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TitleBending-active Structures A Case study for an Office Chaise Lounge

Permalinkhttps://escholarship.org/uc/item/41j5c79s

AuthorsPanagoulia, EleannaSchleicher, Simon

Publication Date2016

Copyright InformationThis work is made available under the terms of a Creative Commons Attribution-NonCommercial-ShareAlike License, availalbe at https://creativecommons.org/licenses/by-nc-sa/4.0/ Peer reviewed

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Bending - active Structures

A Case study for anOffice Chaise Lounge

Eleanna Panagoulia1, Simon Schleicher21Foster + Partners 2College of Environmental Design (CED), University of Cali-fornia, Berkeley1eleannapan@gmail.com 2simon_s@berkeley.edu

This paper seeks to explore the process of elastic bending in furniture design andpresents a case study that demonstrates the creative and structural potential ofbending-active structures as possible improvement to the current state of the art.This case study brings together design procedures, borrowed from declarativedesign in software engineering, architectural design, and material science inorder to envision new applications for bending-active structures. It investigateshow bending can be used strategically for the design of furniture scale objectsand, particularly, an office chaise lounge for one person. Active-bendingimplementation is the key for creating structures that achieve new milestonesbeyond the perceived limits of material and process. Moreover, the project standsas a great opportunity for the development of a pipeline for fabrication thatautomates the translation of a given high-level description of a design, to theproduction of the data required for fabrication via a particular material system.

Keywords: Bending-active structures, Matter compiler, Optimization

INTRODUCTIONArchitectural practice has been significantly influ-enced by the development of cutting-edge designtools that have set the scene for new ways of under-standing complex forms, analyzing their constraints,and optimizing their performance accordingly. Lat-est improvements in software and the increasing ac-cessibility of design tools have allowed designers toshift from a purely experimental state of extensivetrial and error, towards a more scientific integrationof design constraints to enrich the design process.Current design tools allow for additional parame-ter integration beyond formal description, such asphysics, material properties, or environmental con-

straints. Designers are able to integrate those factorsalready in the early stages of the design process bysimulating forces, structural performance, andmate-rial behavior accurately. This paper will focus on ac-tive, elastic bending in plate structures and will ex-plore the formal and structural possibilities that areavailable through bending, both as a form-findingmethod, as well as a strategy for achieving challeng-ing structural performance. Elastic bending in platestructures has already been implemented at variousscales. In this paper we will examine the principlesof elastic bending and its benefits at furniture scaledesign, by analyzing a case study for an office chaiselounge. In order to provide an informative frame-

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work for our research on elastic bending in furnituredesign, we will analyze the groundwork of bendingin furniture design through a series of examples thatoperate as precedent studies on the field.

BENDING IN FURNITURE DESIGN

Figure 1Left: MatthiasPliessnig, Amadabench [4], Right:CODA office, Grazchair [8]

Amajor innovation that designated substantially thedesign of mid 20th century and beyond, was the in-troduction of bending in furniture design. The firstmethod that was implemented in furniture and par-ticularly chair design, was bending bymeans of heat-forming. Heat-forming enabled the creation of nat-ural and organic shapes that were refreshingly dif-ferent in their aesthetic to the previously used mod-ernistic standardized forms. The strategic use ofbending made it possible to fabricate furniture withless pieces, which had great impact in preserving thecontinuity and fluidity of the overall form. However,bending was not only implemented to increase theaesthetic value of the design. Moreover, many de-signers recognized that bending as a novel fabrica-tion techniquewas a real paradigm shift that had thepower to revolutionize furniture industry by signifi-cantly reducing production costs.

