present many advantages including lower energy consumption, longer lifetime, improved robustness, smaller size and greater durability. The most up-to-date version of LEDs are OLEDs. These are Organic Light-Emitting Diodes whose luminescent material is composed of two layers of organic compounds. But these devices are still vulnerable to humidity. One of the precedents paradigms is the Hotel Habitat, by Cloud 9. The hotel consists of a building with an energy harvesting mesh wrapped around it. This mesh collects the sun’s energy during the day by individual nodes that at night give off a specific color according to the collected energy. It consists of 500 tri-color LEDs controlled by a PIC microprocessor. Also imbedded in the model’s mesh are photo-sensors which determine the brightness on them and give off a color according to the energy color scheme.

This model was created for the exhibition “New Spanish Architects” at the MoMA in New York, Feb 2006. This piece is now part of the MoMA’s permanent collection.

The question set then for further research was how to attach LED/OLED devices in the case of the bridge-pavilion on its textile mesh and is discussed in the next chapter (a,d).

ABOVE “Garibaldi station”, D. Perrault MIDDLE Mariinsky Theatre, St. Petersburg, D. Perrault, 2007 BELOW Hotel Habitat, Cloud 9+ J.Clar, 2006

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b.

“Textile tectonics and Soft Constructivism”

“Architectural design is not about having ideas, but about having techniques, techniques that operate on a material level. It’s about making matter think and live by itself.” Lars Spuybroek Inspired by the work of NOX architects and their textile-way of creating structures, the research moved from the micro tectonics of textile surfaces to building tectonics that have been created through textile techniques: weaving, braiding, knitting, interlacing etc.

Some early sketches showing the desire of applying textile techniques to create structural surfaces where the initial “yarns” become surfaces; surfaces become geometry and geometry structure. Even at a more aesthetic level, space can be created by undulating surfaces-sheltering the user as shown in the last sketch of the woven cages.

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The contrast between the lightness/softness and the strength/hardness of this type of architectural design fitted well in the frame of a light, interactive –so maybe flexible- pavilion that had to be strong enough to hold the bridge but not totally unaffected by forces. Further researching on how the macro tectonics of the pavilion could come from the micro tectonics of a textile technique led to a large amount of contemporary architectural examples. Each deployed a different technique and materials.

Lister Mills, David Morley Architects.

_Translucent epoxy and stainless steel: Metz project, NOX architects. _Steel curved members and double glass elements: Jalisco Library, NOX architects. _Double curved clad in metal sheet adjusted on wooden structure. Main structural elements of steel: Housing

It was then seen as a challenge to research on a way of employing carbon fiber material to weave a structure for the pavilion. This is the second of the prime research questions which will be described in detail in the next chapter (b).

However, apart from the scale of buildings, the same logic is often apparent to smaller scale design. Three particular furniture projects had a great influence to the progress of the research. Except from the evident textile character of the first two, all of them share the same material: carbon fiber.

The Bench by Peter Donders, the chairs designed by Mathias Bengtsson and last the Seoul Table by Z.Hadid.

ABOVE Carbon Fiber C-Bench, Peter Donders, 2010 Made by twisting carbon fibers around a piece of molded foam, and then removing the foam.

MIDDLE The Spun Chairs, Mathias Bengtsson,2010 Produced using spun carbon fiber, a material used in helicopters and medical prostheses, and weighs 2.2 pounds.

BELOW Seoul Table, Zaha Hadid, 2008

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c.

Interactive architecture covers emerging architectural and artistic practices where digital technologies and virtual spaces merge with tangible spatial experiences.

An active architecture, sensing, observing, feeling, listening, thinking, reacting, proposing, adapting, interacting is in constant flux. Responsive architecture is about spaces that react – respond to the surroundings’ stimulants. This response can have many interpretations depending on the goal to be achieved.

It can be a response after a measurement of actual environmental conditions to enable buildings to adapt their form, shape, color or character responsively.

