· TEXTILE IN INTERIORS Spain TENSILE ROOF ORCA OCEAN SHOW Spain TEXTILE RIVER OVER...

N E W S L E T T E R O F T H E E U R O P E A N B A S E D N E T W O R K F O R T H E D E S I G N A N D R E A L I S A T I O N O F T E N S I L E S T R U C T U R E S

NEWSLETTER NR. 16APRIL 2009PUBLISHED TWICE A YEARPRICE 15€ (POST INCL)www.tensinet.com

First prototype of a foil façade of equal frame modules covered

with mechanically pre-stressed foil

ETFE Façade

ARTICLE

PROJECTS

RESEARCH

Italy TEXTILE IN INTERIORS

Spain TENSILE ROOF ORCA OCEAN SHOW

Spain TEXTILE RIVER

OVER PARTICIPANTS'STREET

FAILURE OF FABRIC REINFORCED MEMBRANES

&INDUSTRY SUPPORTED PHD

TENSINEWS NR. 16 – APRIL 20092

Ceno Tecwww.ceno-tec.de

Dyneonwww.dyneon.com

FabricArtMembrane Structureswww.fabricart.com.tr/

Form TLwww.Form-tl.de

IMSwww.ims-institute.orgwww.membranestructures.de

Messe FrankfurtTechtextilwww.techtextil.de

Mehler Texnologies www.mehler-texnologies.com

Taiyo Europewww.taiyo-europe.com

Saint-Gobain www.sheerfill.com

technet GmbHwww.technet-gmbh.com

Verseidagwww.vsindutex.de

W.L. Gore & Associateswww.gore.com/tenara

form TL

Ferrari sawww.ferrari-textiles.com

Canobbio S.p.A.www.canobbio.com

partners2009

INFO

Buro Happoldwww.burohappold.com

PROJECTS

ARTICLES

RESEARCH

PA G E

9 LITERATURE New Tent Architecture -ETFE Technology and Design - Kengo Kuma

24 PRESS RELEASE Good design award 2008 3 awards for FabriTec Structures Westfield Wondon

MISC

n°16contents

PA G E

4 Australia MAKMAX AUSTRALIATransformation into a Green Void

5 Spain BAT BURO ARQUITECTURA TEXTILTextile Mall Parque Almenara

6 Italy UNIVERSITÀ DI NAPOLI FEDERICO IITextile in interiors

10 Spain COMERCIAL MARITIMA L&ZARENAS & ASSOCIADOS

Tensile roof Orca Ocean Show

19 Spain LLORENS A circular paraboloid The Castle

20 Spain ESCRIG & SANCHEZTextile river over participants' street

23 Germany CENO TECFloating Roof

PA G E

12 ETFE FaçadeFirst prototype of a foil façade of equal frame

modules covered with mechanically pre-stressed foil.

Bad Tölz, Germany

PA G E

14 FAILURE of fabric reinforced membranes

A yarn based modelling approach

18 INDUSTRY SUPPORTED PHDstarted at Newcastle University A pragmatic approach

to determining the mechanical behaviour of structural fabrics.

Editorial BoardJohn Chilton, Evi Corne, Niels De Temmerman, Peter Gosling, Marijke Mollaert

CoordinationMarijke Mollaert, phone: +32 2 629 28 45, [email protected]

Address Vrije Uni ver siteit Brussel (VUB), Dept. of Architectural Engineering,Pleinlaan 2, 1050 Brus sels, Belgium fax: +32 2 629 28 41

ISSN1784-5688

All copyrights remain by each author

Price 15€ postage & packing included

TENSINEWS NR. 16 – APRIL 2009 3

Edito Since the last TensiNews issue both an Annual General Meeting (10th November, Stuttgart)and a Board Meeting (2nd February, Brussels) have taken place.

In Stuttgart fifty one TensiNet members attended the lectures, the Annual General Meeting and the Working Group Meetings and afterwards visited Labor Blum. During the Partner Meeting the new board was elected: Heidrun Bögner-Balz as Chair, Bernd Stimpfle, John Chilton and Stefania Lombardi as Vice-Chairs and Marijke Mollaertas Executive Secretary.As agreed during the second Partner Meeting in 2006 the class of Founding partners does not exist any longer. Partners pay the full 2400€ membership fee. A new class of Associate partnershas been introduced: these are the Working Group Leaders, the Schools and Universities which actively contribute to TensiNet’s daily work and “small firms” which are invited by the Partners according to their specific expertise.During the Partner Meeting it was proposed to choose for the next TensiNet Symposium an Eastern European country. The exact location is not decided yet.

The next Partner Meeting is planned on Monday the 15th of June just before Techtextil 2009(Frankfurt from 16th till 18th June). The Working Group ETFE (Rogier Houtman) will meet the sameday. The Student Award ceremony takes place on the 15th in the evening. The Working GroupDisaster Relief will be activated. Caroline Henrotay (VUB) will coordinate this Working Group.

During the Board meeting it was decided that the TensiNet Association should put extra effort into increasing the number of TensiNet members: all current members should contact candidatemembers they know personally. TensiNet should promote its Working Groups, should publish articles in local professional magazines and become more visible during events, fairs and symposia.To support these actions a new TensiNet flyer is available athttp://www.tensinet.com/files/General_information/FLYER_2009_2.pdf

From now on individual issues of TensiNews, with the renewed layout, will be on sale at the price of 15€. New issues will be announced on the website with a table of content. Abstracts of importantarticles will be put on the website with a reference to the corresponding TensiNews on sale. National and local professional magazines will be informed about the renewed TensiNews.

A proposal for the standardisation of “materials, fabrication and installation of membranes” has been sent to the standardisation communities (TC 250) of the European countries as a first step in establishing a EUROCODE. National representatives are Juan Monjo and Ignasi Llorenz forSpain and Portugal, Roberto Canobbio and Alessandra Zanelli for Italy, Matti Orpana for Finland and the Scandinavian countries, Marc Malinowski and Françoise Fournier for France, Heidrun Bögner-Balz, Bernd Stimpfle and Henric Leuer for Germany, Marijke Mollaert for Belgium, Rogier Houtmanand Arno Pronk for The Netherlands and John Chilton and Peter Gosling for the United Kingdom. They will follow up the handling of the proposal for a EUROCODE.

The Annual General Meeting 2009 will be held on the 30th of September during the IASS 2009conference in Valencia. Joint to the Annual General Meeting the results of the Working Groups will be presented and interesting recent projects completed by TensiNet members will be reviewed. A slideshow will be made and afterwards put on the website.

With this short summary of meetings, discussions and future action points we hope to reinforce the presence of Tensile Surface Structures on the market and to strengthen cooperation in research.

Marijke Mollaert

Forthcoming Events International conference TEX TEH II - 2009 Bucharest, Romania 07>08/05/2009 www.certex.ro/

conference_texteh2.htm ● International exhibition & conferenceROOF & CLADDING INDIA 2009 Mumbai, India 28>30/05/ 2009

www.roofindia.com ● Workshop Textile Roofs 2009 Berlin, German y 11>13/06/2009 www.textile-roofs.com ● International Trade Fair

& SymposiumTechtextil 2009 Frankfurt, Germany 16>18/06/2009 techtextil.messefrankfurt.com ● Symposium IASS 2009 Valencia,

Spain 28/09>02/10/ 2009 www.iassvalencia2009.com ● International ConferenceStructural Membranes 2009 Stuttgart, Germany

05>07/10/2009 congress.cimne.upc.es/membranes09

WORKING GROUP ETFE meetingTechtextil 2009 Frankfurt, Germany15/06/2009�13:30 - 15:30

Partner MeetingTechtextil 2009 Frankfurt, Germany15/06/2009�15:45 - 17:45

Annual General MeetingIASS 2009 Valencia, Spain 30/09/2009

The Annual General Meeting will consist of 2 parts: Recent projects by TensiNet members will be presented first,next the board will report on the realizations,the WG-activities, the financial situation and the future objectives.

Calls ICSA2010

1st International Conference on Structures & Architecture

Guimarães, Portugal - 21>23/07/2010

Call for Mini-Symposia & Special Sessions > before 30 April 2009

Call for Abstracts> before 31 May 2009

Call for Associated Events > before 30 June 2009

Forthcoming Meetings

Sydney Customs House has rolled out the green carpet to unveil a uniqueaddition to its architectural history. It has been given an ultra-modernedge with a futuristic yet organic 3D structure known as the “Green Void”,the latest collaboration between MakMax and Chris Bosse of LAVA.

The lightweight Lycra sculpture hovers within the Customs House atrium,taking in Café Sydney’s top floor position stretching to the model ofSydney incased in the glass floor at ground level. The translucent fabricallows ample amounts of sunlight through from the atrium some 5 floorsabove creating a surreal experience as the surroundings take on a limegreen glow. At night the structure is illuminated to take on the look of lavabubbling up from a volcano.

MakMax and Chris Bosse have previously worked on projects such as theMoet and Chandon Marquee and POL Oxygen stand and more recently theMTV Music Awards set but nothing could compare to this most recentcollaboration. This is the most ambitious Lycra structure they have ever attempted. Beinga heritage listed building many challenges were faced in the design process.They had to create a surface floating in space, supported by a heritagelisted façade which they were not allowed to permanently anchor to, aswell as support a fixed fabric edge that was not excessively heavy. The endresult is a credit to the engineering design, patterning and fabricationprocess.

The project shows a new way of digital workflow, generating space out oflight weight material in an extremely short time. The computer-modelfeeds directly into the finite element software for generation of true fabricform which marries with the manufacturing process.

Lycra has been given new life with applications such as custom designedfabrics that stretch the possibilities of modern architecture. The fabric is astandard 80% Nylon/20% Lycra which is sourced from a manufacturertraditionally to dealing with dancewear manufacturers.

With sustainability being at the forefront of every architect’s designconcept MakMax has been leading the way with bespoke tensilemembrane structures and use of minimal materials. The total fabric weighsa mere 45Kg and is stretched over 12% past its original size to create itsfinal shape. The use of such fabric allows it to be folded and fit inside asports bag, yet has enough elasticity to fill a volume of 160m3. The totalsurface area is 233m2. Minimal amounts of Aluminium and hardware werea necessity to enhance the fabrics natural curvature. The fabric issupported by only five rings. The complete structure including theAluminium edges weighs 210Kg.The form was taken from an architectural model developed by LAVA.Utilizing force density shaping and elastic analysis the final shape wasfound to complement ring supports. Intricate patterns limited by the 1.5mfabric roll width create the structures form. Cutting patterns weredeveloped through scribing geodesics through the structure at strategiclocations and flattening using an energy method more able to handle thehighly curved surface. The riggers dubbed the structure ‘Shrek’s ears’ whichis a great example of digital media being translated into fabric design.The Green Void oozes charisma and will remain on display until mid 2009.

