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integration through computationacadia 2011 _proceedings
In contrast to most other building materials, wood is a naturally grown biological tissue. Today,
the organic nature of wood is recognized as a major advantage. Wood is one of the very few
naturally renewable, fully recyclable, extremely energy efficient and CO2-positive construction
materials. On the other hand, compared to industrially produced, isotropic materials, the
inherent heterogeneity and differentiated material makeup of wood’s anatomic structure is still
considered problematic by architects and engineers alike. This is due to the fact that, even
today, most design tools employed in architecture are still incapable of integrating and thus
instrumentalizing the material properties and related complex behavior of wood.
The research presented in this paper focuses on the development of a computational
design approach that is based on the integration of material properties and characteristics.
Understanding wood as a natural composite system of cellulose fibers embedded in a lignin and
hemicelluloses matrix characterized by relatively high strain at failure, that is high load-bearing
capacity with relatively low stiffness, the particular focus of this paper is the investigation of how
the bending behavior of wood can become a generative design driver in such computational
processes. In combination with the additional integration of the possibilities and constraints
of robotic manufacturing processes, this enables the design and production of truly material-
specific and highly performative wood architecture. The paper will provide a detailed explanation
of such an integrative approach to design computation and the related methods and techniques.
This is complemented by the description of three specific research projects, which were
conducted as part of the overall research and all resulted in full scale prototype structures. The
research projects demonstrate different approaches to the computational design integration of
material behavior and robotic manufacturing constraints. Based on a solution space defined by
the material itself, this enables novel ways of computationally deriving both material-specific
gestalt and performative capacity of one of the oldest construction materials we have.
Integrative Design Computationintegrating material behaviour and robotic manufacturing processes in computational design for performative wood constructions
Ach im Menges
Stu t t ga r t Un i ve r s i t y
Ha r va rd Un i ve r s i t y
ABSTRACT
73
Figure 1a. Madan Houses (Oliver 2007)
Figure 1b. Hooke Park (Nerdinger 2005)
Figure 1c. Hooke Park
computation, formation and materiality
Fig. 1a
Fig. 1b
Fig. 1c
1 Introduct ion: Integrat ive Design Computat ion
In arch i tecture, computat iona l des ign processes have been invest igated in numerous
ways over the last 50 years. In para l le l to the deve lopment of Computer A ided Design,
which is character ized by the t ransfer of long-estab l ished, representat iona l des ign
techniques in to the d ig i ta l rea lm, research in to generat ive Computat iona l Des ign has
been conducted for many decades. In the 1960s des ign programs such as GRASP
(generat ion of random access s i te p lans) deve loped by Er ic Te icholz at the Harvard
Laboratory for Computer Graphics, exp lored ways of generat ing rather than drawing
des ign so lut ions and eva luat ing the i r per formance (Howard 1998). Unt i l recent ly,
par t icu lar ly dur ing the last two decades, a wide range of generat ive computat iona l
des ign techniques have been both researched in academia and tested in pract ice
(Mark, Gross and Goldschmidt 2008). Rather than determin ing form, as is emblemat ic
for CAD, most of them share a conceptua l izat ion of des ign as a process of der iv ing
arch i tectura l form through the generat ion and a lgor i thmic process ing of in format ion
(Terz id is 2006). Thus form is understood as resu l t ing f rom the in teract ion of a
def ined system and externa l data, and d isp lay ing a par t icu lar per format ive capaci ty
when eva luated aga inst def ined des ign cr i ter ia . In th is way, form, in format ion, form
generat ion and per formance are inherent ly re la ted, and the degree of in tegrat ion
main ly depends on the number of system parameters and des ign cr i ter ia embedded
and eva luated in the computat iona l process. However, i t is in terest ing and important to
note that th is in tegrat ion, and re la ted in format ion feedback respect ive ly, is s t i l l most ly
l imi ted to “system-externa l ” aspects such as, for example, env i ronmenta l or economic
cr i ter ia , whereas the “system- int r ins ic” mater ia l character is t ics and phys ica l behav ior
are hard ly ever cons idered or ut i l i zed (Menges 2008).
The la rger research pro jec t th is paper is based on a ims fo r deve lop ing a computa t iona l
des ign approach tha t syn thes izes per fo rmance-or ien ted fo rm genera t ion and
phys ica l p rocesses o f mater ia l i za t ion. Here, the des ign space is de f ined and
const ra ined by mater ia l behav io r, fabr ica t ion and product ion. Th is unders tand ing o f
des ign computa t ion as a ca l ib ra t ion between the v i r tua l p rocesses o f genera t ing
fo rm and the phys ica l becoming o f mater ia l sys tems, shou ld not be conce ived as
l im i t ing the des igner, but ra ther as enab l ing the exp lo ra t ion o f unknown po in ts in
the search space def ined by the mater ia l i t se l f (Menges 2010) . In o ther words, th is
research s t r i ves fo r cont r ibu t ing to the fu r ther deve lopment o f computa t iona l des ign
by invest iga t ing [ i ] how mater ia l behav io r can be in tegra ted in genera t i ve des ign
computa t ion, [ i i ] how th is in tegra t ion requ i res not mere ly a CAD-CAM cha in but ra ther
an in fo rmat ion feedback between the degrees o f f reedom and const ra in ts o f robot ic
manufactu r ing and mater ia l a f fo rdances, and [ i i i ] how such processes can prov ide fo r
the deve lopment o f nove l , per fo rmat i ve a rch i tec tu ra l mate r ia l sys tems.