Heat - Forming Bending PlywoodOne of the most suitable materials for heat bendingapplications was plywood. Plywood veneer offereddesigners the flexibility not only to explore morecomplex forms but also allowed for manual post-processing and premium quality finish. Another ad-vantage of using plywood bending was the possi-bility to accommodate the comfort factor, as theseshapes were friendlier to the human body geometry

and usually had nice tactile qualities. The most com-mon heat-forming process was steam bending of adried piece of lumber or a multilayer arrangement ofplywood veneers that are bound together with gluewith their grains perpendicular to each other. Theshape is givenwhen the structure is bent under pres-sure with heat. Here, hot steam was a particularlysuitable medium since it was able to penetrate deepinto the plywood tomomentarily soften its fibers andenabling it to be bent in multiple directions. Then,the plywood is let to cool down in order for the defor-mation to become permanent. Unlike natural wood,the resulting material does not have the same ma-terial properties at the final state, as it is less likelyto split when exposed to moisture. The shipbuild-ing industry was an early adopter of this techniquefor forming the curved members used to build ship'shulls. This paper will portray three examples of heat-formed furniture design, twoofwhich are consideredto be primary pioneers in themid 19th and 20th cen-tury and a third example that represents its contem-porary evolution nowadays.

Examples of heat-formed furnitureMichael Thonet, Chair No 14. The first example isMichael Thonet's Chair No 14. Thonet made signifi-cant advancements in steam bending techniques forchair design and he patented the process of multi-ple plywood veneer lamination. He also managed tostandardize and refine the existing techniques thatwere based in empirical know-how solely by spe-cialized craftsmen and incorporate it in the indus-trial process. Hence, Thonet engendered an assem-bly line of bent furniture that could be flat packedergonomically and easily assembled, an idea that isthe progenitor of the IKEA assembly line. Thonet'sChair No 14 expresses and elegant and ergonomicdesign that involved 6 pieces of steam-bent woodrods that were easily disassembled and flat packedfor transportation. Thonet minimized not only thenumber of pieces, but also the number of joints andconnections. Thonet was competing on the sector ofcafe chairs and he outperformed the cast-iron com-

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petitors with a much cheaper and lighter alternative(based on bent plywood). The Chair No 14 was veryeasy and cheap to produce by unskilled workers. Itbecame vastly popular across the U.S. and Europeand sold millions of units.

Charles and Ray Eames, Lounge Molded Chair(LCW).The secondexample is theChaise LoungeandtheMoldedPlywoodChair byCharles andRay Eames.The Eames have pioneered in inventing strategiesto craft complex forms. They experimented withwood molding techniques and developed strategiesto achieve curved complex forms out of planar, thinsheets of plywood. One of their main design driverswas to develop a compound-curved chair that ei-ther consisted out of very few or even a single shellsingle-shell. To accomplish this goal, the Eames in-vented their own machine to press large-scale ply-wood sheets, which enabled for example the mold-ing of unprecedented large aircraft parts (Eames2012). Prior to furniture, the Eames took advantageof bending characteristics (elasticity, resilience), tomanufacture stretchers and crutches for the WorldWar II. Later on, they implemented a similar strategyin furniture design and their pioneer methods hada profound effect in the way future designers per-ceived form and matter. However, due to the lim-its of the plywood itself, they were unable to makea single-piece shell out of molded plywood as origi-nally intended. Only years later they found a way toproduce the single-shell chair they were striving for,by using a new material that has never been used infurniture before: plastic.

Matthias Pliessnig, Amada Bench. The third exam-ple is the steam bent benches of Matthias Pliessnig(Figure 1). Pliessnig reframes heat bending throughthe lens of contemporary digital craft and he is inter-ested mainly in human proportion integration. Hisdesign is characterized by minimal shapes inspiredby wave flow and fluid dynamics in general. Pliess-nig's design combines craftsmanship and comfort,structural stability and strength with sculptural fi-nesse (Pliessnig 2010). As Pliessnig became familiarwith surface modeling tools, such as Rhinoceros, he

discovered similarities in theway the geometry is de-scribed within the digital environment and the waya boat scaffold is constructed. Same as is in boatshell constructions, there are leading ribs that des-ignate the shape as cross section elements and sec-ondary curves that bend along the ribs, forming acurved grid. Pliessnig implemented the exact samelogic in his bench design. The workflow that he de-veloped starts from a digital model and then contin-ues with constant refinement of the heat bent piecesuntil a perfectly smooth surface is achieved. He startsby drawing a free-form shape and then contouringit in temporary wooden ribs that are CNC cut andput along the target outline curve. Then he bendstemporary wooden slats, which he calls "SketchingStringers" (Pliessnig 2010), because they operate asguides to visualize the overall shape. After replace-ment of all temporary pieces, he steam bents finalslats until they form a continuous surface. Lastly,he strengthens the structure with epoxy and pins atthe intersections and sands the surface in order tobecome as smooth as possible. Pliessnig's benchesclearly address the notions of variability and fluiditycombined with ergonomics to suit the human body,as well as evident beauty and elegance.