OPPOSITE PAGE TOP A pavilion designed to change the shape of its skin like the billow and flow of a parachute blowing in the wind, by Tristan d’Estree Sterk at The Office for Robotic Architectural Media & The Bureau for Responsive Architecture AND BELOW A responsive skin to the sunlight.

Responsive Architecture Examples of façades, bridges, and movable structural members of spaces give an idea of the different scales on which responsive architecture can be applied.

Responsive architectural practices distinguish themselves from other forms of interactive design by incorporating intelligent and responsive technologies into the core elements of a building’s fabric.

In the case of the designed pavilion, color and light emission as well as the movement of the structure itself that responds to the vibration caused by the users are the basic responsive elements which are further answered in the next chapter.

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prime research questions a.

Light-emitting mesh - The electronic devices

As presented before, the resurgence in lighting has been led by developments in small molecule and polymer-based organic molecules that emit light when subjected to an electrical current. Unlike inorganic semiconductor based LEDs, organic LEDs can be deposited over larger areas and on flexible or non-planar substrates. However, the light emitting organic molecules tend to degrade and are vulnerable to humidity and oxidation.

A new method developed involves coating a blue LED with Quantum dots that glow white in response to the blue light from the LED. Quantum dots incorporate the best aspects of both organic and inorganic light emitters. This method emits a warm, yellowish-white light similar to

that made by incandescent bulbs. Quantum dots are semiconductor nanocrystals whose emission color can vary from the visible throughout the infrared spectrum.

This allows quantum dot LEDs to create almost any color on the CIE diagram, so they can be tuned to emit light over a larger color gamut. Moreover, they can be processed over large areas using liquid phase deposition techniques including roll-to-roll process, printing, and spin coating, providing better color rendering than white LEDs and larger color variety.

Except of the devices that will react and emit light, the mesh itself that hosts them had to be decided. But even before that, the structural body of the pavilion had to be first resolved.

b.

A new structural morphology type by carbon fiber material - Strong and “liquid”

This project was seen as an experiment; an inquiry into the role of structure in the production of space. Material and structural types are chosen to produce the architectural form. But what is determinant of the other depends on the case.

Sometimes the problem an architect has to solve demands for a specific structural typology, when other times the use of a particular material is crucial due to transfer costs or availability. This has led for some kinds of designs to be imagined for /materialized with well-known materials that have been “tested” in similar projects. Carbon fiber materials are usually used until now for cladding, smallscale elements with demands in high strength - low weight and less often as a structural material. This project aims at an innovative strategy that will meet the challenge of coordinating structure and carbon fiber material to produce experiential effects and aesthetic qualities.

1.

Carbon fiber material characteristics.

Carbon fibers are of 0.005-0.010 mm diameter strands of carbon atoms in crys-

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tals. Several thousands of fibers twisted together form a yarn which can be either coated with plastic resin or be woven into a fabric. Images of these types Carbon fiber is a relatively new material which demonstrates a high strengthto-weight ratio, a lower than steel density combined with a low thermal expansion. The stiffness of a material is measured by its modulus of elasticity. The modulus of carbon fiber is typically 138 GPa and its ultimate tensile strength is typically 3.5 GPa. Thus it can be up to five times stronger than steel when manufactured correctly.

In the design process it is critical that the behavior under loading is understood and accounted, particularly in terms of design safety factors. Therefore is noted here that solid carbon fiber will not undergo plastic deformation (yielding). Under load carbon fiber bends, but will not remain in a permanently deformed state once the load is removed. Instead, once the ultimate strength of the material is exceeded, carbon fiber will suddenly fail.

When designing composite parts, one cannot simply compare properties of carbon fiber versus steel, aluminum, or plastic, since these materials are in general homogeneous and have isotropic properties throughout (along all axes). By comparison, in a carbon fiber part the strength resides along the axis of the fibers, and thus fiber properties and orientation greatly impact mechanical properties. Carbon fiber parts are in general anisotropic.