2 Integrat ing Computat ional Form Generat ion and Physical Behaviour
Based on the a fo rement ioned la rger research agenda, th is paper w i l l concent ra te
on par t icu la r aspects o f mater ia l behav io r, the actua l mate r ia l make-up dete rmin ing
th is behav io r, and the fabr ica t ion processes tha t a l low fo r exp lo i t ing th is mater ia l
behav io r. The focus w i l l be on the e las t ic bend ing behav io r o f robot ica l l y fabr ica ted
wood e lements . The reasons fo r th is a re th ree fo ld and exp la ined in the fo l low ing
paragraphs:
1. E las t ic bend ing as both a fo rm- f ind ing and const ruc t ion techn ique is s t i l l
re la t i ve ly uncommon. Desp i te the cons iderab le per fo rmat i ve capac i ty o f e las t ica l l y
bent s t ruc tu res, th is may be due to the fac t tha t a rch i tec ts and eng ineers a l i ke
s t i l l l ack too ls fo r des ign ing w i th geomet r ica l l y ins tab le e lements . A lso, s t ruc tu ra l
eng ineers a re genera l l y t ra ined to unders tand la rger de fo rmat ions as prob lemat ic
and potent ia l l y damag ing. Because o f the cons iderab le techn ica l and in te l lec tua l
d i f f i cu l t ies posed by a synchronous cons idera t ion o f fo rce, fo rm and per fo rmance,
there a re on ly ve r y few cases o f e las t ica l l y -bent a rch i tec tu res, as fo r example the
Madan peop le ’s ve rnacu la r s t ruc tu res o f bent reed bund les in I raq (F igure 1a) , o r
the wooden she l l s t ruc tu res a t Hooke Park in Eng land (F igures 1b/c) , wh ich were
co l labora t i ve ly des igned by F re i Ot to , ABK and Buro Happo ld , and const ruc ted f rom
e las t ica l l y bent g reen round-wood po les prov ided by loca l fo res t th inn ing.
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integration through computationacadia 2011 _proceedings
Figure 2a. White Oak (Copley 2011)
Figure 2b. Wood Cell (Dinwoodie 2000)
Figure 2c. Anisotropic E-Modulus (Dinwoodie 2000)
Fig. 2a
Fig. 2b
Fig. 2c
2. Wood is a complex mater ia l . In contrast to other more homogenous and isotropic
bui ld ing mater ia ls speci f ical ly produced for the demands of the bui ld ing sector, wood is a
natura l ly grown bio logical t issue character ized by a di f ferent iated f ibrous structure. Whi le
i t is commonly accepted by archi tects, engineers and craf tsmen al ike that the speci f ic
mater ia l make-up of wood needs to be considered in the design process, archi tectura l
design tools are not capable of integrat ing anisotropic mater ia l character ist ics and
behavior. Thus the complex anatomy of wood and i ts re lated behavior is of part icular
interest for an informat ion-based, computat ional design process.
3. Robot ic manufactur ing opens up the possibi l i ty of combining computer control led
6-axis k inemat ics with re lat ively common tools for wood working as, for example, rotary
saw blades and mi l l ing cutters. In the aforement ioned integrat ive computat ional design
process the large design space af forded by the var ious degrees of f reedom of the
industr ia l robot and i ts ef fector a l lows for speci f ical ly di f ferent iat ing bui ld ing elements in
the prefabr icat ion process, and thus extending the complex micro scale structure of the
mater ia l to the macro scale of the mater ia l construct ion. In th is way, the possible macro-
scalar di f ferent iat ion dur ing the manufactur ing process and consequent ia l manipulat ion
of the mater ia l e lement’s behavior needs to be integrated in the computat ional design
process. In addit ion, as the programming of a 6-axis robot is re lat ively complex and
t ime-consuming, the data output in robot control language needs to be an integral part
of the informat ion model for the fabr icat ion of large numbers of di f ferent iated elements.
Consider ing these three points the paper wi l l f i rst expla in the part icular anatomy of
wood, and how the microscopic f ibrous structure of wood governs the macroscopic
bending behavior of wood pieces. Thereafter, the presentat ion of three research projects
demonstrates di f ferent approaches to the computat ional design integrat ion: The f i rst
project explores the computat ional integrat ion of mater ia l and fabr icat ion parameters for
plast ical ly formed hardwood slats. For the construct ion of an intr icate, l ightweight lat t ice
structure the process var iables of steaming, bending and twist ing s lender white oak
members were embedded in a computat ional design tool. The second project invest igates
the possibi l i ty of programming the elast ic bending behavior of pre-steamed hardwood
slats by local ly di f ferent iated kerfs. In order to construct a fu l l scale, hyperboloid
prototype structure the mater ia l propert ies of whi te oak, the process var iables of wood
steaming and the fabr icat ion parameters of a 6-axis industr ia l robot equipped with a
ci rcular saw blade were integrated in a custom programmed design tool. This enabled
both the computat ional form-f inding of the system and the automat ic generat ion of the
re lated machine, which was di rect ly der ived as the required robot control language. The
th i rd project researches a computat ional design process based on the elast ic bending
behavior of b i rch plywood lamel las. These lamel las are robot ical ly manufactured as
in i t ia l ly p lanar e lements, and subsequent ly connected so that the force that is local ly
stored in each bent region of the str ip, and mainta ined by the corresponding tensioned
region of the neighbor ing str ip. The resul tant novel bending-act ive structure uses only
extremely th in plywood lamel las, which sett le into an equi l ibr ium state that unfolds a
unique archi tectura l space whi le at the same t ime being very ef f ic ient wi th the employed
mater ia l resources.