ELASTIC BENDING AND BENDING-ACTIVESTRUCTURES

Figure 2Digital simulationof bending processin Kangaroo Physicsand SOFiSTiK(Schleicher et al.2015)

While the key concept behind the previous examplesis based on bending as means of plastically deform-ing a structure, the following case study will intro-duce and investigate the alternative of elastic bend-ing as active and holistic forming process for shapeexploration. Movingaway fromsteambendingappli-

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cations, we will now investigate elastic active bend-ing as a holistic process that addresses form explo-ration, as well as structural performance integration.The term "bending-active" is introduced by Knipperset al. to describe curved beam and surface struc-tures that base their geometry on elastic deforma-tion of initially straight or planar elements (Knipperset al. 2011). Active bending can be defined as aform-finding process that derives from the elastic de-formation of a rod or plate structure. It is a processthat creates curved geometry out of planar, straightmembers or surfaces (Figure 2). One of the key as-pects of bending-active structures is that they devi-ate from the existing structural typologies, such asspace frame structures, planar or curved trusses etc.As Lienhard et al. explains, bending-active struc-tures are distinguished as an approach rather thana distinct structural typology (Lienhard et al. 2014).This is because they allow for heterogeneous config-urations and nonlinearities in their load bearing be-havior. The latest advancements in Finite ElementAnalysis software (FEA) (Piker 2013, Lienhard et al.2011) allow engineers to analyze and simulate struc-tures beyond the existing typologies with a highlevel of accuracy in the load calculation. Bending-active structures offer a wide field of experimenta-tion onnon-standard load configurations, as they de-rive their complex geometry from elastic deforma-tion processes. Finally, in comparison to the pre-vious existing structural typologies, in the resultinglightweight structures, bending is not avoided butinstrumentalized to create complex curved geome-tries on the basis of standard, semi-finished buildingproducts. A particular advantage of this approachto construction (design approach to bending-activestructures basedonelastically deformedmembers) isthe opportunity to continue using conventional flat-basedmanufacturing processes but in an unconven-tional way. As usual, parts can be produced on CNCrouters, laser cutters, and waterjets in a cheap, quick,and reliant manner. As is newly introduced with myresearch, the materials then get bent and coupledtogether to form highly complex origami-like struc-

tures. This fabrication method provides a very timeand material efficient alternative to traditional con-struction processes since it is neither depended onthe fabrication of expensive molds nor on the auxil-iary support of complicated formwork. Before mov-ing on to the case study that this paper mainly fo-cuseson,wewill examineanexampleof elastic bend-ing plywood in chair design.

Elastic bending of plywwod, CODA GrazChairThe Graz chair by CODA office (Figure 1) is an out-standing example of elastic bending plywood andhas operated as a precedent for our case study. Theoriginal design is a revision of theMedea chair by Vit-torio Nobili that suggests improvements in the fabri-cation methodology and the quality of the plywoodlayers. The design suggests a flat, rectangular pieceof plywood that carries some CNC smart slits. Whenthe naked edges of the slits are overlapped and con-nected, the shape of the chair is formed. The ground-breaking idea of this design is that it achieves dou-ble curvature without requiring expensive, special-ized equipment or craftmanship as the previous ex-amples. It also allows for customization and adapt-ability in a wide range of target shapes. These princi-pals influenced our design andmotivated us to pushthe boundaries further, explore more complicatedshapes and achieve stability by a single operationmethod (in our case, elastic bending of flat surfaces).