The strength to weight ratio (as well as stiffness to weight ratio) of a carbon fiber part is much higher than either steel or non-reinforced plastic. The specific de-

tails depend on the matter of construction of the part and the application. For instance, a foam-core sandwich has extremely high strength to weight ratio in bending, but not necessarily in compression or crush. In addition, the loading and boundary conditions for any components are unique to the structure within which they reside. Thus it is impossible to provide the thickness of carbon fiber plate that would directly replace the steel plate in a given application without careful consideration of all design factors.

This is accomplished through engineering analysis and experimental validation.

OPPOSITE PAGE From top to bottom: a 6 Îźm diameter carbon filament, carbon nanotubes, woven carbon textile, carbon tube, bidirectional carbon fiber tape.

RIGHT Comparison of materials’ strength.

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Applying the idea of weaving bands

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2. Peter Testa’s Carbon Fiber Tower.

As it was mentioned before, the exhibition “Extreme Textiles” of CooperHewitt’s museum presented highly engineered fabrics having extraordinary performance. They are divided in 5 categories: faster, lighter, stronger, safer, or smarter materials. Much of the exhibit focuses on the textiles’ agricultural, aerospace, military, and industrial uses.

But the most astonishing exhibit was Peter Testa’s Carbon Tower. This 40 story skyscraper is constructed by 40 carbon fiber helical bands formed by pultrusion in continuous helix. These bands,

which are a foot wide and an inch thick, take the vertical compressive load. The 40 floor plates of 38m diameter are tied with the external structure in tension, preventing the helix to collapse.

This concept of carbon fiber use pushes the design frontiers for architectural constructions. Its phenomenal lightness and strength made it ideal for spacecraft, Formula 1 cars, and tennis rackets, so what about architecture? Interpreting the construction logic of the tower to the pavilion – bridge is presented in the following sketch.

RIGHT Carbon fiber tower, P.Testa, exterior and interior view.

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3. Solid, yet liquid.

The goal of this research regarding the materiality of the pavilion is to reveal a compelling solution of using carbon fiber not like hidden reinforcement but as the main exposed material, providing inspiration for a new approach to design. The cast carbon fiber composite Seoul Table was set as a paradigm for the designing of a solid, yet liquid, pavilion.

Experimenting with continuous structures that tangle, split and meet again to shape the supports of the bridge, led to a series of sketches that proved to be more ran-

dom and form-finding driven than desired.

The seductive possibilities of double curved surfaces in computer modeling have made them a formal phenomenon in contemporary architectural practice. However, the tools used to realize constructions aren’t always capable of meeting the challenge. Selecting a complementary and suitable realization strategy plays a pivotal role. Therefore, before developing the design, it was considered beneficial to research on how exactly these types of forms are or can be manufactured.

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4. Cast carbon fiber - Molding Proceses.

Carbon fiber material like most of the composites can be processed by many different techniques depending on the properties of the desired result. Pultrusion, (as for Testa’s Tower), vacuum bagging or infusion, Hands or Spray lay-up are some of them.

Because of the forms that the pavilion is tuned, two of the processes were considered more suitable and therefore were studied and compared.

Hand lay-up is the simplest and oldest open molding method of the composite fabrication processes. It is a low volume, labor intensive method suited especially for large components, such as boat hulls. Glass or other reinforcing mat or woven fabric or roving is positioned manually in the open mold, and resin is poured, brushed, or sprayed over and into the glass plies. Entrapped air is removed manually with squeegees or rollers to complete the laminates structure. Room temperature curing polyesters and epoxies are the most commonly used matrix resins. Curing is initiated by a catalyst in the resin system, which hardens the fiber reinforced resin com-

posite without external heat. For a high quality part surface, a pigmented gel coat is first applied to the mold surface.

Vacuum/Resin infusion utilizes a vacuum bag to debulk or compact a part’s complete laminate ply schedule of reinforcements and/or core materials laid onto the mold. After debulking, the resin is allowed to be infused by the vacuum to completely wet out the reinforcements and eliminate all air voids in the laminate structure. High quality composite parts made from a wide range of fiber and resin combinations can be utilized to infuse laminates up to six inches thick.