3 Integrat ing the Fibrous Structure, Di fferent iated Anatomy and
Anisotropic Behavior of Wood
As a natura l ly grown t issue, wood is s ign i f icant ly d i f fe rent to most other mater ia ls used
in the bu i ld ing indust r y. Whi le wood is one of the o ldest const ruct ion mater ia ls , i ts
organ ic nature is aga in understood as a s ign i f icant advantage, par t icu lar ly in the l ight
of the future env i ronmenta l cha l lenges of the bu i ld ing sector. As t rees main ly ut i l i ze
photosynthes is, that is so lar energy, for growth, and as they t ransform carbon d iox ide
in to oxygen dur ing th is processes, wood has an ext remely low leve l o f embodied
energy and a pos i t ive CO2 ba lance, even af ter undergoing today’s h igh ly indust r ia l
wood process ing. Thus, i f grown in susta inable s i lv icu l ture, wood is one of the very few
h igh ly energy ef f ic ient , natura l ly renewable, fu l ly recyc lab le bu i ld ing mater ia ls (Herzog
2003). As a consequence, a computat iona l approach to des ign ing wood const ruct ions
is of par t icu lar re levance. Even more so as the complex st ructure and re la ted mater ia l
behav ior of wood, which a lso or ig inates f rom i ts organ ic nature, lends i tse l f to an
75
Figure 3a. Steaming white oak slats
Figure 3b. Steamed slat forming figure
Fig. 3a
Fig. 3b
in format ion-based des ign process. Hence, any genuine wood-speci f ic computat iona l
des ign process needs to begin wi th an understanding of wood’s anatomy, as i t
accounts for most of i ts proper t ies and character is t ics (Hensel and Menges 2009).
Wood grows as the f ibrous, vascular t issue of t rees funct ion ing as both the load-
bear ing st ructure and metabol ic in f rast ructure for the l i v ing p lant organ isms. The
anatomy of wood has evo lved in response to these b io log ica l requi rements and thus
d i f fers cons iderab ly f rom other const ruct ion mater ia ls that are indust r ia l l y produced
and des igned to sat is fy the speci f ic demands of the bu i ld ing indust r y. These mater ia ls ,
for example stee l and g lass, are typ ica l ly homogenous, i .e. un i form in composi t ion,
and isot rop ic, hav ing equal or very s imi la r proper t ies in a l l d i rect ions. In cont rast ,
wood is not on ly subject to b io log ica l var iab i l i ty and natura l i r regu lar i t ies, wood’s
mater ia l make-up i tse l f is grown as a heterogeneous, an isot rop ic and h ierarch ica l
s t ructure. The reproduct ive t issues of t rees grow both on the t ips of tw igs (ap ica l
mer is tems) and as th ickness growth of the stem ( la tera l mer is tems) adding year ly
wood to the prev ious ly grown. The th ickness growth pr imar i ly takes p lace in a very th in
layer of ce l ls , the cambium between the inner s tem and the bark. Cambia l ce l ls d iv ide
to form another cambia l ce l l and a new ce l l that , depending on i ts pos i t ion, e i ther
matures as a bark or wood ce l l (Hoadley 2000). The ce l lu la r s t ructure of sof twood and
hardwood is re la t ive ly d i f fe rent . Whereas more than 90 percent of sof twood’s t issue
is composed of t racheids, which are long f iber- l ike ce l ls ar ranged para l le l to the stem
ax is, hardwood cons is ts of numerous ce l l types inc lud ing t racheids, vesse ls, rays and
f ibre ce l ls (Wagenführ 1999). The b i rch and whi te oak wood (F igure 2a) used in the
three research pro jects d iscussed in th is paper be long to the c lose ly re la ted hardwood
fami l ies of Betu laceae and Fagaceae.