� Daniel Cook� [email protected] � www.makmax.com.au


Transformation into a Green VoidSydney Customs House, Australia

A temporary construction until mid 2009

MAKMAX AUSTRALIA

Name of the project: Green Void Location address: 31 Alfred Street, Circular Quay, NSW 2000, Australia Client (investor): Sydney Customs House Function of building: Cultural Centre, Library, restaurant, office building Type of application of the membrane: SculptureYear of construction: 2008 Architects: LAVA (Laboratory for Visionary Architecture) Multi disciplinary engineering: ARUP Structural engineers: MakMax Australia Consulting engineer for the membrane: MakMax Australia Engineering of the controlling mechanism: MakMak AustraliaTensile membrane contractor: MakMax Australia Manufacture and installation: MakMax Australia Material: Lycra Covered surface (roofed area): 300m2


Food courtFor the food court, three big conicalroofs were planned in order tocreate vast shadows. At the lowerpoints the membranes areanchored on the roof of the mallstructure and the tops aresupported by three main masts -one for each roof. The overlappingof the three membranes wasdesigned to create a more dynamicvisual result. As an immediateoutcome of these ideas and alsodue to the size of the roofs (eachone of the two smaller structures is800m2 Ferrari 1202 and the biggestis 2.000m2 Ferrari 1302) high loadsappeared. This requires a highprestress (more than 2.000kN insome cases) and hence a strong

primary structure and heavy dutycables. The final result still seemslight within the large spans (in thecentral roof more than 60m).All the masts and cables wereplaced exactly on the appropriateconcrete pillar heads: some of theanchorage points on the slab werereinforced with additional steelframes and thicker slabs so that theload transmission was correct.Steel plates for masts and cableswere installed during the executionof the slabs, to assure a high qualityload transmission. Some of theseplates did weight over 800kg.The prestress in the membranesand tie down cables wasintroduced in two ways. At thecorner points special turnbuckles

were used and at the top of themain masts the position of afloating ring connected to the topwas adjusted by tensioning withhydraulic devices. Each membrane was plotter cutand welded into one piece (eventhe 2.000m2 one) in our factory,and crane folded in a precise way toallow an easy unfolding on site, atthe right position.Cable sizes did not allow usingreasonable pocket borders, so aclamping system was designed toallow the installation of the clampsand the cables on the ground, andthe uplifting roof by roof in onlyone operation.Time needed for the installation ofthe food court roofs was one month,two weeks for the biggest and oneweek for each one of the smaller.

RestaurantTen more roofs were built for aspecific restaurant. They weredesigned as inverted cones ofabout 80m2 each, with an eccentricmast, and were manufactured in

the workshop and installed in avery fast way since all the systemworks as a modular kitconstruction. Membranes werepatterned, plotter cut and made inour factory in Ferrari 502 colouredfabric. Installation process on sitetook only one day per roof.

Bowling terraceFinally a 600m2 roof was designedand built for the bowling terrace,following similar criteria than in the food court ones.An articulated central arch createda significant shape in the middle, so it was easy to reduce loads onthe membrane and the structures. This roof was made in Ferrari 702,and its geometry and size alloweda common pocket border solution,so the complete roof was designed, engineered, built andinstalled in only 1 month.

� Javier Tejera, José Javier Bataller and Marian Marco (architects)

� [email protected]� www.buroarquitecturatextil.com

Textile Mall Parque Almenara

Name of the project: TEXTILE MALL Parque AlmenaraLocation address: Lorca, Murcia, SpainClient (investor): Desarrollos Comerciales y de Ocio LorcaFunction of building: Shopping CenterType of application of the membrane: sun protectionYear of construction: 2008Architects: OAU-ImaginespaciosMulti disciplinary engineering: LV SalamancaStructural engineers: BAT • Buro Arquitectura Textil & Form TLConsulting engineer for the membranes: BAT • Buro Arquitectura Textil & FormTLTensile membrane contractor: BAT • Buro Arquitectura TextilSuppliers: Ferrari, Horfasa, CYE - S. MoñitaManufacture and installation: BAT • Buro Arquitectura Textil & Montage ServiceMaterial: Ferrari 1302, 1202, 502, 702Covered surface: >3.000m2

Lorca, Murcia, SpainLorca is one of the hottest places in Spain. In fact people from site say as a

joke Lorca means “calor” (hot) upside down. There are more than 300 sunny days per year, and the average temperature is 20ºC.

So the goal of the open-air mall was to create shaded places with asignificant decrease of tem pe ra ture, to make it comfortable.

BAT BURO ARQUITECTURA TEXTIL

4

3

1 2

1

2

Figure 1. Overlapping of the roofs

of the Food court.

Figure 2. The roofs of the

restaurant designed as inverted cones.

Figure 3. The roof of the

bowling terrace

Figure 4.Areal view

U N I N A


In the work for the interiors of thelibrary “Pisanti”, carried out andrealized in 2002, the installation isinspired by the Parthenopeanvolcano, also in its name “Vesuviolibri”; it is originated from the ideaof a symbolic analogy with thevolcanic eruption that in thisproject becomes production anddistribution of culture. The visualanalogy is possible thanks to theability to create with membrane ashape that remembers an upside-down volcano, so books go outfrom its mouth, in the same time it

features thespace and it

creates anoriginal internalcovering for the sale

room. The installationof covering in an “upside-downvolcano“ belongs to a larger projectthat includes interior placing formany bookshop locals, in whichwas provided design and realizationof exhibitors for book-sales anddifferent typologies of sails, thathave functions of covering andfurnishing for interior rooms.The bookshop is organized indifferent functional areas, thatare entrance, multifunctionalarea, communication area,storehouse and specific exhibitionareas (Figure 1). Common andunifying vaulted tenso-structure

elements were provided fordifferent rooms. They havedifferent dimensions and radiusesin order to adapt themselves to thegeometry of the rooms; moreover,the structure of sails is also utilizedto support canalizations for theplans and in order to regularize theheight of rooms. Another specificfunction of the membranestructures in this work, thanks tothe translucence of fabric, is

supplying useful reflecting surfacesfor lighting the rooms, in order toimprove visual comfort in interiors;furthermore a detailed study wasmade for the right collocation ofthe lights that illuminate books onsale and for the internal paths froma room to another.In this work the fabric called TB Cottonfire C1, composed of 55% cotton and 45% modacrilicowas employed; the weave is

constructed from Ne 20-2 yarns in the warp

direction (30 threads/cm) and Ne 8-1 yarnsin the weft direction(20 threads/cm); the Cottonfire fabricweighs 360gr/m2

and its width is195cm. Moreover,

UNIVERSITÀ DI NAPOLI FEDERICO I I

Textile in interiors

INSTALLATION “Vesuvio libri”at the library “Pisanti”, S. Giorgio a Cremano, Naples

1

1

In membrane architecture, we don’t talk enough about textile in interiorarchitecture and furnishing, in particular about its wide possibilities inapplication of innovative systems of interior envelopes and partitions.Textile materials can contribute to articulate many different spaces,residences or offices, exposition spaces and showrooms, and generally inevery occasions in which flexibility and constructive reversibility representessential objectives: furnishings, shows, fashion parades, musical andartistic or cultural installations, commercial or fair manifestations,ceremonies or parties and so on.

Lightness and translucence of membranes, together with constructiveelements in aluminium, steel or wood which act as supports, areproperties that make effective application of textile elements and systemsin furnishings and interior architecture or in creation of temporary,removable or transformable installations.

Stretch textile materials are often utilized in interiors. In fact they havemany invaluable qualities for this use. Stretch textiles take the form independence of locations of supports and also of applied tensions, so theymould directly on anchorage points; in different cases stretch textilesavoid difficult problems in design with fabrics or membranes, that are thequestion of form-control and the other question about cuts of fabrics, sowhen installations have small dimensions it’s possible to solve theseproblems. In fact, the problems of cuts and assembly between differentparts of fabric remain essential questions in large projects or installations,

in which membrane is cut and then it is assembled; another essentialproblem is about modelling, that is realized and controlled by constructionof mock-up, three-dimensional scale models or virtual simulations.

Textile membranes have a grade of elasticity that varies according tocomposition of material; in particular, it can vary from 3% to 30% till200% of elongation for stretch membranes, besides when elongation isgreater the translucence of membrane becomes greater too.Stretch fabrics, like cotton, nylon, polyester, contain a variablepercentage between 3% and 30% of an elastic polyurethane fibre that iscalled spandex or elastan.

Among stretch fabrics for interiors, Nylon has excellent mechanicalqualities, high coefficient of elasticity, toughness and resistance toabrasions or lesions and impacts. Moreover, Kevlar is a fabric that isincluded in particular class of special Nylon; it has high resistance totractions and impacts, furthermore it has a unique combination ofqualities, as resistance to warm and fire or as high absorption of vibrations,that has allowed designers and constructors to find answers for manyproblems, which are esteemed hard to solve in field of organic fibres.Moreover, today fibre in PTFE (polytetra fluo roe thylene), with trade-markTEFLON, is very often used because of its excellent qualities aboutmechanical, thermal and chemical stability; another excellent fibre-mix isPTFE and glass, with trade-mark TEFAIRE that is a good and innovativealternative, also in order to have economic benefits.

1


the finish is applied throughimmersion with fluorocarbonicresin with processing Scotchgardand “Sanitized”. The sewing parts offabric were cut according to thegeometry of the graphic design andmade ready. Assembly ofinstallation consists in joiningturnbuckles together with steelcables that are fixed at anchoragesin the walls of thebuildingstructure.Connections areat a height thatallows regulatingthe tension of thefabric in order toobtain the correctspatialconfiguration ofmembrane

structure. On one side fabric has apunctual anchorage at perimetricwalls, on the other side it isanchored in four points at a steeldisk that is fixed at the exhibitor ofbooks thanks to a steel hook. The base of upside-down volcanocoincides with the middle of theroom, where the different parts offabric are connected through steel

connection systems at the supportstructure, so the membrane takesdesigned shape and lets you seethe internal side of textile volcano,while light can pass through textilecovering (Figure 2). In this way, the diffuse lightthrough the membrane wasutilized together with the light that is projected from lamps onto

the external surface, so it ispossible to have more light in the room. In conclusion, the membrane covering alsoevokes lunettes on wallssurrounding the room, which are decorated with pictures ofParthenopean Volcano, fromGoethe’s work to contemporaryartists’ works (Figure 3).

Figure 1. Sketches for the installation of “Vesuvio libri” at

the library “Pisanti”.

Figure 2. 3D design of the “Vesuvio libri”.

Figure 3. Interior view ofthe “Vesuvio libri”.

Name of the project: Vesuvio libriLocation address: Villa Bruno, S. Giorgio a Cremano, Naples, ItalyClient (investor): Società Renato Pisanti srlFunction of building: LibraryType of application of the membrane: Up-side down cone structureYear of construction: 2002Architects: Aldo Capasso and Alfonso Mauro, Carmen Terracciano (collaborators)Structural engineers: Baku Group, NaplesManufacture and installation: Salvatore Sessa, NaplesMaterial: TB Cottonfire C1Covered surface: 56m2

Cost: 6000€3

2

Furthermore, textile materials present very interesting behaviour inrelation with light; in fact, all stretch fabrics or plastic membranes havedifferent properties of light transmission, reflection and absorption, sothey can generate particular lighting effects, for instance making surfaces,that can be external envelopes or interior partitions in architectonicspaces, on which solar radiation filters and through which artificial lightingis modulated. In design of interior architectures, textiles contribute torealize flowing and soft spaces, whether for lightness of elements or fornatural luminosity of materials, in particular when they are applied indivision of different spaces with different functions, or in staging forexpositions and events that request original visual effects.

On international scene of design with textiles for interiors, protagonistsare American designers, architects or engineers, and also manufacturingcompanies that have experimented with use of fabrics in variousoccasions. In particular, Transformit projects, produces and installsstructures for interiors with tensioned fabrics; another American companyis Dazian, which supplies a wide range of stretch fabrics able to open upnew horizons for interior architectures, for instance directing attention totextile scenographies that give possibilities of different pleasure grades formany performances with visual originality. Among international designstudios, FormTL, a German engineering firm, is particularly active in textiledesign, because of its large experience in textile design and membranestructures; moreover, American designer Gisela Stromeyer uses stretchfabric “spandex” for many and different installations; she works with avariety of options for fabrics, that can be translucent or transparent,coloured or white together with particular lighting effects.