Bending-active as a form finding processForm-finding is generally understood as the pro-cess of developing the geometric form of a struc-ture based on mechanical behavior (Lienhard et al.2014). This means that the resulting form is desig-nated by a particular set of loads that operate onit within a constrained set of parameters (material,scale). In bending-active structures, since the formderives fromanelastic deformationof a planar shape,the resulting geometry is hard to predict with highaccuracy without a real time bending simulation.Computational tools such Kangaroo Physics, or FEAsoftware allow the user to apply loads on a struc-

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ture and simulate the deformation in real time andtherefore; observe the result as well as the interme-diate steps of the simulation. Having real time feed-back from the process, the user is able to better un-derstand the relationships between the variables ofthe system and adjust them until the desired resultis achieved. Although this process offers the userfreedom to explore new forms, it is worth mention-ing that form-finding result does not necessarily cor-respond with the most efficient load-bearing solu-tion. Hence, themain challenge is to optimize the setof variables to a functioning relation that addressesboth aesthetic qualities, as well as sufficient load-bearing capacity and stability. Furthermore, to suc-cessfully create a bending-active system it is impor-tant to incorporate material properties, as well as toexperiment with physical modeling. Wewill examinethe contribution of physical scaled models in the fol-lowing sections of the paper.

HOLISTIC DESIGN PROCESSBased on what was mentioned above, this sectionwill describe the design process that was imple-mented in the chaise lounge case study. The goalof this case study is to achieve an optimum balancebetween comfort, stability, easier material handling,weight and cost. To achieve that we will start fromidentifying two strategies, in which the design pro-cess was based on.

Matter CompilerThe first strategy of the design process suggests theconstruction of a continuous workflow that is called"Matter Compiler". This approach borrows some ofthe principals of declarative design (Bachrach 2012)in software engineering. It promotes a pipeline oflinked processes that are automated in order to re-duce large manual effort and enhance the search forbetter and more efficient designs. The matter com-piler suggests the building of a system with con-tributing variables, such as forces, material proper-ties, human proportions etc. where all the processesare part of a single workflow that transfers data from

one phase to the subsequent. The benefits of a con-tinuousworkflow lie on the fact that the designer op-erates at a high level set of intentions for the design,such as overall size, number of users, seating postureetc. and the system translates them in a set of instruc-tions for fabrication.

Accommodating comfortThe second strategy that defined the design processwas that of body conscious design (Cranz 2000). Oneof the objectives of this case study was to improvethe basic configuration of the conventional seatingposture. To achieve that, we analyzed seating pos-tures of existing furniture and ended up in choosingthe chaise lounge posture as one of the most com-fortable and with the best stress and load distribu-tion for the body (Figure 3). Lounging, which can bedefined as halfway sitting and lying down, takes loadoff the spine neck and head. After analyzing in detaildesigners' chaise lounges as precedent models andas role models for the correct angles that fit the hu-man body, we ended up isolating the main variablesthat are associated with the comfort factor. Thesevariables are, the points of contact with the humanbody (arms, hands and legs), the alignment and sup-port requirementsof thosepoints and theangles thatare formed between the points of contact.

CASE STUDY: BENDING CHAISE LOUNGEThis section will delve into a more detailed analysisof the processes that are engaged in the case study,from form-finding methodologies to fabrication andassembly.

Form-Findingmethod: PinchingThis case study approaches bending-active struc-tures topic under the lens of minimal material em-ployment, in order to prototype a chaise lounge outof theminimumamount of bended surfaceswith thehighest structural performance. A geometrical inspi-ration that gave direction to the form-finding pro-cess was the exploration of conical bending. Inspiredby Plücker's conoid as reference geometry enabled

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Figure 3Angle study ofprecedent designs,Final pieces of theprototype

Figure 4Prototype chaiselounge built out of1:16" thicknessHDPE sheets

us to formulate a methodology for achieving simi-lar shapes out of planar surfaces and examine theirstructural performance. The method we resulted inis called pinching and it is described as the processof strategically removing an internal part of a planarsurface and connecting the naked edges of the cutout shape, allowing the surface to bend accordinglyin three dimensions (Figure 5). The main motivationfor the pinching method lies in the simplicity of pro-ducing complexly curved elements. This process ap-pears to have two benefits: first, it produces intri-cate shapes out of a single planar surface; second, itcreates three-dimensional shapes thatperformstruc-

turally in the bended state.