Af ter the wood ce l ls are fu l ly grown to the i r f ina l s ize and shape, the inner sur face of
the f rag i le pr imary ce l l wa l l is re in forced by a s ign i f icant ly th icker secondary ce l l wa l l
cons is t ing of three layers (F igure 2b) . The ce l l wa l ls are const ructed f rom long cha in
ce l lu lose molecules main ly or iented para l le l to the ce l l ’s long ax is. The l inear po lymer
cha in of ce l lu lose is h igh ly ordered wi th densely packed molecules, resu l t ing in f ibrous-
l ike st rands ca l led microf ibr i ls . Th is ce l lu los ic st ructure is then re in forced by a matr ix o f
l ign in. The resu l t ing d i rect iona l composi te system accounts for many character is t ics of
wood (Barnet t and Jeron imid is 2003). The h igh ly d i rect iona l , para l le l a l ignment of the
ce l lu lose cha ins in the microf ibr i ls resu l ts in s t rongly an isot rop ic mechanica l proper t ies
(F igure 2c) . For example, wood has h igh tens i le and compress ive st rength para l le l
to the gra in d i rect ion, whereas i t is very low in compress ion or tens ion perpendicu lar
to the f ibre. S imi la r ly, wood’s modulus of e last ic i ty d i f fe rs s ign i f icant ly depending on
gra in or ientat ion: the modulus of e last ic i ty para l le l to the main f ibre d i rect ion, between
9000 to 16000 N/mm² depending on wood species, is genera l ly approx imate ly f i f teen
t imes h igher than perpendicu lar to the f ibres, which is between 600 to 1000 N/mm²
(D inwoodie 2000). Th is can be understood and inst rumenta l i zed as an in terest ing
proper ty of var iab le st rength and st i f fness in re la t ion to gra in or ientat ion (Wagenführ
2008).
S imi la r to synthet ic composi tes, e.g. , g lass f ibre re in forced p last ic, wood is
character ized by re la t ive ly h igh st ra in at fa i lu re, which means h igh load-bear ing
capaci ty wi th re la t ive ly low st i f fness. These mater ia l proper t ies and re la ted behav ior
are especia l ly wel l su i ted for const ruct ion techniques that employ the e last ic bending
of wood in order to form complex, l ightweight s t ructures f rom in i t ia l l y s imple, p lanar
bu i ld ing e lements, as the fo l lowing three pro jects wi l l demonst rate.
4 Performative Wood Construct ion
4.1 RESEARCH PROJECT 01: LATTICE SYSTEM CONSTRUCTED FROM STEAMED WHITE OAK
Bend ing so l i d wood i s a t r ad i t i ona l woodwo rk i ng t echn ique . As compa red
t o add i t i v e o r sub t r ac t i ve f ab r i ca t i on t echn iques , t h i s f o rm ing p rocess has
cons ide rab l e advan tages f o r p roduc i ng cu r ved wooden pa r t s : bend i ng wood i s
ma te r i a l l y ve r y e f f i c i en t and s t r uc tu r a l l y advan tageous , as i t r eo r i en t s t he g r a i n
d i r ec t i on t o f o l l ow t he pa r t ’s cu r va tu re , a vo id i ng excess i ve f i be r r un -ou t on t he
edges and c ross -g ra i n weaknesses .
computation, formation and materiality
76
integration through computationacadia 2011 _proceedings
Figure 4a. Computationally derived prototype
set-up
Figure 4b/c. Physical prototype structure based on
the bending behavior of steamed white oak slats
Fig. 4a
Fig. 4b Fig. 4c
The l imits of bending solid wood are defined by beam mechanics. In a bent beam, the
outer f ibers on the concave side are in compression and on the convex side in tension,
usually fai l ing at approximately one percent elongation. As the material properties of wood
are dependent on temperature and moisture content, a tradit ional method for extending the
plasticity of a number of hardwood species e.g., ash, beech, birch, elm and white oak, is
steaming. When the wood reaches moisture content close to the fiber saturation point, the
steam softens the wood fibers and allows them to distort in relation to each other (Keyser
1985). This increases the elongation abil ity in tension to approximately two percent and
the compressibil i ty to a signif icant 30 percent or more. Thus steaming allows extending the
range of possible curvatures considerably and, if the steaming time is l imited to the required
one to two minutes per mil l imeter thickness at approximately 100 to 110° C, the strength
losses do not exceed 20 percent (Hoadley 2000).
Tradit ionally, steam-bending processes require a mould that defines the curvature of the
part to be formed. This project, developed by Jeffrey Niemasz, Jon Sargent and Laura
Viklund (Performative Wood Studio, Prof. Achim Menges, Harvard GSD 2009), explored
ways of developing a computational design process that al lows the free forming of steamed
white-oak slats without the need for a 100 percent contact mould. In order to achieve this,
a large number of physical tests were conducted, investigating the process parameters of
steaming e.g. temperature, t ime (Figure 3a), the specif ication parameters of the slats such
as species, f iber direction, init ial moisture content, and thickness, in relation to the forming
figure (Figure 3b) that the slats f ind when the posit ion of one endpoint is translated in space
in relation to the other. The resultant data was used to set up a computational form-finding
tool for a multi layered latt ice system constructed from bent and twisted white oak slats.
The deve loped in tegra t i ve computa t iona l des ign too l was tes ted by const ruc t ing a
fu l l sca le p ro to type f rom more than 1000 geomet r ica l l y un ique par ts . The l igh twe ight
s t ruc tu re is computa t iona l l y der i ved as a doub le layered la t t ice prov id ing both a
77
Figure 5a. Kerfed oak
Figure 5b. Kerf forming
Figure 5c. Kerf variables
Figure 6a. Gradual kerf orientation/depth changes
(top) avoiding kinks (bottom)
Figure 6b. Bending behavior (top) of robot-sawn
gradual kerf depth (bottom)
Fig. 5a Fig. 5b
Fig. 5c
spat ia l d iv is ion and a seat ing sur face, in wh ich the th ickness o f s la ts , the number
o f layers and the depth o f the sys tem responds to the load-bear ing requ i rements
(F igure 4a) . Ut i l i z ing a custom-bu i l t s team chamber and a s imp le CNC-cut fo rmwork
tha t gu ides the f ree fo rming o f the s teamed p ieces by spat ia l re fe rence po in ts , the
pro to type was const ruc ted f rom wh i te oak s la ts w i thout any add i t iona l mechan ica l
fas teners o r f i x ings (F igures 4b/c) .