In Italy the use of textiles in interior architectures is not enoughwidespread yet, also because of insufficient presence of studies with

specialization in textile design and few operative industries or companiesfor production, supplying and manufacture of membrane structures.Another impediment to larger diffusion of membrane architecture in Italyis due to the lack of a normative reference, in particular for big coverings,external envelopes and large constructions, which are more subject to theproblems of structural safety and stability, resistance to weather or fireand so on.

Among the architects who pay more attention to the possibilities of usingtextiles in architecture, Aldo Capasso distinguishes himself by a wideresearch work about membrane architecture, in the Laboratory ofLightness Technologies in the University of Naples, and moreover by someprojects that exalt textiles for their versatility and their inclination forfitting out or furnishing the interior.

These works, thanks to the use of a fabric like cotton fibre, articulatespaces with different features in order to add modern value, operating onpre-existent elements with different modalities: in historic and artisticscenes textiles add an innovative accent in a light way without any graveinvasion; while, in places of new constructions textiles exalt spatialpeculiarities giving character to rooms or scenes, underlining a dimensionor a perspective rather than another architectonic element and are able todesign new shapes of spaces. So these works become emblematic ofdesign modalities that answer to different needs: one of these works ispermanent furnishing and the other are temporary fitting-outs. The firstone of these works is the design of interiors for the library “Pisanti”, in S.Giorgio a Cremano (Naples); the second one is the fitting-out for the prize-giving manifestation in Camera di Commercio in Naples and the last one isthe installation for the exposition about “Impresa Donna”, both located ina central room of the Palazzo della Borsa in Naples1.

Membrane architecture


For the fitting-out of the prize-giving manifestation in the Cameradi Commercio in Naples (2002) atensioned textile was realized,which was located in the middle ofthe room like a tensioned structureto cover the protagonist place ofthe manifestation. The sail, ready-made in TB Polibox (FR-DIN 4102)is composed of 100% PES, it weighs190g/m2 and has a width of157/235cm. It is constructed bywarp yarns 330 dtex–24threads/cm and weft yarns 330dtex-20 threads/cm; moreover, thefinish is applied by coating it in twophases with PU flameproof resins,

with hydro and oleo-repellent“Teflon” treatment and it has a lightsolidity 5/6, depending on thecolour of fabric. Membrane isarticulated on a plan that is inclinedwith respect to the rectangular planof the room. The sail is anchored inhigh points through cables thatstart from four points, which are intension by rolled up cables at thecapitals of the columns thatsurround the room; low points,instead, are tensioned by cablesthat are anchored in the four cornerpoints of the square floor where theceremony takes place. Furthermore,at the low points of anchorage fourlights are located, which worktogether in order to light up the sailfrom bottom up, and diffuseuniformly the light in the room,thanks to clear and reflectingsurface of the membrane. The sailhas a perimeter of 2,75m by 2,75m;it is based on a square plan witheight points of anchorage, four high

points and four low points. Thedifficulty of assembly andrealization, in this case, was solvingthe problem of anchorage for thetenso-structure without interveningin the pre-existent structures, so itwas tried to use elements likesupports without leaving any tracesafter dismantling. The choice of thesolution was a system of cables,which were rolled up on columnsthat surround the room, at theheight of the capitals, so it waspossible to have a correct

configuration of the sail and in thesame time it was possible to hidethe view of anchorages.

The sail dominates and shows thearea for prize-giving, in this way itgives to the platform an evocativeimage because of the reference tolightness of flight: a symbolicpresence linked to the mostimportant moment ofmanifestation, that is the prize-giving to the person who hada recognition for own devotion towork. The fabric does not only exaltvisually a physical space but alsocelebrates a meaningful moment(Figure 5).

The work for the installation“Impresa Donna” was designed in2004 and it was thought like asculpture of light, that had thefunction of exhibitor for picturesand documents which are collectedfor the exhibition about “Womenin Commerce” in Italy. Objects inthe exhibition are protected by asingular up-side down umbrella,realized with a translucence fabric,from which a set of cables starts inorder to connect symbolically theexhibition about contemporarycommerce with past commerce,located at a higher level of theexhibition room. The architecturalelement becomes an innovativesign that sets well in an evocativearchitectural frame with animportant historical and artisticvalue (Figure 4). The fitting-out hasdifferent functions, like functional,scenographic and symbolic one.The functional element resultsfrom an indirect lighting systemthat is provided on the membrane,so the membrane becomes anenlightening surface for exhibition

planes below; in fact some lightsare provided below the openumbrella, and one is located uponthe umbrella with coloured lightthat spreads softly in the room.Moreover, in order to avoid theproblem of light dispersion comingfrom down and in order to avoidhaving excessive light in the room,that could obstructs the visualperspective of space, a “lamp-shade” was designed, that is atextile doubly curved surface whichinserts itself on the up-side downumbrella and it completes the lightsculpture. The artificial lightingsystem underlines the global imageof the fitting-out and the historicallexicon of the central room inPalace of Exchange. Really, the lightis transmitted to the exhibitionplans below and in the same time itis diffused in the surrounding spacein order to exalt the historical andartistic context where the

exposition is taking place. Circular and up-side down the bigumbrella evokes image of a flower,which becomes a scenographic

element: a wide polygonal base forexhibition, from which the big

Name of the project: Prize-giving 25° CCIAALocation address: Central room of Palazzo della Borsa, Bovio Square, Naples, ItalyClient (investor): Camera di Commercio NaplesFunction of building: Expositive hallType of application of the membrane: Umbrella structureYear of construction: 2 0 0 2Architects: Aldo Capasso Structural engineers: Baku Group, NapelsManufacture and installation: Salvatore Sessa, NapelsMaterial: TB Polibox (FR-DIN 4102)Covered surface: 7,56m2

Cost: 1000€

Figure 5. Sketch for the installation duringPrize-giving 25° CCIAA, Palazzo della Borsa

INSTALLATION FOR PRIZE-GIVING 25° CCIAAPalazzo della Borsa, Naples

INSTALLATION “Impresa Donna”, Palazzo della Borsa, Naples

Name of the project: Impresa DonnaLocation address: Central room of Palazzo della Borsa, Bovio Square, Naples, ItalyClient (investor): Camera di Commercio NaplesFunction of building: Convention hallType of application of the membrane: Sail tenso-structureYear of construction: 2004Architects: Aldo Capasso Structural engineers: Baku Group, NapelsManufacture and installation: Salvatore Sessa, NapelsMaterial: TB Polibox (FR-DIN 4102)Covered surface: 19,6m2

Cost: 1000€ (Umbrella is property of artisan who realized it)

Figure 4. Sketch for the installation of ImpresaDonna, Palazzo della Borsa


umbrella rises and opens,together with a bundle of threadsthat starts from lower and risesup until to exhibition elements onthe higher level, involving andinvading entirely the room. Inconclusion, the symbolic value isgiven by a figurative choice of ablossom flower, aiming atevocating life and beauty, fromwhich a shy and pride past(historical undertakings) throwsan aware present (contemporaryundertaking), through the idealthread of doing and growth,represented by the cone ofthreads and light that connectsthe two exhibition points, locatedon different levels. In this case the membranechosen is the same fabric as in the installation for the prize-giving manifestation (see below),called TB Polibox (FR-DIN4102), that is ready-made by

sewing and it is realized as aretractable umbrella: in fact, it is easily closable when the exhibition for which itworks is over. The work is anautonomous structure in relationwith the architecture where it isplaced, in fact it doesn’t needperimetric anchorages to walls orpunctual anchorages to theceiling or floor, this fact alsoavoids problems when anchorageat pre-existent structure isprohibited. The construction of the fitting-out was done by a local smallhandicraft company: the installation was realized by anartisan who makes up umbrellas,by using sixteen bars inaluminium that run on a centralmast, like a big umbrella that canopen and close, and moreover itcan be totally disassembled andreused in other place.

CONCLUSION

Membranes become protagonist thanks to many qualities andfeatures that make possible a correct functionality for differentarchitectonic spaces and they can give a particular meaning toplaces where they are installed. From the works we havedescribed here, we can derive some considerations aboutpeculiar aspects of textiles, in particular about their adaptabilityand their facility to furnish, as well as their reversibility. So wecan say that membranes are very easy to adapt to differentspaces and in the same time they are able to modify thesespaces because of given needs, for instance expanding orrestricting delimited spaces, in height or in depth. Moreover,membranes can be included with lightness in contexts that areyet full of values and strong signs, without any volumetricinvasion in consolidated spaces; furthermore, membranes areeasily usable so they make places recognizable and perceptiblein a direct way, avoiding disorientation like it could happen inplaces which are not well designed. In conclusion, it’s possible tostate another and not less important reflection about therealisation cost of these installations: they are realised and constructed by local artisans, moreoverthey didn’t request excessive costs and long time forconstruction, also because generally membranes lendthemselves to different kinds of work or adaptation, in fact theyoften provide different solutions to practical problems thatfrequently occur on the building site and which must be solvedeven in phase of realisation.

� Paola Campanella, PHD student Università di Napoli Federico II

� [email protected]� Pictures of “Vesuvio Libri” are published here.

For pictures of other works, realized in Palazzo della Borsa, please contact the author.

New Tent ArchitecturePhilip Drew

Interest in tensile structures is fast growingthanks to ecological concerns and the newpossibilities offered by cutting-edge materials

and technologies. Tents have been prized for centuries for theirlightness, mobility, small footprint and structural elegance. Newtents offer innovative and significant solutions to age-oldproblems. With the demand on architects to touch the earthlightly, together with a cross-disciplinary interest in technotextiles,membrane structures are assuming new prominence and pleasingforms. This wide-ranging international survey looks at the exciting

possibilities of contemporary tensile building and the most interestingmembrane structures created in recent years. Includes: Architectural andcultural history of the tent; thirty recent projects grouped by theme, such asatrium covers and fabric walls, ring roofs and convertibles, small peaks, largewaves and accessible text descriptions, photographs and line drawings.

■ English ■ 27.0 x 24.4 x 2.7 cm, 250 illustrations in colour& black and white, 208 pages ■ Thames & Hudson Ltd

■ ■ ■

www.thameshudson. co.uk ■

ETFETechnology and Design

Annette LeCuyer

ETFE foil has recently become an important material for thecladding of technologically sophisticated and innovativebuildings. This material is very thin and lightweight and,when used in air-filled cushion assemblies, has enormous

strength and a range of adaptive environmental attributes. ETFE cushionenclosures became widely known primarily through Grimshaw Architects’Eden Project and Herzog & de Meuron’s Allianz Arena, and they are being usedon the spectacular swimming stadium for the 2008 Olympic Games in Beijing,the largest ETFE building envelope in the world so far. This book is conceivedas an in-depth introduction to the characteristics of ETFE and its applicationsin construction. Project examples explore in detail the specific characteristicsof ETFE building skins in the areas of structural behavior, light transmission,insulation, acoustics, fire engineering and environmental modification.

■ English ■ 230.4 x 23.5 x 2.3 cm, 397 illustrations, 246 incolor, 160 pages ■ Birkhauser ■

■ www.springer.com/birkhauser ■

Kengo KumaBreathing ArchitectureCreative Resources for Shade, Signage andShelter

Volker Fischer, Ulrich Schneider

The teahouse of the Museum of Applied Arts FrankfurtKengo Kuma's Teahouse is a masterly reinterpretation of a classical Japanesebuilding type. Delivered in August 2007 for the Park of the FrankfurtMuseum of Applied Arts (a Richard Meier Building), Kuma's innovativestructure in flexible, semi-transparent, 'breathing' Tenara-Membrane -inflated by means of a pneumatic system to a blossom like form - houses inthe interior the classical elements for Japanese tea ceremony. IntegratedLED technology allows the use of the teahouse at night; the interior can beheated by way of the membrane. The monograph, including an original textby Kuma himself, gives an in-depth documentation of this lyrical temporarystructure – an outstanding example of ephemeral architecture, combiningpoetry and technology - with many unpublished sketches, technical plansand with splendid colour photographs.