Typical resins used are polyester, vinyl ester, and epoxy with many being UV cure initiated. This process can routinely produce large 2,000 sq. ft. parts such as boat hulls, bus bodies, and railcar panels. This processes added benefits include eliminating weaker secondary bonds and reduced VOC emissions vs. current open molding processes.

Pigmented gel coats provide the parts surface finish and often a hand lay-up skin laminate may be fabricated to allow fabricators to walk on gel coated surface while loading the dry reinforcement laminate ply schedule and vacuum bag. page

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5. The example of carbon fiber artificial members

The last decade, carbon fiber technology is being used for the production of a vast series of artificial members for prosthesis. Prosthesis is the replacement of a missing limb or part of a limb. With prosthesis, movement and mobility is enhanced and enabled. Furthermore, lately there have been examples of athletes acquiring artificial members that have been customly designed to comply with activities like recreational jogging, trail running, marathon running and triathlon.

Taken the example of a particular mod-

el (Flex-Run, Ossur company), energy storage and release, is a function inherent in the design as well as vertical shock absorption. (Vertical forces generated at heel contact are stored and translated into a linear motion.)

The same way that this patented device deals with the impact and loading of the human body and movement, the designed pavilion’s bands would carry the load of the bridge and the circulation of the users. Some preliminary sketches show the way they could play the role of the bridge’s supports.

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6. Pavilion’s structural typology: tangled ribbons.

Integrating the paradigm of the artificial carbon fiber members to a light, continuous form, ended in a structure where space is created by undulating ribbons which both support the bridge but also shelter the visitor underneath. The construction is possible with using vacuum infusion and hands kay up processing. What is the appropriate thickness however of the ribbons remains to be researched. A description of the pavilion and bridge’s structural behavior follows in the next chapter.

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c.

Harvesting energy from vibrations The piezoelectric effect

The idea of storing energy from the movement of the pavilion-bridge led to the research of materials that can actually mutate the vibrations to energy. Such materials are the piezoelectric materials.

Piezoelectricity is the materials’ ability to convert mechanical stress into electrical energy. It derives from the Greek word piezein (“πιέζειν”), which means to squeeze or press, and electron (“ήλεκτρον”), which stands for amber. The effect was discovered in 1880 by the brothers Jacques & Pierre Curie. A piezoelectric disk generates a voltage when deformed The piezoelectric effect is understood as the linear electromechanical interaction between the mechanical and the electrical state in crystalline materials with no inversion symmetry (in such a space group for every point (x, y, z) in the unit cell there is an indistinguishable point (-x, -y, -z)). The piezoelectric effect is a reversible process, thus materials that exhibit it also exhibit the reverse: the internal generation of a mechanical force resulting from an applied electrical field.

There are a lot of materials that possess piezoelectric properties. In most cases the effect is quite small and therepage ।39

fore not suitable for energy harvesting.

There are some materials however, both natural and man-made, that possess stronger piezoelectric properties.

Natural occurring piezoelectric crystals are: Berlinite, Quartz, Rochelle salt, topaz and Tourmaline group minerals. Other natural materials are: bone, tendon, silk, wood, enamel and dentin.

Man-made materials include: gallium orthophosphate (GaPO4) and Langasite (La3Ga5SiO14).

The most common used piezoelectric materials are ceramics like lead zirconate titanate, also known as PZT. There are also some polymers like Polyvinylidene fluoride (PVDF). The advantage of polymers in comparison to crystal and ceramics is that polymers are more flexible. Where crystals and ceramics can only change shape for a small amount (less than 1%), while PVDF can stretch for 25%.

After researching both on the performance and environmental impact of such materials, lead-free piezoelectric materials were chosen. This is because there is a recent growing concern regarding the toxicity in lead-containing devices.

To address this concern, there has been resurgence in the compositional development of lead-free piezoelectric materials.