4.2 RESEARCH PROJECT 02: HYPERBOLOID STRUCTURE CONSTRUCTED FROM PRE-STRESSED
ROBOTICALLY KERFED WHITE OAK ELEMENTS
The nex t r esea rch p ro j ec t , deve l oped by B rad C rane , And rew McGee , Ma rsha l l
P r ado and Yang Zhao (Pe r f o rma t i ve Wood S tud io , P ro f . Ach im Menges , Ha r va rd
GSD 2010 ) , i n ves t i ga ted ways o f e x t end i ng t he poss ib i l i t y o f s t eamed , f r ee f o rmed
wooden s l a t s t h rough s t r a t eg i c accumu la t i ve l oca l weaken i ng and d i s r up t i on o f
f i be r con t i nu i t y by ke r f i ng ( F igu re 5a ) . The p ro j ec t a imed to deve lop an i n t eg ra ted
compu ta t i ona l des i gn t oo l and robo t i c manu fac tu r i ng p rocess t ha t a l l ows
p rog ramming t he bend ing and tw i s t i ng behav i o r ( F igu re 5b ) o f t ens i oned wood
e l emen ts t h rough spec i f i c ke r f i ng ( F igu re 5c ) .
Because o f wood ’s an i so t r op i c cha rac te r i s t i c s , ma te r i a l pe rpend icu l a r t o t he ma in
g r a i n d i r ec t i on can be r emoved w i t hou t ove r l y comprom is i ng t he ove ra l l s t r uc tu r a l
capac i t y. I n boa t cons t r uc t i on , f u r n i t u r e mak i ng and o the r f i e l ds , r egu l a r ke r f i ng
i s a we l l known t echn ique f o r f ab r i ca t i ng wooden pa r t s ben t i n one d i r ec t i on .
Th i s p ro j ec t e xp lo red how the compu te r con t r o l l ed va r i a t i on o f ke r f dep th , l eng th ,
f r equency and o r i en t a t i on a l l owed f o r ach i ev i ng mo re e l abo ra te bend ing and
wa rp i ng f i gu res .
Unde rs tood as a s ys tem o f cumu la t i ve ke r f s , t he mac ro -sca l e man ipu l a t i on o f t he
wooden s l a t s p r i o r t o s t eam ing mod i f i e s t he i r bend i ng behav i o r. Cons tan t ke r f
dep th r esu l t s i n s t r ess concen t r a t i on a t t he end o f ke r f ed l eng th , l ead i ng t o t he
i so l a t ed ac t i v a t i on o f t hese r eg i ons and consequen t l y p roduces k i nks a t t hese
po i n t s ( F igu re 6a ) . Howeve r, va r y i ng ke r f dep th g r adua l l y i n r e l a t i on t o t he s t r ess
d i s t r i bu t i on a l l ows f o r ca l i b r a t i ng t he bend ing s t i f f ness w i t h ma te r i a l r emova l . Fo r
e xamp le , i f t he dep th va r i a t i on o f pa ra l l e l ke r f s f o l l ows a s i ne cu r ve , t he r esu l t an t
f i gu re d i sp l a ys g r adua l cu r va tu re change avo id i ng s t r ess concen t r a t i ons o r k i n ks
( F igu re 6b ) . Robo t i c saw ing p rov i des t he r equ i r ed va r i ab i l i t y and p rec i s i on t o
i ns t r umen ta l i z e ke r f i ng i n t h i s way.
A cus tom-des igned ro t a r y saw too l f o r a 6 -ax i s r obo t ( F igu re 7a ) was cons t r uc ted
and enab l ed t he t es t i ng o f r e l a t ed p rocess pa rame te r s , e .g . , saw b l ade r evo l u t i on ,
f eed r a t e , c l imb cu t t i ng and conven t i ona l cu t t i ng , e t c . , i n r e l a t i on t o geome t r i c ke r f
pa rame te r s i nc l ud i ng ke r f dep th , l eng th , f r equency and o r i en t a t i on ( F igu re 7b ) .
The behav i o r a l cha rac te r i s t i c s o f t he r esu l t an t t es t p i eces ( F igu re 7c ) t oge the r
w i t h t he f ab r i ca t i on pa rame te r s we re i n t eg ra ted i n a compu ta t i ona l des i gn t oo l and
t es ted t h rough t he cons t r uc t i on o f a l a r ge r sca l e p ro to t ype .