■ English, German ■ 188 illustrations, 126 in colour, 131 pages■ Birkhauser Boston ■

■ www.birkhauser.com

LITE

RATU

RE


Steel structureThe supporting structure for thetensile members is built in steel,except the foundation, obviouslybuilt in concrete. The elements thatconstitute the steel structure are:two main arches, ten diaphragmsbetween them, ten ribs with itssupports avoiding buckling in thearches, eight masts and a V-beam,and the slender beams that bracethe ribs (Figure 1).

ArchesThe pair of arches, with concreteabutments, span 64m with a sag of16m, which means a sag/span ratioof 1/4. At the highest points themaximum transversal spanbetween the arches is materialized,being a distance of 22m. The archeshave been designed as a paraboliccurve, which is an approximationfor the reversed funicular shape.Both arches, internal and externalhave a hollow box section with aheight of 600mm and a width of700mm, with a thickness of 10mmand 12mm respectively. The shapeof the arches is very interestingbecause the external faces show asingular play of light and shadowswhile the internal face is plane to

simplify the steel connections. Theslender diaphragms, with a squaresection of 200mm, have beenarranged between the arches toavoid the buckling of the archesand to support the compressivestrength due to the tensioning ofthe tensile membrane.Thanks to the lightness of thearches they could be built bymeans of a crane and auxiliary steeltowers acting as a temporarysupport (Figure 2).

RibsAnother interesting part of thestructural frame that supports thetensile membranes are the ribs.They have a parabolic semi arccurve, they span between 21m and32m and brace laterally the moststressed arch, being the inner arch.The ribs avoid fundamentally thelateral buckling of the arch, and in aminor way, the buckling in its ownplane, due to the flexural stiffnessof the ribs. The buckling safety isnot the dimensioning criterion forthe arch. The external arch isbraced to the inner one thanks tothe diaphragms, although theexternal arch is less stressed thanthe inner one.

The ribs have a hollow box shape,with the upper flanges adjusted tothe curvature of the textile which isattached to the ribs. These ribshave a width of 200mm and aheight of about 600mm, withseveral sheet thicknessesdepending on the span.The boundary ribs are veryimportant, because they have tocarry the unbalanced forces due tothe stand membrane. That is thereason for introducing the bracingbeams among the ribs. Thesebracing beams increase the safetyfactor of the ribs against lateralbuckling (Figure 3).

MastThe steel frame is completed withthe masts, being a fixing point forthe semi conical membranes. In thecrown of the mast a connectionsystem for the textile membranewith screwed bars was designed.These bars make it possible toadjust the tension in themembrane. The masts are 8m highand have a variable cross section,with convex flanges and concavewebs having a maximum width andheight of 250mm and 500mmrespectively, at the fixing to the

concrete frames of the stands(Figure 4).

Foundation for the main archesFinally, the membrane supportingstructure is completed by thefoundation of the arches,consisting of a surface foundationof 5m width, 8m length and 1.3mdepth and a wall of concrete of8.60m height placed on thefooting. This solution was neededdue to the presence of a servicegallery between the exhibition pooland the training and medical pools.The level of the gallery was 8.60mbelow the surface, being the reasonfor having used a concrete wall forthe foundation of the arches.Arising from the surface level, aprismatic concrete piece wasdesigned having a full formalcoherence with the section at thejunction of the arches. As conclusion, we can say that thisconcrete basement makes that theunion between the inner andexternal arch takes place 2.23mabove ground level, permitting asuitable free vertical span forpedestrian flows, the piece having ahuman scale indeed (Figure 5).

COMERCIAL MARITIMA L&Z

Tensile roof Orca Ocean ShowPuerto de la Cruz, Tenerife Island, Spain

Loro Parque is one of the biggesttourist attractions of the CanaryIslands. They had the ambitious ideato show the first orca spectacle inSpain. For that purpose Loro Parquedesired to have an impressiveexhibition site, in accordance withthe importance of the show. In thisway, Loro Parque asked for a roofdesign to cover the orcas’ swimmingexhibition pools. ComercialMarítima, as Contractor, and Arenas& Asociados, as Design Engineers,submitted the winning design. Thedesign criteria specified by LoroParque were fully met by Comercial

Marítima and Arenas & Asociados’ design. Loro Parque asked for a roof, comfortable for the spectators - protectingthem from rain, wind and excessive sun - and functional for the orcas - meaning that the roof was not a barrier incase the orcas had to be evacuated for medical reasons. The roof design pleased the owners, not only because itsatisfied their requirements, but it gave a fantastic view to the ocean horizon. It is important to add that the designof the roof was restrained by the fact that the foundations and the stands had already been designed. But this wasnot an obstacle for reaching a good design!

ARENAS & ASSOCIADOS

Tensile structureThe tensile structure made withpolyester PVC coated membraneFluotop 1302 by Ferrari is theprincipal material of the roof. It hastwo differentiated parts. One partcovers the Stand and the othercovers the Exhibition pool. Bothmembranes were tensioned fromthe boundaries by means oftractels (Figure 6).

The Stand MembraneThe Stand Membrane protects thespectators from the environmentalhazards, like sun, rain and wind.This membrane is anticlastic,organized in a succession of ridgesand valleys, with nine semi conicalshaped membranes in thebackstage of the Stand.This membrane is subdivided innine modules, each module beingsituated between two ribs of thesteel frame. The modules areconnected to the steel structure bymeans of spectra strands fixed toreeds at the ribs, clamps at theinner arch and bolts at the masts.All junction details weremeticulously studied to avoid thefiltering through of rain water in theexhibition pool, because this couldinfect the Orcas (Figure 7).In order to avoid the introduction ofunbalanced forces in the ribs, thetensioning of the Stand membraneswas carried out in several phasesand coordinated with thetensioning of the nearest modules.The textile Stand membrane wasnot only studied in a structural way.Throughout the design process wewere always looking for the bestaesthetical impression of themembrane covering, even whenthinking on the details, like theseams for patterning. The conicalshaped part of each Standmembrane module improves thestructural response against externaland internal loads due to its doubleanticlastic curvature in both ways,reducing the stresses in themembranes and the deformationsof such membranes.


Figure 1. Steel structure.Figure 2. View during the

installation of the arches.Figure 3. View during the assembly

of the ribs.Figure 4.Masts used as fixing points

for the semi conical membranes.Figure 5. Foundation wall and

concrete piece.Figure 6. Roof view.

Figure 7. Junction details.

Name of the project: Tensile Roof for Orca Ocean ShowLocation address: Puerto de la Cruz, Tenerife Island, SpainClient: Loro Parque S.A.Function of building: Covering for spectators and for

the orcas’ swimming exhibition poolsType of application : Protection against environmental hazards of the membrane and light transmissionYear of construction: 2006Architectural Design: Arenas & Asociados (Engineering Studio)

Comercial Marítima L&Z (Contractor)Project Manager: José Luis Olcina Structural Engineers and Consulting Guillermo Capellán/Santiago GuerraEngineer for the membrane: Arenas & AsociadosMembrane Structure engineering: Comercial Marítima L&ZContractor for the membrane: Comercial Marítima L&ZSupplier of the membrane material: FerrariManufacture and Installation: Comercial Marítima L&ZMaterials: Steel: 116000kg

Precontraint 1302T2 back PVDF 6010m2

ETFE of 200 μm thickness 75m2

Covered surface: 6085m2

Ratio: steel weight/covered surface 19 kg/m2

1 4

5

5 5

3

6

7

7

7

2 4

External Arc Internal Arc V-Beam

Bracing-BeamRib

Diaphragm

Masts

The Exhibition Pool MembraneThe Exhibition Pool Membrane is the mostattractive, from our point of view, part ofthe roof. We understand this membrane inconjunction with the arches, give fantasticsights to spectators.Covering 1600m2, this membraneintroduces an innovation in membranes andit is the conjunction of PVC and ETFEmembranes. The introduction of a centralband of skylights made of ETFE single layercreates an interesting play of light andshadows over the exhibition pool (Figure 8).The membrane was built in one piece at theComercial Marítima L&Z Factory. As it wasdone in the Stand membrane modules, theseams order was identically studied to reachthe impressive sight that spectators canreceive from their seats in the stand. Oncethe Exhibition Pool membrane wasmanufactured it was delivered by ship fromVigo to Tenerife, and then raised by meansof cranes to its position between the steelarches. The lightness of the membranepermitted to build the entire exhibition roofin one time. If another material would havebeen used, the construction phases wouldhave increased with it’s consequently delayin time. Construction time was a premise

imposed by the Property, Loro Parque, andone of the reasons of choosing a membraneroof was precisely the fastness that thebuilding of a membrane solution couldprovide. The rising of the membrane wasmade using first of all cranes and thentractels. The tractels achieve the slowestapproximation to the arches, permitting toadjust the union with the arches in severalphases. With this procedure the bigmembrane of 1600m2 could be installedwith the desired geometry (Figure 9).As it was told previously, one of theinnovating and interesting aspects of theroof is the conjunction of PVC and ETFEmembranes. The ETFE membrane, with athickness of 200μm, has a different Young’smodulus from the polyester PVC coatedmembranes. For maintaining compatibilitybetween the deformations of bothmaterials, steel cables were introduced overthe ETFE skylights. These cables were fixedto the connecting steel frame between thepolyester PVC coated membrane and theETFE foil (Figure 10). But not only were thesteel cables needed for achieving the highstress flow between the lateral sides of themembranes, it was necessary to reinforcethe narrow corridors connecting both sidesof the membrane. Summarizing, the narrowcorridors between the two sides of themembrane are high stress concentrationpoints, solved by means of steel cables andmembrane reinforcements.The connection of the membrane to thesteel arches was made using clamps, like itcould be seen in the Stand membranes.

ConclusionComercial Marítima L&Z and Arenas &Asociados have projected and built animpressive roof that has fully satisfied theProperty, Loro Parque, and that is enjoyedby the thousands of spectators visitingevery day the Orca Ocean Show. A mixingof technology and beauty for an unequalenvironment and exceptional animals, likeare Tenerife Island and the Orcas,respectively.

� José María Lastra� [email protected]� www.arquitextil.net� Guillermo Capellán Miguel� [email protected]� www.arenasing.com


ARTICLE

In architecture, the facade is oftenrecognised as a second skin or envelope.

No other building material matches thesecriteria better than foils and membranes

because of their fascinating, thin, light andtranslucent/ transparent properties.

In the last years the popularity especially of pneumatic structures has risen enormously. A new architectural accent wascreated with projects like “Allianz Arena” inMunich or “Watercube” in Peking. TensionedETFE (ethylenetetrafluorethylene) façades orroofs were composed of mainly single, small-size elements. Although hardly any of theseelements were identical, a tendency towardsthe use of standardised frame-modules can beobserved.

First prototypeof a foil façade of equal frame

modules covered with mechanically

pre-stressed foil.

Figure 8.The Exhibition Pool Membrane – conjunction of PVC and ETFE membranes.

Figure 9. View during the rising of the Exhibition Pool Membrane.

Figure 10. Detail conjunction of PVC and ETFE membranes.