More detailed, the chosen material here is PZT, lead zirconate titanate, is a ceramic material that was developed at the Tokyo institute of technology in 1952. It is commonly used in sensor and acoustical applications. PZT is a brittle material that barely changes shape when a force is applied. This makes it a suitable material to use under pressure conditions. Images Precedent examples in architecture include applications on floors. Club WATT in Rotterdam consists of square floor composite elements which harvest the every dancing person produces. The 30m2 of dance floor produce enough energy to generate 10% of the clubs energy demand. More recently even, in 2009, the East Japan Railway Company announced the installation of piezoelectric elements in the floors of its Tokyo station in an attempt to generate power from passengers passing through ticket gates. The power-generating floor covers an area of 25m squared and is installed at 7 ticket gates and 7 staircase steps inside the gate. 1,400 kW/sec pro-

duced each day is used to power ticket gates and electronic display systems.

It is easy to understand that the performance of the piezoelectric devices of the pavilion is favored by its public character and function as a bridge, as traffic passing is the best way to generate vibrations. These can be ultimately converted into energy by being transferred to the support points. A softer soil surface will transfer vibrations better than a harder soil. Also a bumpier surface will cause the traffic to generate more vibrations. The amount of vibrations produced also depends on the connection to the ground. When something is suspended it will absorb more of them. The stiffness of the floor elements will determine how much of the vibrations’ amount will be transferred to the support points.

Consequently: a.

The piezoelectric materials chosen were lead-free ceramics, the shape and dimensions of which will be shown in the next chapter. b.

They were located on the connections between the bridge surface and the upper surface of the pavilion. c.

The surface of the cycle way was designed as a series of blocks of materials and not continuous, in order to be bumpier.

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d.

Light-emitting mesh - The fabric mesh

As shown in the adjacent image, the carbon fiber ribbons spinning around and holding the bridge structure are connected with wires. This way an enclosure is created that determines the more sheltered and more open places inside the pavilion but also a stimulating sequence of textile and solid surfaces over the cyclists – passengers of the bridge.

However, a mesh can have many images depending on the material used and on its density, geometry, assimilation technique, color etc.

The initial concept for the mesh as shown roughly in the next sketches was to weave around the basic wires: a) colorful ropes, b) led strips and then spray-up similarly with the technique mentioned for fashioning clothes, c) waste carbon-fibers with resin.

An interesting example of fabrication of a similar textile mesh is the Windshape Pavilion. Windshape was an ephemeral

structure commissioned by the Savannah College of Art & Design as a gathering and event space near their Provence campus in Lacoste, France. Built by N Architects and a team of SCAD students over a period of five weeks, it was conceived as two eight-meter-high pavilions that dynamically changed with the power of wind. A vine-like structural network of white plastic pipes, joined together and stretched apart by aluminum collars, fifty kilometers of white polypropylene string threaded through the lattice, all together created swaying enclosures.

The string was woven into dense regions and surfaces and pinched to define doorways, windows, and spaces for seating.

What was decided was: a. To use the already mentioned metal wires with special joints connection on both edges in order that they are adjusted on the slots/holders of the surfaces of carbon fiber structures. b. Metal hooks should be welded per distances on these wires in order for c. Fabric ropes are woven between them.

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designing the pavilion a.

Structural analysis - Why sandwich material?

As it was mentioned in previous part, it is impossible to provide the thickness of carbon fiber plate that would directly replace a steel plate or section in a given application without careful consideration of all design factors.

This is accomplished through engineering analysis and experimental validation.

Before further developing the design of the carbon fiber bands, it had to be decided if these would be solid or composite. The structural mechanics analysis that follows showed that the sandwich panels are better in stress distribution.

A composite sandwich combines the superior strength and stiffness properties of carbon-fiber with a lower density core material. By strategically combining these materials, one is able to create a final product with a much higher bending stiffness to weight ratio than with either material alone. Composite sandwich structure is mechanically equivalent to a homogeneous I-Beam construction in bending.