As i n i t i a l t es t s had shown t ha t spec i f i c ke r f pa t t e r ns a l l ow f o r ach i ev i ng a
s ys tem-geome t r y w i t h nega t i ve Gauss i an geome t r y, once an assemb l y o f mu l t i p l e
ke r f ed e l emen ts i s p re -s t r essed , t he p ro to t ype was deve loped as an i r r egu l a r
h ype rbo lo i d g l oba l s ys tem cons i s t i ng o f mo re t han 140 e l emen ts w i t h un ique l oca l
ke r f pa t t e r ns ( F igu re 8a ) . Cond i t i on i ng t he phys i ca l f o rm ing behav i o r o f each
e l emen t , t he compu ta t i ona l des i gn t oo l gene ra tes t he i nd i v i dua l ke r f pa t t e r ns ,
p rov i des t he r e l e van t geome t r i c da t a and ou tpu t s t h i s d i r ec t l y i n r obo t con t r o l
code . Th i s enab l es t he d i r ec t f ab r i ca t i on o f t he i nd i v i dua l ke r f ed p i eces t ha t we re
subsequen t l y s t eamed , p re -s t r essed , assemb led i n t o componen ts and f i na l l y
assemb led as a 5 me te r t a l l h ype rbo lo i d p ro to t ype ( F igu res 8b /c ) .
4.3 RESEARCH PROJECT 03: BENDING-ACTIVE PAVILION CONSTRUCTED FROM ROBOTICALLY
FABRICATED AND ELASTICALLY BENT BIRCH PLYWOOD LAMELLAS
This research project conducted by the the Inst i tute for Computat ional Design (Prof. Achim
Menges) and the Inst i tute of Bui lding Structures and Structural Design (Prof. Jan Knippers)
Fig. 6a
Fig. 6b
computation, formation and materiality
78
integration through computationacadia 2011 _proceedings
Figure 7a. Robot-saw tool
Figure 7b. Robotic kerfing
Figure 7c. Variable kerfs
Figure 8a. Prototype
Figure 8b/c. Prototype structure and kerfing detail
Fig. 7a
Fig. 7b Fig. 7c
a imed a t fu r ther deve lop ing mater ia l -based computa t iona l des ign, eng i nee r i ng and
robo t i c manu fac tu r i ng o f e l as t i ca l l y ben t wooden s t r uc tu res . The r esu l t i s a nove l
p re -s t r essed s t r uc tu r a l s ys tem - he re r e f e r r ed t o as a bend ing -ac t i ve s t r uc tu re
( L i enha rd e t a l . 2010 ) - an i n t r i ca te ne two rk o f j o i n t po i n t s and r e l a t ed f o rce
vec to r s t ha t a r e spa t i a l l y med i a t ed by t he e l as t i c ma te r i a l behav i ou r o f t h i n b i r ch
p l ywood l ame l l a s , wh i ch was deve loped and subsequen t l y t es ted as a f u l l sca l e
r esea rch pav i l i on .
The bas i c p r i nc ip l e o f t h i s s ys tem i s t ha t t he i n i t i a l l y p l ana r p l ywood s t r i ps a re
manu fac tu red w i t h a 6 -ax i s i ndus t r i a l r obo t and subsequen t l y connec ted so t ha t
e l as t i ca l l y ben t and t ens i oned r eg i ons a l t e r na te a l ong t he i r l eng th . The f o rce
t ha t i s l oca l l y s t o red i n each ben t r eg i on o f t he s t r i p , and ma in t a i ned by t he
co r r espond ing t ens i oned r eg i on o f t he ne i ghbo r i ng s t r i p , g rea t l y i nc reases t he
s t r uc tu r a l capac i t y o f t he sys tem ( F igu re 9a ) . I n o rde r t o p reven t l oca l s t r ess
concen t r a t i ons as we l l a s t he ad j acency o f weak spo ts w i t h i n t he ove ra l l s ys tem,
t he l oca t i ons o f t he j o i n t s be tween connec ted s t r i ps need to osc i l l a t e a l ong t he
s t r uc tu re , r esu l t i ng i n a d i s t i nc t a r t i cu l a t i on o f t he enve l ope . Th i s compu ta t i ona l l y
gene ra ted , i r r egu l a r d i s t r i bu t i on o f l oca l j o i n t po i n t s ( F igu re 9b ) g rea t l y enhances
t he s t r uc tu r a l capac i t y o f t he g l oba l s ys tem, bu t a l so r equ i r es each pa r t t o be
geome t r i ca l l y un ique .
The des i gn o f t he p ro to t ype pav i l i on began w i t h t he deve lopmen t o f a compu ta t i ona l
des i gn t oo l . I n t h i s t oo l a l l r e l e van t ma te r i a l behav i o r a l cha rac te r i s t i c s a re
i n t eg ra ted as pa rame t r i c dependenc i es based on a l a rge numbe r o f phys i ca l
and compu ta t i ona l t es t s . These t es t s f ocused on measu r i ng t he de f l ec t i ons o f
e l as t i ca l l y ben t p l ywood s t r i ps i n r e l a t i on t o va r i ous spec i f i ca t i on pa rame te r s as
we l l a s t he ca l i b r a t i on and co r robo ra t i on o f t he r esu l t i ng da ta w i t h f i n i t e e l emen t
me thods ( FEM) ( F igu re 10a ) . Based on 6400 l i nes o f code , t he deve loped
i n t eg ra t i ve compu ta t i ona l t oo l gene ra tes poss ib l e s ys tem mo rpho log i es t oge the r
w i t h a l l r e l e van t geome t r i c i n f o rma t i on and d i r ec t l y ou tpu t s t he da ta r equ i r ed f o r
bo th subsequen t FEM s imu l a t i ons and t he manu fac tu r i ng w i t h a 6 -ax i s i ndus t r i a l
r obo t ( F igu re 10b ) .