8

9

10


Other than the mentioned pneumatic cushionmodules, there are also mechanically tensionedfoil frames. They are created out of a single foillayer tensioned and than fixed to a rigid frame.The spatial curvature necessary to stabilise thefoil can be achieved in different ways. Oneexample is using arches fixed within the frame. Awide range of shapes and design of the foilstructures can thus be created, varying fromarch, or high-point supported structures tohypar-surfaces or just flat tensioned framemodules. The first prototype of a foil façade, composed ofequal frame modules covered with mechanicallypre-stressed foil was installed in the TrainingCentre for the Bavarian mountain rescue divisionat Bad Tölz in Germany. In the commercialdistrict of the town, a simple rectangularbuilding was erected to provide a covered spacefor rescue training. Even helicopters were placedinside the building to simulate realistic rescueoperations.

The building was designed by the architectsHerzog + Partner from Munich. Its simple box-shape is accented by the arch-supported framemodules of the façade where the spatial curvedand tensioned foil is reflecting the light in anunusual way, sometimes allowing an insight,sometimes mirroring the outside landscape. Thefaçade is transferred into a three dimensionalstructure characterised by its high plasticity andvisual depth.The engineering, fabrication and installation ofthe façade were undertaken by Hightex GmbHfrom Rimsting in Germany. The modules weredeveloped, tested and optimised for their use asa single layer façade. The basis of the framestructure is a Z shaped steel section. The upper web of the section supports the foilwhich, after tensioning, is folded around thesection and connected on the diagonal web byclamp bars. Afterwards the arched is pressed into the foil tocurve its surface spatially. The arch is secured by

screws to a steel block, which inturn is fixed to the inner side ofthe frame section. The lowerweb of the frame is connectedto the steel substructure usingstandard bolts.This technique forms a singlelayered façade which protectsthe inside of the building from

wind and rain. For this application heat oracoustical protection was not required, theintention was actually to create realistic outdoorconditions as far as possible. Supported by theDeutsche Bundesstiftung Umwelt (DBU), one ofEurope's largest foundations to promoteinnovative environmental projects, a researchproject in cooperation with Hightex GmbH andHerzogdesign® has started to develop thesetensioned foil structures further. The aim is toextend the capacity of this technology towardsmultilayered, insulating and wide-spanstructures for extended roof and façadeapplications and to standardise these foilconstructions for future usages.

� Dr.-Ing. Gregor Grunwald� [email protected]� www.hightexworld.com� © Photo: Dr.-Ing. Gregor Grunwald

Name of the project: Training Centre for the Bavarian Mountain RescueLocation address: Bad Tölz, GermanyClient (investor): Bergwacht BayernFunction of building: Training CentreType of application of the membrane: ETFEYear of construction: 2008Architects: Herzog + Partner BDA, München / Prof. Thomas HerzogStructural engineers: Sailer Stepan und Partner Beratende Ingenieure für Bauwesen GmbH, MünchenProject Engineer: Johannes MaierConstruction management: Buchner, Wehbe & Partner, Bad TölzFaçade Engineering, Fabrication, Installation: Hightex GmbH, Rimsting

ETFE Façade Training Centre for the Bavarian Mountain Rescue, Bad Tölz, Germany


RESEARCH

IntroductionFabric reinforced membranes are a class oflightweight materials which are important formany different engineering branches like civil,aeronautical or marine engineering. They canbe used to efficiently cover big areas or encloselarge volumes with a minimum of structuralweight. Applications as membrane roofs,airship skins or sail materials demonstrate theircapabilities. The vastly expanding numbers ofarchitectural applications underline theaesthetic value of these types of lightweightstructures. Constructed as a composite of afabric embedded in or coated with matrixmaterial, they combine the load carryingcapabilities of fabrics with the functional tasksof the coating in order to obtain strong fluid- orgas-tight materials. Due to the microstructureof the fabrics, which consists of crossing groupsof yarns, the macroscopic deformation andfailure behaviour of fabric reinforcedmembranes differs strongly from the behaviourobserved in common homogeneous membranematerials. The interactions of the yarn groupslead to a non-linear deformation behaviour likecrimp interchange or shear locking and causethe discrete nature of the failure process, whichis characterised by a successive or collectivetearing of the single yarns.

The modelling approaches frequently used forthe design and dimensioning of membranestructures do not or only partially considerthese effects, as the numerical cost of theanalyses would drastically increase. In additiona more detailed description of the materialwould require also a deeper knowledge of thematerial at hand, which is costly andimpractical for realistic engineeringapplications underlying strict cost and timeconstraints. This lack of accuracy on theanalysis side is usually counterbalanced by theexperience of the engineers and the applicationof testing and a trial and error type ofapproach. Nevertheless, if confronted withcases in which failure occurs, in the civilengineering application usually in the erectionand pre-stressing process, numerical modelsusing the limited homogeneous materialrepresentation could not at allhelp further in explaining oravoiding the damage. The sameneed for high accuracy strengthpredictions is evident in aerospace

applications in which the material capabilitiesmust be fully exploited in order to allowminimum weight configurations. In this sense itis even more surprising, that modelling offailure in fabric reinforced membranes didgather only little attention in engineeringscience in the last decades. The present papershows some of the results obtained in a PhDthesis which aimed at contributing to thistopic. The thesis resulted from the authorswork at the Institute of Static and Dynamic ofAerospace structures of the University ofStuttgart under the supervision of Prof. Dr.-Ing.habil. Bernd Kröplin [1].

Yarn based modelling approachThe fabric membranes are characterised by amicrostructure of yarns, which are interwovenand embedded in a matrix material. Even if thefocus of interest is laid only on the macroscopicresponse of this kind of material, as it is thecase for engineering analyses of membraneconstructions, the underlying structure of yarnshave a dominating effect on the deformationbehaviour. The well known macroscopicnonlinearities in the fabric deformation namelycrimp interchange and shear locking, directlyresult from effects on the microstructure. Themajority of the existing modelling approachesfor fabric membranes cannot fully integratethis micro-structural influence in a simulationon structural level. The representation of thefabric as a continuum, as applied in finiteelement simulations, can include the nonlinearmaterial behaviour stemming from the yarnstructure, but its deformations and interactionsare not considered. In addition it has to beconcluded from theoretical studies on the unitcell of a fabric weave that the system responseis in reality load path dependent and not in anycase invertible. None of the commoncontinuum type approaches will be able toreproduce this behaviour. Instead it couldprovocatively be stated, that a fabric shouldrather be treated as astructure than asa material.

Simplifications of continuum type materialmodel approaches of course have their right toexist and will be the approach of choice for themajority of applications. Still it should be clear,that their accuracy and physical meaning isrestricted and has to be treated with great care.

In the work presented here a different route tothe modelling of fabric material behaviour ischosen. The starting point is the abovestatement, that fabrics should be treated as astructure. A discrete model for fabrics andfabric membranes is developed, which is basedon the microstructure level of the yarns. Theaim is not only to prove the fundamentalassumption, that the nonlinear deformationbehaviour as well as the failure process isdominated by the yarns. It is also sought toexplore, how far into the macroscopic world ofreal life structures this kind of bottom upmodelling approach can be driven. The usedabstract representation of the yarn structureapplies the well-known and provensimplification of linearised yarn paths betweenthe crossing points. A multitude of thisgenerated unit cells - the smallest repeatablestructure unit of the fabric - are assembled tobuild a macroscopic patch of fabric (Figure 1). In order to solve this system, an efficientnumerical method is necessary, allowing forlarge deformations, damage and freemovement. With the Discrete Element Method(DEM) an explicit particle based method ischosen, which is usually applied in granularmaterial modelling or in damage simulations [2].The result is a model for fabric membraneswhich allows a direct microstructurerepresentation in simulations on a structural(macroscopic) level. The macroscopicnonlinearities that stem from the interactionsof the yarns implicitly arise from therepresentation of the yarn structure withoutthe need for further assumptions.

Failure of fabric reinforced A yarn based modelling approach

Figure 1: Model representation of fabric material: fabric patch – unit cell –model unit cell – assembled model fabric patch.


RESEARCH

Fabric Membrane modelThe application of the Discrete ElementMethods makes it necessary to discretize themass of the fabric into point masses and todefine interactions between these mass pointswhich represent the mechanical behaviour ofthe constituents on this microscopic level. Theyarns are discretized into point masses locatedat the crossing points of the yarns (Figure 2).Three interaction types define the deformationbehaviour of the fabric: (A) longitudinal yarnstretching, (B) transverse yarn compression and(C) yarn rotation around the crossings. Twoadditional types of interactions, (D) matrixstretching and (E) matrix shearing, are appliedin order to represent the coating of a fabricmembrane. The simplifying assumption ofpiecewise linear yarn sections between thecross points is a common approach for thedescription of fabric unit cell followed e.g. by Kawabata [3].

Figure 2: Model representation of fabric membrane:Interactions for fabric (left) and coating (right).

In the frame of this model a relativetranslational movement of the yarns at thecrossings is inhibited (pin-joint-model), thusfriction effects between the yarns areneglected. Detailed descriptions of the modeldevelopment and the applied interactions canbe found in [1, 4 and 5].

Deformation mechanismsIn the frame of the authors work [1, 4 and 5]

experimental results for the deformationbehaviour of different fabric membranematerials have been obtained, which span therange from a pure, uncoated fabric to a stifffabric reinforced membrane. These results havebeen used to develop and verify the presentedfabric membrane model. A procedure for the

parameter identification basedon tests has been formulated.As the focus of the presentpaper is the failure simulation,only one example for thenonlinear deformationbehaviour is given here.

More information can be obtained in the givenreferences. Both typical non-linear fabricdeformation mechanisms could be observed inthe setup of the bias extension test. On the one hand this test is basically a sheartest, showing clearly the shear lockingmechanism. In the centre of the long specimena nearly pure shear region exists. Ifthe shear limit is reached, theresistance against furtherelongation of thespecimenincreases andfinally also alongitudinalwrinkle occurs. Onthe other hand, alsoregions of tension alongthe yarns are existent near the clampingof the specimen, which show the crimpinterchange mechanism. Thus the biasextension test is a suitable setup for an overallreference case for the assessment of the modelperformance.A bias extension test has been performed on apure glass fabric and a glass fabric coated withsilicon. Based on experimental results from uni-and biaxial tension test the geometric andtensional model parameters have beenidentified. The shear parameters are fitted withthe results of the bias extension test. Figure 3 shows the comparison of theexperimental and the simulation results. Thedeformation behaviour as well as theresistance response for the fabric and themembrane are represented well.

Failure modellingThe above stated results demonstrate theapplicability and the relevance of the model forthe deformation behaviour. Not only the

macroscopic nonlinearities are captured, alsothe deformation and movement of the localmicrostructure, the individual yarns, arerepresented. Of course a detailed model on thisscale will hardly be applied efficiently onstructural scale. Its major application regime isthe failure modelling. The failure is characte rizedby local interactions of the yarns as well as bymacroscopic load redistribution mechanisms.The derived fabric membrane model with directyarn representation thus is predestined for thefailure simulation, as both scales are capturedwell, and still, through the application of anefficient numerical solution technique,

consi derable parts of a structure can besimulated. The extension of the model for thedamage simulation offers very interestingopportunities. As the yarn pieces between thecrossing points are modelled individually,strength values can be assigned to each ofthem (Figure 4). The solution technique allows the failure ofsingle yarn pieces and the resulting loaddistribution and microstructure rearrangementis very close to the real fabric behaviour. Inaddition, statistical failure models can beapplied. The strength values of the individualyarn pieces can take differing values. Theirmean and standard deviation can becontrolled, if a statistical distribution functionis used for the assignment of strengths. In thepresented model the two parameter Weibulldistribution is chosen. The possibilities openedby this approach are demonstrated in theapplication examples.

membranes.