Referring to the picture of the sandwich structure, at the center of the beam (assuming symmetry) lays the neutral axis, which is where the internal axial stress

equals zero. In Figure 2, moving from bottom to top in the diagram, the internal stresses switch from compressive to tensile. Bending stiffness is proportional to the cross-sectional moment of inertia, as well as the material modulus of elasticity.

Thus for maximum bending stiffness, one should place an extremely stiff material as far from the neutral axis as possible. By placing carbon fiber furthest from the neutral axis, and filling the remaining volume with a lower density material, such as wood, foam, or honeycomb, the result is a composite sandwich material with high stiffness to weight ratio.

For the construction of the pavilion, it was decided the use of foam for the inside layer. There are several types of foam available depending on the application. Foam volumetric density can range from as low as 16 kg/m続 to over 961 kg/m続. High density foam cores provide greater resistance to compression and crush, as well as provide damage tolerance from impact. Low density foam cores with carbon-fiber face sheets, particularly in thicknesses greater 2.5 cm, can produce panels with extraordinarily high stiffness to weight ratio. A medium density foam is prefered in this case.

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Then, the live and dead load of the bridge had to be investigated. The load F is the input of the design while the thickness of the composite’s layers and the length l of e eccentricity as shown are the output, thus the

factors that the design is dealing with.

The calculations showed that as the desired thickness of the composite is decreased, the thickness of the carbon fiber layer should increase.

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The Pavilion’s tangled ribbons were the first to be drawn in Rhino, taking under consideration the results of the previous structural analysis.

This way, as the thickness of the ribbons is changing organically along their length, the magnitude of stresses applied is revealed.

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Initial sketch. The bridge here consists of different elements for each function: pedestrians’ path, cyclists’ path, balustrade and supports on pavilion’s ribbons.

Creating a feeling of enclosure along the bridge. The idea in the sketch on the left is achieved in a more geometrical way while the second one is a textile solution, using rods fabric net.

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b.

The bridge - A textile vessel

For designing the bridge, 4 basic elements had to be taken under consideration: a) the pedestrian and cycle path material, b) the balustrades, c) the supports/connections on/with the pavilion and d) the main structural element that will allow the spanning presented on the sketch plan.

Rather than adopting a more con-

RIGHT Woven interlocking ropes around the metal truss.

BELOW View from the cyclist’s pont of view.

servative concept of assembling different parts for the different needed elements (as in the previous sketch), a more unifying approach was preferred.

Inspired by examples like the MĂśbius bridge in Bristol, or the more conceptual Loophole bridge by Marc Fornes and R&Sie (n), the designed was oriented into a continuous textile vessel.

3.

2.

1.

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The bridge’s elements, as thought in this stage were: 1. curved as a C-shape steel sections 2. metal wires that tight the steel sections together 3. fabric bands weaved in situ between the wires This solution which is presented here in the sketch and it was further detailed, is problematic to certain aspects. a. The fact that the bridge is curved doesn’t allow for tension between the steel ele-

ments through the wires to exist. That would mean an instable structure constantly wanting to “open” as the following scheme shows. b. The steel plates designed in the detail, aren’t adequate because they are not able to span for 7 meters (between the HSS shown in plan) without bending . If this solution is to be applied, they must be replaced by an I-section steel beam. c. The piezoelectric ceramic material was initially designed as a tube and placed symmetrically in a short distance from the central axis of the bridge.

But the results would be greater if two plates of material is located under the I section beams.

Initial detail section piezoelectric tube

piezoelectric surface

Detail section after improvements

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Vertical section a-a

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a

a

Plan of the pavilion. A pedestrian way made by concrete blocks continues from the edge of the ramp until the Station’s platforms.

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Inspired by the previously described carbon fiber C-Bench by Peter Donders, the idea of a carbon fiber bridge made out of C-shaped ribbons was developed.

The surface of the bridge, a perforated curved vessel was trimmed by a sequence of surfaces, in a pattern that repeats itself every some

meters, just enough for the pattern to appear random along the bridge.

Shadows, fragmented views and lighness were the qualities achieved.