Embedded i n t he compu ta t i ona l des i gn p rocess , t he FEM s imu l a t i ons we re used
to ca l cu l a t e t he ac tua l ma te r i a l behav i ou r unde r t he g i ven geome t r i c and phys i ca l
cond i t i ons wh i l e cons ide r i ng a l l ac t i ng f o rces and ma te r i a l l im i t a t i ons . I n o rde r t o
s imu l a t e t he i n t r i ca te g l oba l equ i l i b r i um o f l oca l l y s t o red ene rgy t ha t r esu l t s f r om
the bend ing o f each s t r i p , t he mode l needs t o beg i n w i t h t he p l ana r d i s t r i bu t i on
o f t he 80 s t r i ps ( F igu re 11a ) , f o l l owed by s imu l a t i ng t he e l as t i c bend ing and
subsequen t coup l i ng o f t he s t r i ps t o f o rm a comb ined se l f - s t ab i l i z i ng s t r uc tu re
( F igu re 11b ) . The FEM mode l a l l owed f o r ve r i f y i ng t he geome t r i ca l shape w i t h i n
p rede f i ned s t r ess l e ve l s and ma te r i a l capac i t y u t i l i z a t i on , as we l l a s ana l y z i ng t he
de fo rma t i ons and s t r ess d i s t r i bu t i ons unde r ex te rna l w i nd l oads .
I n add i t i on t o t he ma te r i a l behav i ou r, t he manu fac tu r i ng and assemb l y l og i cs we re
i n t eg ra ted i n t he compu ta t i ona l p rocess . Based on t he mach i ne cons t r a i n t s o f
t he 6 -ax i s f ab r i ca t i on r obo t t o be used ( F igu re 12a ) , t he t h r ee c r i t i ca l de t a i l s o f
t he sys tem we re deve loped : [ i ] t he shea r- r es i s t an t j o i n t f o r connec t i ng ad j acen t
s t r i ps , [ i i ] t he t ens i on puzz l e j o i n t t o connec t s t r i p segmen ts o f l im i t ed s tock
s i ze ( F igu re 12b ) , and [ i i i ] t he j o i n t be tween e l as t i c s t r i p and t he s t r uc tu r a l base
( F igu re 12c ) . The d i r ec t gene ra t i on o f a l l manu fac tu r i ng da ta a l l owed t he r ap id
f ab r i ca t i on o f 500 geome t r i ca l l y un ique pa r t s .
The assembly p rocess is s t ra igh t fo rward and qu ick to execute , w i th no need fo r
ex tens ive sca f fo ld ing or add i t iona l equ ipment , as the p lanar s t r ips s imp ly need to
be connected and then automat ica l l y f ind the i r spec i f ic shape (F igure 13a) . In o ther
words, the mater ia l i t se l f u l t imate ly computes the shape o f the pav i l ion (F igure 13b) .
The spa t i a l a r t i cu l a t i on and s t r uc tu r a l s ys tem i s based on a ha l f - t o r us shape .
De f i n i ng t he u rban edge o f t he s i t e , i t t ouches t he g round topog raphy t ha t
p rov i des sea t i ng oppo r t un i t i e s on t he s t r ee t f ac i ng co rne r. I n con t r as t t o t h i s , t he
t o rus s i de t ha t f aces t he pub l i c squa re i s l i f t ed f r om the g round to f o rm a f r ee -
Fig. 8a Fig. 8b
Fig. 8c
79
spann i ng open i ng . I n s i de , t he t o ro i da l space can neve r be pe rce i ved i n i t s en t i r e t y
( F igu re 14a ) , l ead i ng t o a su rp r i s i ng spa t i a l dep th t ha t i s f u r t he r enhanced by
t he sequence o f d i r ec t and i nd i r ec t i l l um ina t i on r esu l t i ng f r om the convex and
concave undu l a t i ons o f t he enve l ope . I n t he f i na l s ys tem, t he comb ina t i on o f t he
p re -s t r ess r esu l t i ng f r om the e l as t i c bend ing du r i ng t he assemb l y p rocess and
t he mo rpho log i ca l d i f f e r en t i a t i on o f t he j o i n t l oca t i ons enab l es a ve r y l i gh twe igh t
s ys tem. The en t i r e pav i l i on , w i t h a d i ame te r o f mo re t han twe l ve me te r s , can be
cons t r uc ted us i ng ex t r eme l y t h i n b i r ch p l ywood l ame l l a s w i t h a t h i ckness o f on l y
6 .5mm. Th i s ex t r eme l y t h i n and ma te r i a l l y e f f i c i en t s k i n se r ves s imu l t aneous l y
as t he l oad -bea r i ng s t r uc tu re as we l l a s t he l i gh t modu l a t i ng and r a i n p ro tec t i ng
enve l ope ( F igu re 14b ) f o r t he sem i - i n t e r i o r e x t ens i on o f t he pub l i c squa re .