Figure 3: Bias extension test onfabric and fabricmembrane:Comparison ofexperimental andsimulation results.

Left: Visualization ofdeformation and plot ofshear angle form simulation (top) and picture ofdeformed membranesample (bottom).

Right: Plot of resistanceforce vs. patch strain.

Figure 4: Assignment of strength values to individual yarn pieces


RESEARCH

Failure SimulationIn the damage process of fabric membranes two types of failure could be distinguished: Failure through rupture is defined by an abrupt and complete breaking of a previously undamaged sample. In the opposite, tearing failure is characterized by a gradually growing crack in a previously damaged material. Examples for both types are covered in the following.

Rupture strength

In the first example the rupture strength of auniaxially loaded fabric patch is considered in asimulation with the fabric membrane model.The influence of the variance of the distributionof the strength values is explored in this setup.A patch of 40 x 40 yarns is modelled as rigidlyclamped and uniaxially loaded along one yarndirection. As the individual strength values ofthe yarn pieces are randomly distributed(following a statistical distribution), a singlesimulation is not significant any more. A number of simulations have to be performedand statistically evaluated, in order to obtainmeaningful results. In the given examples, sixdistribution functions are considered with fiveruns each. The results of the 30 runs plus oneadditional run with equal strength values for allyarn pieces are given in Figure 5.

An increasing spread of the strength values,which is realized by a reduction of the shapeparameter α of the Weibull function

parameter, leads to a considerable reductionof the strength of the patch. The failureprocess changes from a rupture type with one single continuous crack in the case of lowspread to distributed cracking all over thepatch in case of a high spread of yarnstrength (Figure 6).

The failure regime in the latter case is larger, spanning over a considerable region of strain, while the maximum resistance islower than in the abrupt rupture case.The spread of the individual strengthvalues can be seen as an intrinsic materialparameter and is characteristic fordifferent material types. The distinctionbetween a brittle and a more plastic typefailure behaviour can be treated in thissense. The model allows the fitting of thedistribution parameters to the assumed orexperimentally obtained materialcharacteristic.

In the second example the tearing behaviour offabric membranes with different coatingstiffness is considered. A patch with an initialcrack is loaded uniaxially perpendicular to thepre-crack and along one fibre direction.Variations in the initial crack length are applied,measured in terms of the crack length to widthratio (Figure 7). Four combinations of materialparameters for the fabric are chosen in order tocover the range from the pure fabric over a softand medium to a stiff membrane. The spreadof the distribution function of the yarn strengths is fixed at a medium value of α=30.As result the maximum resistance force of thepatch is obtained. This value is divided by thenumber of initially load carrying yarns andmade dimensionless with the strength of theundamaged reference patch of same material.The plot in Figure 7 summarizes the simulationresults.

For the uncoated fabric, no influence of thecrack is obtained. With increasing stiffness ofthe coating, the resulting strength value isreduced. The observed reduction is also dependent from the length of the crack, but

nearly constant for crack lengths awayfrom the limits of total or no initial slits.The result is in a certain sense surprising.An increasing stiffness of a coatingreduces the efficiency of the load carryingcapability of the fabric membrane undertearing conditions. The mechanism that isresponsible for this effect can beexplained with the applied model: Thecoating of the fabric leads to a transfer ofload from the region behind the pre-crackinto the remaining yarns through anincreased shear stiffness. This leads to anadditional overloading of the next yarn atthe crack tip. This overload of the nextyarn is even higher, the stiffer the coating gets. In Figure 8 the loading situation prior tothe first yarn failure is visualized for thefour materials. The colour coderepresents the load of the individual yarnsin relation to its load limit. It gets clear,that the coated patches show a strongeroverload of the yarns at the crack tip andthus will result in a reduced utilization ofyarn strength in a tearing situation.

Figure 7: Uniaxial tearing with different membrane materials. Left: visualization of test setup with initial slit.Right: tearing strength as maximum resistance force per yarn divided by therupture strength of the considered patch vs. relative crack length.

Figure 5: Rupture of a uniaxially loaded patch.Left: visualization of setup. - Right: plot of force resistance per yarn vs.patch strain for five different cases of Weibull strength valuedistributions characterized by the shape parameter α .

Figure 6: Rupture of uniaxially loaded patch: crack pattern for strengthvalue distribution with low spread (left) and high spread (right).

Figure 8: Uniaxial tearing of fabric membrane: load situation around crack tipprior to first failure for the four different material parameter configurations.

Tearing strength


RESEARCH

In this last application example the previous tearing setup isextended to a biaxial load situation. A now quadratic patch isclamped at all four sides and loaded along both yarndirections with strain control. The ratio between the appliedexternal strains in the two directions is one, i.e. equal load isapplied. An initial crack is introduced in the patch which isinclined at 45 degrees to the two yarn directions (Figure 9). The interesting aspect in this setup is the direction of crackgrowth and the pattern of the final cracking. In order toreduce complexity, only one material system representing amedium stiff fabric membrane is considered.As a result of the simulation, the forces inthe two directions are obtained. Figure 10 shows the force vs. the appliedstrain in the two directions warp and fillon the left. In the given example the fillyarns reach their failure levels first. Theynearly completely fail before the crackingof the warp yarns starts. The visualizationsof two sequential cracking states on theright side of Figure 10 depict the damagestate after the failure of the fill yarns only (top) and at the end of thesimulation run, when both yarn groupsare broken (bottom). The order, in which the two groups break, isdepending on the specific distributedstrength values. In a second run with the same set of parameters but adifferent random collection of strengthvalues, this situation might as well prefer the warp direction. The loading situation in the patch isdepicted in Figure 11. The strain of the individual yarns dividedby their strain limit is colour coded forthe warp yarns in the top and for the fillyarns in the bottom row. From left to right the figures show the situation before the first yarn failure, after complete failure of the fillyarns and after the final failure of the warp yarns. As in the case of the uniaxial tearing, the nextyarn to the crack tip is overloaded in comparison to the yarns further away from the crack tip. It isnoticeable, that the already fully developed crack in the fill direction has only a small influence onthe strain situation in the second direction. Thus two major observations could be made in this simulation: 1) The fabric membrane shows a clear tendency to break parallel to the yarn directions. 2) The two yarn directions break nearly independent from each other. The first issue is an observation made also in experimental studies on the biaxial tearing of fabricmembranes. The second observation is also depending on the stiffness of the coating. The moreload is carried by the coating the higher the interaction of the failure in the two yarn groups gets.Both aspects could not be obtained within a continuum type material representation and showclearly the advantages of a modelling approach for fabric membranes based on the directrepresentation of the yarns.

CONCLUSIONThe obtained model makes use of thefull capabilities of the approach with adirect microstructure representation. Itenables an integration of the theoreticalmodels for the statistical damagedescription into a simulation on astructural level. Furthermore it iscapable to reproduce in a realisticmanner the tearing and rupture processof the fabric membranes. The developeddiscrete model for fabric reinforcedmembranes allows the exploration ofthe interactions of the yarns and theinfluence of the coating materials in thesimulation of experimental setups likethe uniaxial or biaxial tearing. Itsapplication can lead to a deeperunderstanding of the processes thatcharacterise the failure of fabricmembranes. The scale of consideredproblems is limited by the availablecomputer power. Currently applicationsto patches of few hundred yarns per sidehave been demonstrated successfully.Thus the model is ready for applicationon the level of test lab specimens. Asadditional final conclusion theuniqueness of the material behaviour offabric membranes should be againpointed out. There exist only few othermaterials in which the microstructurelength scale is as near to themacroscopic level as in the case offabrics. The nonlinearities in thedeformation behaviour and the specificfailure mechanism are directly related tothis close connection of structurallength scales. All given results showclearly, that considerable care has to betaken in the choice of simplifications toapply in modelling approaches for thisextremely interesting material class. Inmany cases the traditional engineeringapproaches basing on finite elementsimulation and continuumrepresentations will not yield sufficientaccuracy of analysis results.

� Dr.-Ing. D. Ballhause� [email protected]

REFERENCES[1] D. Ballhause; Diskrete Modellierung des Verformungs- und

Versagensverhaltens von Gewebemembranen (German), Dissertation, Universität Stuttgart, ISD, July 2007.

[2] N. Bicanic. Discrete Element Methods. In: E. Stein and R. de Borst and T.J.R. Hughes (Eds.). Encyclopedia of Computational Mechanics -Fundamentals, John Wiley and Sons, 2004.

[3] S. Kawabata, M. Niwa, H. Kawai. The finite-deformation theory of

plain-weave fabrics; Part I: The biaxial-deformation theory. Journal of the Textile Institute, Vol 64(2), pp.21–46, 1973.

[4] D. Ballhause, M. König, B. Kröplin; Modelling fabric-reinforced membraneswith the Discrete Element Method. In: E. Oñate, B. Kröplin (Eds.). Textile Composites and Inflatable Structures II, Springer, 2008.

[5] D. Ballhause, M. König and B. Kröplin; Modelling of woven fabrics with the Discrete Element Method; Computers, Materials and Continua, Vol. 4(1), pp21-30, 2006.

Biaxial tearing

Figure 11: Biaxial tearing:strain distribution in warp and fill yarns at different times.

Figure 10: Biaxial tearing. Left: resistance force vs. patch strain for warpand fill direction. Right: crack pattern after complete failure of fill yarns(top) and in final state after failure of warp yarns (bottom).

Figure 9: Biaxial tearing: visualization of testsetup with initial crack under 45 degrees to loadand yarn directions.

In October2008 workbegan on a newproject in theschool of CivilEngineering and Geo -sciencesentitled ‘A pragmaticapproach todetermining the mechanicalbehaviour ofstructural fabrics.’ Alison Jackson, a NewcastleUniversity Civil Engineering graduate with 2years industry experience at Arup is supportedby a supervisory team comprising Prof. PeterGosling, Dr. Ben Bridgens and Prof. Jon Mills(photogeometry and measurement) to carryout the 3 year study. The project is backed by aconsortium of industrial partners; ArchitenLandrell Associates, Arup, Buro Happold,Ferrari, Tensys and the UK Engineering andPhysical Sciences Research Council. NewcastleUniversity’s floating biaxial test frame (Figure 1)will be used in conjunction with a hinged frameshear accessory (Figure 2) in a new temperaturecontrolled test facility (Figure 3) to obtain dataon material behaviour under biaxial and shearloading. This data will be used to demonstratethe capabilities of a predictive numerical modeldeveloped within the project.The aim of the research project is to develop anumerical tool to enable the reasonableprediction (e.g. within a narrow range) of non-linear stiffness and strength characteristics ofcoated and uncoated woven fabrics which isappropriate for analysis of fabric structures. Thiswill be achieved in a number of steps, initiallyimproving the existing predictive unit cell model(Figure 4) proposed and partially developed byBridgens (PhD Newcastle 2005) to include, forexample, the use of non-linear yarn elements,non-linear crushing response, and the frictionaleffects at yarn spatial intersections.

The unit cell model will then be extended toinclude shear response which will require theintroduction of the concept of lock-up at angleas a function of biaxial stress ratio andmagnitudes. Repeated concatenation of unitcells will be used to produce a “patch of fabric”(e.g. 300 – 400mm) required for shearbehaviour prediction. The extended ‘patch’model will then be used to predict the strengthof the fabric under virgin and torn (e.g. 40mmtear in a 400mm wide patch) states byconsidering both stress and strain states.