The composite carbon fibre ramp is resting upon a hollow steel section, same way with the previous design solution.

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A space for gathering, sensing, experiencing, exhibiting, passing by or visiting. A light structure, challenging the demands of both its material and function, is constructed in the environment as weaving it.

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In order to decide whether the spanning of the ramp is feasible and to design an appopriate section, a rough structutral analysis had to be done.

For the arc-beam we assume the equivalent straight beam from support to support (40m), but as distributed load we consider the total length of the arcbeam (100m) and then convert it to distributed load for the “equivalent� beam.

The itenary process of design starts by assuming a tubular beam CHS. The structural steel strength and the plasticity capacity of the steel (category 2 in order for the total structure to be more durable) are also selected.The moment capacity is found by tables of standarized CHS (here from the Corus software-the blue book).

It is checked whether the selecte moment capacity is greater than the moment caused by the loading at the end of the fixed-fixed beam (Med=1/12*ql^2) assuming that the shear force is smaller than 50% of shear strength.

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Night view

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c.

As it was desribed previously, taken by the example of WindShape pavilion, the mesh created between the carbon fibers is composed by metal ropes with adjusted special hooks in order for the thinner fabric ropes to be woven - stiched between them.

Then, a layer of sprayed fabric is applied with spray-guns. The mixture of crosslinking cotton fibers, polymers, resin and a solvent becomes a textile sur-

RIGHT 1. Metal wires 2. The connections of the metal wires to the carbon fiber bands with the adjusted piezoelectric ceramic 3. The hooks through which the fabric ropes are woven 4. Colorful fabric ropes 5. The sprayed mixture of fibers that becomes a textile surface

A responsive textile mesh face when sprayed and can meet various demands of properties and textures.

The main metal ropes which “tie together� the bands, have a piezoelectric material adjusted on the edges.

This way and as vibrations are created from the cyclists or pedestrians’ passing, electricity is produced.

When the amount of energy harvested is enough, the embedded quantum LEDs are stimulated and emit light.

d.

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Founding the pavilion

e.

Flying over the rails

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conclusions The initial inquiry into the role of structure in the production of space was researched through the application of the relatively new carbon fiber composite material into a design that tries to stretch the limits of material’s possible forms. Taking under consideration the results of the rough analysis of the pavilions structural behavior, the challenge of coordinating the material to the design is achieved.

The resulting design of this research studio combines both experiential effects and aesthtic qualities.

However, it is necessary to add that this is meant to be only a concept project as there are two main reasons that would prohibit its realization. First of all the economic expense is immense compared to same scale but different materiality designs. Second of all carbon fiber is the least sustainable material of both steel and aluminium and its recycle isn’t yet practised.

Furthermore, the sprayed fabric technology used here for the interactive mesh hasn’t been tested in outdoor climate. Although it is an important factor about the feasibility of the project, It is out of the scope of this research to conclude to a more precise proposal about the spray mixture.

In the future, material and fabrication technology shall meet with such a design.

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literature study ARCHITEXTILES Architectural Design Magazine, Volume 76, Issue6, November/December 2006 TECHNIQUES AND TECHNOLOGIES IN MORPHOGENETIC DESIGN Architectural Design Magazine,Volume 76, Issue2,March/April 2006 DelDOT BRIDGE DESIGN MANUAL, Chapter 4, Bridge Load Rating EVALUATION OF COMPOSITE SANDWICH PANELS FABRICATED USING VACUUM ASSISTED RESIN TRANSFER MOLDING S.A. Smith, et al., 2000 ELECTRONIC TEXTILES Ifigeneia Dilaveraki, 2010 PIEZOELECTRICITY IN ARCHITECTURE Arjan Klem, 2009 ADVANCES IN ARCHITECTURAL GEOMETRY Vienna, September 2008, Conference Proceedings THE PAVILION. PLEASURE AND POLEMICS IN ARCHITECTURE Edited by Peter Cachola Schmal, Hatje Cantz, 2009

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