Figure 5Pinching as aform-findingtechnique

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Matter Compiler: Steps and Processes

Figure 6Digital simulation inFEA softwareSOFiSTiK

As stated above, the pipeline used for this projectsuggests the use of a "Matter Compiler" that trans-lates high-level descriptions of a set of intentions orthedesign to low-level instructions for digital fabrica-tion and construction documentation. This methodis constrained by a particular material system, a spe-cific method of joining/assembly and a specific pro-cess of fabrication. Our compiler suggests the follow-ing main steps:

• Form-finding• Geometric rationalization• Joints and seams handing• Layout automation - Fabrication

The following paragraph describes the workflow interms of types of processes, relationships and in-cluded variables. The first step involves the FormFinding process that was rendered through thepinching methodology that was described above.This involves a parametric model of the planar sur-face with the cut out shapes. The first simulationswere done in the Grasshopper plug-in KangarooPhysics and later in the Finite Element Analysis soft-ware SOFiSTiK (Figure 6). The Finite Element Analysisproduced more accurate results, as we were able tocalculate the stress and loads along the surface andobserve the stress distribution. Alongwith the digitalsimulations, a large part of the form exploration wascarried out with physical models. The physical exper-iments were scaled models of either paper or the ac-

tual material in smaller thicknesses that were createdfor actual material testing and for cross-referencingthe results of the digital simulation. The second stepinvolves geometric rationalization of the outcomeshape, in order for it to adapt to the human bodyproportions and ergonomics. We created differentfamilies of cut out shapes along the planar surfacethat correspond to different angles when the surfacebents in three dimensions, hence this leads in achiev-ing postural variation. Based on the analysis that wascarried through in precedent chaise lounges, we de-pict target angles andproportions that lead to a com-fortable seating posture. The third step consists ofthe handling of joints and seams. In our case, thejoining of the naked edges is by the technique ofriveting and particularly, blind riveting. The samemethod is used to join multiple surfaces together.Rivets were preferred because they can support ten-sion loads, as well as shear loads. Riveting is achievedby the creation of parametric tabs along the givenedge with a number of holes at a certain distancefromeachother that overlap completely and are con-nected with blind rivets. Having said that, it is ap-parent that given a modification in the length of theedge, due to form adjustment, the tabs and the holepattern adjust accordingly. For the riveting processwe used steel rivets and washers, as well as a rivetgun. The fourth and final step of our compiler is thelayout automation that provides the data for fabri-cation. Since the main goal of this project was toachieve best structural performance, while using theminimum amount of joints and pieces, the layout au-tomationprocess is a straightforward 2Dnestingpro-cess of few planar outlined shapes in 4ft. by 8ft. pla-nar sheets.

MaterializationIn this section we will analyze all the contributingprocesses from design to construction of the chaiselounge. We will divide the processes in two cat-egories, high-level and low-level intentions. High-level intention processes are those, which affect pri-mary properties of the design, such as comfort, aes-

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thetic, size, proportions, stiffness, stability etc. Low-level intentionprocesses are those,which are respon-sible for the production of the prototype, such as, de-tailed shape refinement, tab creation for assembly,hole pattern for the rivet joints and data for fabrica-tion. Low-level intention processes translate the dig-ital, optimized model into a set of components thatare constructible by the chosen fabrication equip-ment within a set of feasibility constraints.

Form development and Optimization. Investigat-ing further the technique of pinching, which was de-scribed above as a form-finding strategy, the furtherdevelopment of the design was to define the cor-relation between angle of cut out shape and angleof bended shape. In that way we would be ableto test the ergonomics, angles, lengths and propor-tions and make the necessary adjustments. The ini-tial test models included symmetrical shapes (circle,ellipsoids), in order to assess the relationship of the2D shapes with the 3 dimensional bent forms (Fig-ure 5). The relationship between the elements waslinear for most cases, meaning the wider the angleof the cutout, the smaller the bending radius was,causing higher deformation to the surface. Once aprincipal model was developed, the variation of an-gles and proportions allowed for fine calibration ofthe geometry. The modifications concentrated onadjusting the angles of the cut out shapes, so that thebended outcome shape is comfortable and adaptedto the human body. Hence, the outlines (exterior, in-terior) of the planar surfaces were optimized to re-spond both in terms of functionality; the object hasto perform as a chaise lounge, as well as in termsof structural stability; the object has to support theweight of a personwithoutmaterial breach. The finalshape of the chaise lounge was determined by sim-ulating the planar surface with cutout shapes in theright locations and sizes, with a given load set. Thebending simulation was processed in the Finite Ele-ment Analysis software, SOFiSTiK, following the elas-tic cable approach. This approach involves definingthe fixed and sliding points of the geometry, as wellas contraction cables that join the naked edges of the