The capabilities of the predictive model will bedemonstrable by comparison with dataacquired from a series of uniaxial, biaxial andshear tests. In order to run these tests a newprotocol will be written for shear and failuretesting of fabric based on the principles of theexisting biaxial test protocol. This will enable fullquantification of the fabric response to in-planeloads allowing extensive comparison betweentest data and predicted values. The variability infabric strength and stiffness characteristics willbe identified from physical testing and theability of the numerical model to predict thiswill be demonstrated. In order to do this thevariations in measured parameters will be inputinto the numeric model to predict the samemeasured variability of the parent fabric.Finally the predictive model will be linked tothe concept of info-gap theory and the

application of the predictive tool to explore theuncertainties in the existing analysis of fabricstructures. It is hoped that this will enablefuture design to maximise the robustness of thestructure for a given performance (e.g.stress/deflection etc.) where knowledge of thevariability of the fabric is incomplete. This willbe achieved by consideration of only simpleexamples (pseudo manually) as an early proofof concept in preparation for full adoption ofthe tool in a future project.

The key hypothesis is that the non-linearstiffness and strength characteristics of coatedand uncoated woven fabrics can be stated as anenvelope of values. Complex performance canbe predicted from simple information which iseasily obtainable from a small sample of thematerial in question when referenced against adatabase of predicted and test responses.Whilst the predicted envelope of values maynot be as accurate as that obtained from a fullset of comprehensive tests it is expected thatthe predicted behaviour will be suitable for allbut the most demanding projects and betterthan any obtained by current biaxial testing.

� Prof. Peter Gosling Newcastle University

� [email protected]� www.ceg.ncl.ac.uk


A pragmatic approach to determining the mechanical behaviour of structural fabrics.

Figure 1: Floating biaxial rig.Figure 2: Hinged frame shear

accessory.Figure 3: The new temperature

controlled test facility atNewcastle University.

Figure 4: Unit cell model developed by Bridgens.1

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INDUSTRY SUPPORTED PHDSTARTED AT NEWCASTLE UNIVERSITY

RESEARCH


Name of the project: “The Castle”Location address: Santa Pola, Alicante, SpainFunction of building: DiscothèqueType of application of the membrane: tensile surface structureYear of construction: 1980Architects, structural engineers and Donada, Llorens & consulting engineer for the membrane: SoldevilaContractor for the Membrane, Arquitectura Textil, manufacture and installation: Montmeló, SpainMembrane: PVC coated polyesterRoofed area: Ø 26m = 531m2

Circular textile roofs usuallyend up as conoids with acentral mast or suspended

high point. Nevertheless, othersolutions are possible provided thatthe perimeter is not included in thesame plane. For the “Castle” Disco inSanta Pola a circular paraboloid wasdesigned.

DescriptionThe enclosure is circular in plan, 35min diameter, including a centraldance/stage floor, surrounded by acircular porch with tables, benchesand seats. An intermediate space in-between provides eithercomplementary seats or a centraldance/stage floor extension. Mainentrance, services, bar and otherfacilities complete the wholescheme (Figure 1).

Textile roofsTextile roofs were envisaged for thecentral dance floor and theintermediate space.The central dance floor is roofedwith a concave double curvedsurface, stretched against a spatialring, 12m in diameter. The spatialring is made of two leaning trussedarches supported by 6 masts thatfollow and reinforce the contour ofthe dance floor or stage (Figure 2).The intermediate space, 26m indiameter, runs between the archesand the porch. It is divided into twosymmetrical parts by the drainage ofthe central roof. They are attachedto the perimeter independently insuch a way that either of both parts,only one or none can be installed forsun protection purposes. Theycomplete the space directing theshape towards the centre, assistedby the seams resulting from thecutting pattern. Notice that thecutting pattern is not only a concernfor making the form, but it alsocontributes significantly to the

perception of the surface, in thiscase, directed towards the centraldance or stage floor, emphasizingthat something (or somebody)important is going to happen there.

Steel structureThe steel structure is also relevant.There are 4 single CHS masts and 2 three-fold CHS masts supportingthe trussed arches. The porch isdelimited by a series of 20 doubleCHS in order to be self-supportingand avoid ties between tables andseats (Figure 3).

Design concernsThe design of the aforementionedroof was used to reveal the difficultyof most 3Ddesign programs to find insome circumstances the equilibriumform of a physical model of a tensilesurface structure. The figures showthe perimeter of the intermediatespaces, the surface generated by a3D design programme (Figure 4),a physical model (Figure 5) and acomputer form finding made withEasy Demo, Technet GmbH (Figure 6). Notice that the 3D designmodel is not in equilibrium and is not feasible.

� Josep Ignasi de Llorens Duran� [email protected]

L L O R E N S

A circular paraboloid The CastleDiscothèque, Santa Pola, Alicante, Spain

Figure 1.Plan and section.Figure 2. Roof above thecentral dancefloor or stage andabove the inter-mediate space.Figure 3. Steel structure.Figure 4. Surfacesgenerated by 3D designprogramme.Figure 5. Physical model.Figure 6.Computer formfinding made withEasy Demo.

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ESCRIG & SANCHEZ

Tensile fabric structures offer possibilities for the solution of urbanproblems which no other type of structure permits. In the Expo Zaragoza2008 site (Saragossa, Spain) a 400m long structure has been designed thathas turned out to be one of leading attractions of the event. It consists ofthirteen pieces of torical surfaces that twist and turn at a height of 17m,taking on the appearance of a river. Technically, it includes some advancesin structural geometry and artistically, it stands out due to its formaldecoration.With the aim of providing shade for the participants’ street we build apartial roof along the 500m of its length in such a way that no elementwould interfere with the views from the pavilions to the street or obstructthe route where various activities would take place. This commission would not have been a problem in itself if it were not forthe fact that several limitations existed. We could not place anchorages onthe existing buildings because they were not dimensioned for it or in thepublic walkway as activities which require the street to be obstacle-freewere foreseen. The structural and architectural solutions had to becompletely stable in themselves with respect to horizontal loadingbecause the pavilions could only provide vertical reactions. Theselimitations strongly conditioned the final design, which was arrived at bytwo different paths. The first was conceptual, and consisted in providingthe project with a symbolic image. The other was structural, via which wesearched for possible forms which would resolve their stresses internallyand would convert them exclusively into vertical loads. The conceptual idea consisted of using the exhibition's own leitmotiv,based on water, and building a river which flowed overhead and cast itsshade onto the main street. Our objective was to represent Zaragoza's river(Figure 1).

The structural idea was based on a self-stressed system which resolves allpre-stresses internally and only transmits to the exterior the actions of

gravity, snow and wind loads. We thought that a modular design wouldhelp in solving all the problems and modules of 32m x 24m were proposed,with a central part of these comprising 14m x 32m of textile. To preventthe repetition of 13 of these modules from being monotonous, they weremounted in such a way that they curve, as though it were the meanderingof a river bed (Figure 2).

In order to round off the idea, the textile roof is covered with artisticpatterns, which we consider to be a plastic work which combinestechnique and design, as can be seen in the pictures of the finished project.We wanted the architectural image to be complemented with a design byone of the country's most important artists, in this case Isidro Ferrer(Figure 3).

Our main challenge was to achieve a support for the textile fabric surfacescapable of functioning in a self-stress state, that is to say, with verticalreactions exclusively. The horizontal reactions typical of these kinds ofstructures and arches were avoided with a disposition as in Figure 4, wheretubular metallic arches would be stabilised by tendons on the upper part ofthe arches and by cables below them. It is precisely the introduction ofthese upper tendons which has been special for this project, since an arch isconsidered to be stable when it cannot open by an outward horizontalthrust, and here the arch cannot expand because of the lower cable, butwith respect of the action of the fabric we have also prevented it fromclosing inwards as it cannot increase its curvature due to the upper tendon.

The lower cable works with pushing loads and the superior tendons workwhen pulling loads are acting.

A succession of fourteen arches set at 32m intervals leaves thirteen zonesin which modular roofs can be drawn taut. The covers are designed to beseen and to be used as a continuous canopy over the street.

Textile riverover participants' street Expo Zaragoza 2008, Spain


The tensile fabric structures used are surfaces of toric geometry (the innerpart of a doughnut), 14m wide and 32m long, as mentioned above. Thepieces used are limited by two vertical planes and two curves with circularprojection.In order to support the curved fabric borders we placed curved steel cableedges at the exterior, which are the fundamentals of the entire structure,as between the self-stressed arches and these border cables or “bolt ropes”(curved edge cables with bolts, see Figure 16) a highly resistant fabric istensioned, which defines our overall design. In order to complete it we dispose another series of cables and rods whichare fundamental for the functioning of the assembly but which are barelyvisually perceptible.

The way the arches are supported along the axis is different on the rightand on the left side. On the right, they are connected to the roof of thepavilion buildings while, on the left, they are connected to the top of 17mhigh masts (Figure 5). These masts are of variable cross section and arepinned at their base so as to easily absorb the twisting and bendingmovements typical in these types of supports for light structures (Figure 6). Masts and arches are rigidly connected, more to facilitateconstruction than to transmit bending loads (Figure 7).

Horizontal stability of the masts is guaranteed by diagonal cables for thelongitudinal direction which prevent them from turning over, and with thearches in transverse direction (Figure 8).

On the roof, arches are supported directly on the post-tensioned concreteslab at the points where there is a concrete support directly below (Figure 9) or on a steel laminated rod to avoid encountering the heads ofthe tension cables of the concrete slabs (Figure 10). These supports aredimensioned to carry almost exclusively vertical loads and only some smalloccasional horizontal forces.

The arches tensioned on their lower side with a cable and on the upper sidewith a combination of sticks and tendons are constructed in a polygonalcurve made with segments of 400mm x 200mm rectangular pipes wherethe tensile fabric, interior cables and edge cable devices are connected to.Because the street is not uniform in width not all of the arches are equal.There are two types: arches with a 24m span and arches with a span of32m, although all of them have the same height of 6m (Figure 11).In order to make the edges of the textile taut a succession of parallel cableswas added and connected to a border comprising two parallel cables in aparabolic curve, resulting in a technological solution such as shown inFigure 12. Generally speaking, we try to make our designs completelystable in themselves, even when the textile elements are absent. In thisway, even if a textile cloth had a structural defect this would not imply thecollapse of the rigid elements.

Everything that has been said about a self-stressed system works for theinterior modules, but not in all aspects for those at the beginning and theend of the street. This is because there are horizontal forces here that canonly be absorbed by means of anchorages to fixed points with thetransmission of important horizontal components. In order to solve thisproblem of equilibrium we ran inclined cables to fixed points on thefoundations, as can be seen in Figure 13. We chose to connect at placeswhere there were already other types of supports so as not to increase thenumber of obstacles in the street. On the other hand, as the loads fromthese cables are tension forces, the performance of the foundations isimproved at the points where the walkways between pavilions aresupported.

The role of the roof is not exclusively functional - providing shade - but it is also an important part of the functioning of the structure. When we installed the textile modules we achieved a total equilibrium ofstresses where none of the elements is superfluous and each isindispensable. Nevertheless, certain considerations need to be taken intoaccount with this kind of architecture in tension, and are worthemphasising as design principles:

1. Despite its high resistance under tension, the textile has very littleresistance to tearing and rips can occur at the joints. When this happensstability is only lost between cables and the rest remains in place, andnormally in good condition.

2. The textile meshes are designed in such a way that they maintain self-equilibrium when the textile is not in place, that is to say, that the

Figure 1. First drawing of the idea. Figure 2. The aerial view.

Figure 3. Pattern created by Isidro Ferrer.Figure 4. The first module completely finished.Figure 5. The masts with variable cross section.

Figure 6. The hinge at the base of the masts. Figure 7. The top of the masts.