Beyond the invest iga t ion o f the re la ted a rch i tec tu ra l qua l i t i es , the const ruc t ion o f the
research pro jec t a l lowed fo r ve r i f y ing the presented computa t iona l des ign approach
by compar ing the computa t iona l des ign mode l , the re la ted FEM mode l and the actua l
geomet r y o f the const ruc ted pav i l ion . In co l labora t ion w i th geodes ic eng ineers , the
pav i l ion , as const ruc ted on s i te , was repeated ly d ig i t i zed us ing fu l l sca le scann ing
and geodes ic measurement techn iques (F igure 15a) resu l t ing in po in t -c loud
dataset . These exact measurements and re la ted mode ls a l lowed fo r compar ing the
computa t iona l des ign mode l , the FEM s imu la t ion and the actua l l y bu i l t s t ruc tu re ,
showing on ly m inor dev ia t ions between the th ree datasets (F igure 15b) .
I n add i t i on , t he scann i ng enab l ed t he obse r va t i on o f t he pav i l i on ’s s t r uc tu r a l
pe r f o rmance ove r a l onge r t ime pe r i od by documen t i ng t he geome t r y changes
r esu l t i ng f r om the r e l a xa t i on and c reep i ng o f t he p l ywood s t r i ps . I n t he f u t u re t h i s
i n f o rma t i on can be used to ca l i b r a t e t he FEM s imu l a t i on and he lps t o p red i c t t he
l ong t e rm behav i o r o f e l as t i ca l l y ben t wood cons t r uc t i ons .
5 Conclusion
The t h ree r esea rch p ro j ec t s demons t r a t e how a syn thes i s o f ma te r i a l , f o rm and
pe r f o rmance i n i n t eg ra t i ve compu ta t i ona l des i gn p rocesses a l l ows f o r de r i v i ng
comp lex s t r uc tu res f r om uncomp l i ca ted ma te r i a l s ys tems , wh i ch a re bo th
econom ica l t o bu i l d and ma te r i a l l y e f f i c i en t , wh i l e a t t he same t ime p rov i d i ng
un ique a rch i t ec tu r a l oppo r t un i t i e s . Th i s becomes pa r t i cu l a r l y c l ea r i n t he l a s t
p ro j ec t : Compa r i ng t he r esu l t s o f t he gene ra t i ve compu ta t i ona l des i gn p rocess
w i t h FEM s imu l a t i ons and t he exac t measu remen t o f t he geome t r y t ha t t he ma te r i a l
“ compu ted ” on s i t e i nd i ca tes t ha t t he sugges ted i n t eg ra t i on o f des i gn compu ta t i on
and ma te r i a l i z a t i on i s no l onge r an i dea l i z ed goa l bu t a f eas ib l e p ropos i t i on .
Acknowledgements
The au tho r g r a t e f u l l y acknow ledges t he r esea rch wo rk o f a l l pa r t i c i pan t s i n t he
Pe r f o rma t i ve Wood s tud ios a t Ha r va rd GSD, and i n pa r t i cu l a r t he s i gn i f i can t
con t r i bu t i ons o f Je f f r e y N i emasz , Jon Sa rgen t , Lau ra V i k l und and B rad C rane ,
And rew McGee , Ma rsha l l P r ado , and Yang Zhao . I n add i t i on , t he au tho r t hanks
h i s co l l eague Jan Kn ippe rs and a l l ICD and I TKE r esea rche rs and s tuden ts who
pa r t i c i pa ted i n t he Resea rch Pav i l i on p ro j ec t a t S tu t t ga r t Un i ve r s i t y, i n pa r t i cu l a r
Mo r i t z F l e i schmann , S imon Sch l e i che r, Ch r i s t ophe r Robe l l e r, Ju l i an L i enha rd ,
D i ana D ’Souza , Ka ro l a D i e r i chs as we l l a s And reas E i senha rd t , Manue l Vo l l r a t h ,
K r i s t i ne Wäch te r, Thomas I r owe t z , O l i ve r Dav id K r i eg , Ádm i r Mahmu tov i c , Pe te r
Meschendö r f e r, Leopo ld Möh le r, M ichae l Pe l ze r and Kon rad Ze rbe .
Fig. 9b
Fig. 9a
Figure 9a. Two jointed plywood strips with
alternating tensioned/bent segments
Figure 9b. Computationally derived distribution of
joint points
Figure 10a. Phyical / FEM bending tests
Figure 10b. Computational model
Figure 11a. FEM planar strip layout
Figure 11b. Equilibrium state simulation
Fig. 10a
Fig. 10b
Fig. 11a Fig. 11b
computation, formation and materiality
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integration through computationacadia 2011 _proceedings
Figure 12a. Robotic strip fabrication
Figure 12b. Tension joint detail
Figure 12c. Base joint detail
Figure 13a. Assembly of pavilion
Figure 13b. Bent plywood strip pavilion
Fig. 12a
Fig. 12b
Fig. 12c
Fig. 13a
Fig. 13b
81
Figure 14a. Interior view of pavilion
Figure 14b. Exterior view of pavilion
Figure 15a. Scanning of pavilion
Figure 15b. Dataset comparison
Fig. 14a
Fig. 14b
Fig. 15a
Fig. 15b
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computation, formation and materiality
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