planar surface causing elastic deformation. The sim-ulation terminates, when the cables' length reachesthe value of zero.

Material depended geometry. Along with the formdevelopment strategy to address comfort, the pro-cess of high-level description of the design involvesmaterial property integration, such as the minimumbending radii and the Young's Modulus of the mate-rial, in order to predict and exclude in advance cer-tain dimension ranges that would causematerial fail-ure. The material system chosen in this project is 4ft.by 8ft. high-density polyethylene (HDPE) sheets of1/16" thickness with a Young's Modulus of 1200N /mm2 . The material itself, when in the flat state, didnot demonstrate characteristics of stiffness, howeverwhen bent, it provided enough stability to hold theweightof oneperson. The simulationaidedus tobestutilize material resilience and strength when bent,by providing numerical feedback regarding the loadsand stresses along the bent shape. As mentionedbefore, along with the digital simulation, we carriedout multiple physical experiments. Experimentingwith physical models speeded up the optimizationprocess, because it allowed an instant understand-ing of the load and stress distribution, as well as theassociation of the variables with resulting geometry.However, scaledmodels tended to appear stiffer thanthey actually operated in 1:1 scale and the same typeof material demonstrated different properties in dif-ferent scales. This condition had to be studied care-fully in the digital simulation in order to make surethat thematerial used in the prototype demonstratesthe desired properties.

Low-Level processes. The Low-level process in-cludes four processes. The first process includes therefinement of the bended shapeby trimming and ad-justing the outline of the bended shape in order for ittomeet thedesired shapeexpectations, such as fillet-ing sharp corners and removing unwanted materialfromareas that do not affect the structural stability ofthe chaise. Since shape refinement can only happenwhen the surface is bent and the chosen method offabricationoperates in 2-dimensional shapes only, an

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additional process is required. This process involvesthe re-flattening of the bended surface, in order toget the exact outline of a planar surface for fabrica-tion. This process is necessary because the bendedshape cannot be predicted before simulation; there-fore the refinement takes place after the bendingprocess. However, since our fabrication method ap-plies only to flat surfaces, re-flattening the bendedsurface after bending is required. The secondprocesssuggests the creation of tabs along the edges of theinterior cutout shape that are important for connect-ing the edges together. In this project we explore thelimitations of this technique in terms of dimensionconstraints, as well as the maximum material thick-ness where rivet joining is still effective. The tabs hadto provide sufficient surface area for the rivets to beplaced in a way allows equal stress distribution alongthe tab surface to avoid tearing. Also, i is importantto mention that the calculation has to be as exact aspossible so that when all the tabs of the structure,the hole pattern will much so that the rivets can passthrough the holes. Any discrepancy in the simulationor the generation of the tabs would cause difficultiesin the assembly process. The third process involvesremoval of material in areas of high stress concentra-tion. Based on the minimum-bending radius of thematerial and the stress information from the simula-tion we were able to allocate areas of high stress dis-tribution that would cause the material to tear. Toavoid that, we strategically removed those areas be-fore the bending so that they are within the range ofthe bending radius of the HDPE polymer sheet. Thefourth and last process is nesting the pieces in 4ft. by8ft. HDPE sheets for fabrication. The overall shapeof the chaise lounge is composed by 2 bended sur-faces connected in 3 critical areas, in order to providestrength to the structure, as well as a third smallersurface that creates tension in the whole structure,preventing it from self-load deformation. The fab-rication method that is most suitable for this mate-rial, in terms of cost, speed (1 hour setting up andcut time) and accuracy is cutting in the "Zund" bladecutter (tool: blade Z10, setting: multi-pass, 3 passes).