Figure 8. The complete structural system.Figure 9. A hinge on a slab on top of a building.

Figure 10. A hinge with distributed supports.Figure 11. The skyline view from the terrace.

Figure 12. Curved edge cables and connections between fabric and ropes.Figure 13. Anchorages at the ground foundations.

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Name of the project: Textile roof over the street of participants in the Expo 2008 Zaragoza

Location address: Zaragoza Client (investor): Sociedad Estatal EXPO2008Function of building: to shadowing a public space Type of application of the membrane: Roofs and Canopies Year of construction: 2008Architects: Felix Escrig and José Sánchez Graphics: Isidro Ferrer Multi disciplinary engineering: Performance S.L.Structural engineers: Performance S.L.Consulting engineer for the membrane: Performance S.L.Engineering of the controlling mechanism: Performance S.L.Main contractor: IASO S.A.Contractor for the membrane: IASO S.A.Supplier of the membrane material: Ferrari Manufacture and installation: IASO S.A.Material: FERRARI REF. 392Covered surface: 5000m²


absence of textile does not imply either the fall of cables or the collapseof rigid elements.

3. These types of modular structures have to keep functioning even in theabsence of a module, whether it is interior or exterior.

4. The stability of these structures is based on the fact that they are in astate of strong internal tension, which we refer to as pre-tension, beforestarting to introduce any exterior load.

5. The external loads, basically due to the wind, can act in a different wayon each element at each moment in time.

6. The wind loads concentrate their energy in gusts and are thus dynamicsof very long periods, between 0.5 and 2 seconds, which means that theirmovements are visible and therefore disturbing. The greater the initialpre-tension to stabilise the whole, the shorter will be the period ofvibration.

7. The forms that can work for this type of roofs are warped. This meansthat they cannot be constructed from flat surfaces except with anadequate cutting pattern. In our case, we opted for a cutting pattern of atransverse type which takes full advantage of the commercial reel width.

All these aspects have been taken into consideration in the constructionand structural composition of this roof.Along with those already shown in previous figures, Figures 14 and 15 showthe key aspects of the overall solution. Generally speaking, theconstruction details of this type of cover have been studied in depth andwe have turned to previously-known solutions, although a certain degreeof innovation is always necessary. Thus the “bolt ropes” (curved edgecables) are resolved with double cables in order to tighten the cables whichpull the textile taut (Figure 16) and the superior screw threads of the arches are resolved bit by bit by means of a nut at each end (Figure 17).

One of the most important aspects of a textile roof project is to programthe sequence of assembly and tensioning. In this case we chose to stressthe entire metallic mesh previously, apart from the stressing whichdepends on the existence of the textile. Then it was possible to mount andstress each module in turn, which greatly facilitated the constructionprocess. Moreover, it has been necessary to work in a space full ofobstacles, and without priority over other work in the street as far asassembly was concerned (Figures 18 and 19).

Once the assembly is completed it is necessary to proceed to introducetension into the fabric until achieving nominal design stress. This is difficultto check in the cables and even more so when it comes to the surfaces. The mechanised techniques which exist for this are not very trustworthyand it is better to operate by approximation on the basis of the reactionsas, in the absence of external loads, the overall result suggests anequilibrium which is easy to check. The force applied via the screw threadsat the extremes determine what happens in the interior in the absence ofwind. For this reason, if we check the reactions of the few anchoring cableswe have on the exterior we will be able to make an approximateestimation of what happens to the whole. The analysis of this structure is really quite complicated due to itsextension and owing to the nature of its components. Moreover, it isdifficult to evaluate the loads and the simultaneity of their action. It is forthis reason that we have made separate calculations for the textileelements and the metallic ones. In this way, the surfaces, along with theiredge elements, have been analysed using the SAP2000 programme inorder to obtain some generic stresses. The supporting elements,meanwhile, have been dimensioned with these previous reactions in orderto obtain some stresses and reactions which have served to dimension theentire structure. Without entering into further detail, the loads which havebeen taken into consideration are wind loads when the wind is blowing at100 km/h, and snow has not been taken into consideration as this roof willonly be used during the three months that Expo 2008 lasts.Posterior to the construction, wind speeds of up to 90 km/h have beenmeasured without appreciating any alterations in the structure, which hasserved as confirmation that it is an appropriate and successful design.

� Félix Escrig, José Sánchez and Mercedes PonceSchool of Architecture of the University of Seville

� [email protected]

REFERENCESEscrig, F. Sánchez, J. and Llorens, J.I. STAR Structural Architecture no. 5 and 6,

Universidad de Sevilla, 1996 ([email protected]). ISSN 1137-201XForster, B. Mollaert, M. “European Design Guide for Tensile Surface Structures.

Tensinet, 2004 Brussels ( [email protected]) ISBN 90 8086 871 x

Figure 14. Structuralelements at the top ofthe masts.

Figure 15. Structure atthe top of the slabs.

Figure 16. Border catenary.

Figure 17. Tension screwsof the tendons on thearches.

Figure 18 and 19. The process oferecting a module.

Figure 20. Aerial view of theoverall structure.

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The new Rhine-Neckar-Arena inSinsheim has been recently

completely finished.A stand roofing system made of technical textiles round off

the newly built stadium and offers protection for more than

30.000 spectators. CENO TEC GmbH, an enterprise

from Greven-Germany, producedand installed the roofing system

within only a few months.

High-tech materials for functional useA total area of 19.500m² is coveredby technical textiles. The amount ofmaterial used is around 60.000m².For optical and acoustic reasonsnot only the upper side, but alsothe lower side of the steelsupporting structure is coveredwith the membranes. Two differentmembranes were used, dependingon the function. The uppermembrane that faces the outside isintended to protect against theweather whilst at the same timeallowing light through onto thestands. 56 roof fields, each with 5support arches, are covered witharchitectural membranes made oftranslucent PVC-coated polyesterfabric (type III) having a dirt-repellent fluoropolymer coating.This varnish is more weathering resistant thantraditional varnishes. The lowermembrane that faces the stands is

intended to have an opticallycalming effect. A fine-meshed PVC-coated polyester screen fabric isused for this. A total of 750 steelframes are finished with semi-transparent material.Another special feature of theroofing system is the fact that the750 covered steel frames wereproduced in accordance with a jointmodel such that they can bedisplaced in order to achieve aclosed homogenous ceiling.

The architect's design has beenconsequently implemented with

many technical individual solutions. The roof edge glazing planned forthe inside of the stadium is alsopart of CENO TEC’s scope ofdelivery. Around 6.000m² ofpolycarbonate panelling willprovide for protection against theweather and translucence aroundthe entire circumference of theplaying field.

� Anne Bosse, CENO TEC, GmbH Textile Constructions

� [email protected]� www.ceno-tec.de � © Uwe Grün

General planning: agn Niederberghaus & Partner GmbH Membrane support structure planning: form TL Ingenieure

für Tragwerk und Leichtbau Structural steelwork planning: AHW Ingenieure GmbHArchitects: agn Niederberghaus & Partner GmbHMembrane construction manufacturer: CENO TEC GmbH (D)Design: Arched membrane / flat stretched lower membrane frameType of membrane: Coated polyester fabric with PVDF surface refinement

Floating RoofNew Rhine-Neckar-Arena, Sinsheim, Germany

C E N O T E C

Architen Landrell has inOctober 2008 completed thedesign, manufacture andinstallation of largest Tenarastructure in the UK for theopening of the WestfieldLondon Shopping Centre.Working closely with theWestfield designers andconstruction profes sionals,Architen Landrell were contracted to create a 16 bay fabric canopy tocover and protect the ‘Eat Street’ area of the new WSL white city project.The area, which houses the main restaurants, cafes and bars on the site, isone of the busiest streets within the complex and therefore it was impor -tant to the designers to provide weather protection but also to keep thelight and open air feeling. With Architen Landrell’s guidance, the teamchose to use Gore Tenara, a PTFE based fabric which offers 30% or 40%light transmission, and at 160m long it is the largest Tenara structure inthe UK!The canopy itself is split into three sections and is fixed three stories up,cantilevering off the main building. Due to the compressed programme towards the end of the Westfield 6year build, the street became excessively busy with other contractors. Asa result, we chose to perform the whole installation at night with multiplecranes and cheery pickers over a period of 2 months. Working nights alsohelped with access issues caused by the narrowness of the street itself.Cherry pickers and scissor lifts were adopted to take up minimal space butto speed up the installation process. The tight deadline was a realchallenge for the team and required hard work, dedication and attentiveproject management. However, the work was completed and theshopping centre opened on time to the delight of all involved!

Covering almost 1200m2,thirty seven 2 layer ETFE cushions form awinged canopy providingvisitors to the Westfield WhiteCity Shopping with weatherprotection and a stunningarchitectural feature. The ETFE cushions cover the60m bus interchange and

ensure maximum light is transmitted to the space below – creating a light,airy and ultimately safe-feeling environment. The ETFE foil, however, isnot 100% transparent. The two ply cushions have a standard 40% frittingto the top layer which minimizes glare and controls solar gain but stillallows plenty of natural light to permeate. The Architen Landrell team,when starting work on the interchange canopy, was presented with adesign concept which was developed alongside the clients engineer.Essentially a straightforward ETFE cushion canopy, this project gave theelectronics team a chance to develop and apply their in house controlsystem. The control system monitors and adjusts all aspects of theinflation system 24 hours a day/7 days a week and includes a remote diagnostic tool so it can be accessedfrom anywhere in the world. Using multiple sensors located throughoutthe structure, it automatically monitors the external environment andadjusts the pressure of the cushions accordingly. It also has an inbuiltdehumidifier which means the unit can anticipate snow by monitoring thesurrounding temperature and humidity levels and reacts in view of this.

� Amy Wilson, Architen Landrell Associates Ltd� [email protected]� www.architen.com

3 AWARDS FOR FABRITEC STRUCTURESFabriTec Structures garnered three awards in the 2008 International Achievement Award (IAA) competition presented by the Industrial Fabrics AssociationInter national (IFAI) for its exceptional specialty fabric projects. FabriTec won Outstanding Achievement awards for Grier Pavilion (Figure 1); a dazzlingoutdoor pavilion located on the top floor of the Riverside, California City Hall and for their Holiday Inn Palm Springs project (Figure 2); a high techentryway structure which has become a unique focal point for the local landscape. The company also earned an Award of Excellence for their Santa Fe OperaHouse project (Figure 3). The custom tensile structure covers an outdoor eating and lecture area and is a visually stunning addition to the beloved OperaHouse. For 61 years, the International Achievement Awards have recognized skilful design, technological innovation and excellence in the specialty fabricsindustry. FabriTec Structures has won several IAA awards in past years and is one of the five brands of USA SHADE & Fabric Structures, Inc.. The companyhas experienced professionals in specialty construction and handles every aspect of the job including 3D/CAD Design & Concept Development, Engineering,Steel and Fabric Fabrication, Manufacturing, Project Management and Construction.

EAT STREET WESTFIELD LONDON NORTH WEST BUS INTERCHANGE

GOOD DESIGN AWARD 2008The Nomad Concept together with Art Collective l’Anverre receivedthe “Good Design Award 2008” for the product ‘Umbellae’ (parasol).The strength of the product derives from the esthetic and the technicalpart of the design. Parasol ‘Umbellae’ is storm resistant and has aninnovating closing mechanism.

� Amandus VanQuaille, Architect The NOMAD CONCEPT� [email protected]� www.nomadconcept.com

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� Sarah van Wezel, USA SHADE & Fabric Structures, Inc

� [email protected]

� www.usa-shade.com

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