(Figure 4, Figure 7)

CONCLUSIONThe objective of this paper was to provide generalinsight into form-finding and structural analysis ofbending-active structures. The work aimed to ex-plore the potentials of bending-active structures infurniture design as an approach in generating newforms and structural strategies. Briefly, the parts ofthe case study that were considered successful werethe accurate translation of software results into fab-rication, as well as the accurate simulation of angles,forces andmaterial property integration that resultedin a comfortable chaise lounge that can bear the loadof one person. It is worth mentioning that the over-all cost of the chaise was low (around 100 USD) and itwas ightweight in relation to its size and loadbearingcapacity (around 20 kg). A future development of theproject would be a larger design space explorationthat would respond to a wider range of demands,in terms of functionality and use, such as fit multi-ple people, accommodate extreme load cases withlocal material reinforcement. Also, in terms of join-ery and assembly, the possibility of disassemblingand re-assembling the chaise lounge, by introducingtemporary, yet strong connections would be desir-able. Another aspect that is definitely worth lookinginto would be the use of amore sustainablematerial.However the challenge would be to allocate a ma-terial with similar structural properties. The poten-tial of plywood as we saw in the Graz chair examplewas considered, but was excluded eventually due tothe large bending radii that it requires. Moreover, wewere aiming for an easier handling in terms ofweightand fabrication speed. Before ending up choosinghigh-density polyethylene (HDPE), we ran some testswithpolystyreneaswell aswith lowdensitypolyethy-lene. The results were disappointing in terms ofstructural stability and stiffness, as Polystyrene wastoo brittle and low density polyethylene (LDPE) wasnot stiff enough. Apotential answermight be lying inrecycled High-density polyethylene, in case it main-tains its original properties after the recycling pro-

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Figure 7Prototype chaiselounge built to of1:16" thicknessHDPE sheets, proofof concept

cess, however this is a topic that needs to be lookedinto and experimented upon.

ACKNOWLEDGMENTSThis work was conducted as part of Studio One2014/2015 and the Bending and Folding Seminar atUC Berkeley's College of Environmental Design at theDepartment of Architecture. The case study was ateam work of Cindy Hartono, Fei Du, Shima Saheb-nassagh, Eleanna Panagoulia under the supervisionof Prof. Kyle Steinfeld Prof. Simon Schleicher, Prof.Jonathan Bachrach and Luis Jaggy and generouslysupported by Autodesk. The authors want to partic-ularly thank all member of the team: Cindy Hartono,Fei Du, Shima Sahebnassagh, Eleanna Panagoulia.

REFERENCESCranz, G 2000, The Chair, Rethinking culture, body , and

design, w. w. Norton & Company, New York, LondonEames, D 2012, Eames: Beautiful Details, AMMO Books,

Los Angeles, CA

Knippers, J, Cremers, J, Gabler, M and Lienhard, J 2011,Construction Manual for Polymer Membranes: Ma-terial, Semi-Finished products, Form-finding Design,Birkhauser Achitecture, Basel

Lienhard, J 2014, Bending-active Structure, Form findingstrategies for elastic deformation in static and kineticsystems and the structural potentials therein, Ph.D.Thesis, Institute of Building Structures and Struc-tural Design University of Stuttgart

Schleicher, S, Rastetter, A, Schönbrunner, A, Haber-bosch, N and Knippers, J 2015 'Form-Finding andDesignPotentials of Bending-ActivePlate Structuresin Modelling Behaviour', Proceedings of Design Mod-elling Symposium 2015

[1] http://www.eecs.berkeley.edu/˜jrb/Projects/declarative-design/declarative-design.htm

[2] http://en.thonet.de/service/press/history-214.html

[3] http://global.rakuten.com/en/store/chaoscollection/item/eames_lcw_walnut_p/

[4] http://www.designboom.com/design/matthias-plies

snig-amada-bench/[5] http://www.eamesoffice.com/the-work/airplane-fu

selage/

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[6] http://www.sofistik.com/en/[7] http://en.thonet.de/[8] http://coda-office.com/work/Graz

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