"An integral approach to Structure and Architecture"

8/7/2019 "An integral approach to Structure and Architecture"

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-.Hugh Dutton

AN INTEGRAL APPROACHTO STRUCTUREAND ARCHITECTURE

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PROFESSIONAL AND INDUSTRIAL TERRITORIES

Engineers design structure and architects design curtain walls. This professional defini-tian isrepeated on site, where structural trades (concrete. steel. etc.) and cladding trades(glass. aluminum cladding. etc.) work in their di crete territories. The building industryis organized around these distinctions between PfofesSions and trades to the extent thateveryone involved with a typical project assumes the standard procedure will hold: struc-ture isemployed for the single purpose of supporting the building. while cladding is anenvelope around the struc ure C O keep rain out. But this assumption is not as ingrainedas it may seem to these builders - historically, structure and cladding were not distinct.The facade ofa brick 01 " stone building was both a structural and waterproof skin. Astheconstruction industry developed and the building trades became more specialized, theuse of the weatherproof skin as structure became more and more rare.

This divisions exists for reasons of professional and industrial expediency. At thedesign level. each profession concentrates on specific and distinct aspects of the build-ing. Toavoid risks of legal responsibility, one does not encroach 011 tile field of the other.a precaution that also simplifies the analytical process of understanding the differentparts of a building.

At the industry level. trades are defined bymaterials and often whether these materi-als are structural or non-structural. Onsite, the issue of construction tolerances and finishquality again draws a line between visible cladding or finishes and non-visible structure.

Evensome ofthe most sophisticated recent work. such as the Pyramid at the LouvreinParis by I.M.Pei, is characterized by this fundamental separation. An aluminum frame forthe silicone glazing system isfixed coan independent steel frame. This leads to a doublingup of 'structure' - the main skeleron in steel and the cladding framing in aluminum -despite the expressed minimalist architectural intention of maximum transparency.

Yet. it is possible to merge glass and steel into a single structural surface. An exam-ple of design before the modern tendency of 'layering' professions and trades is theBicton Palm house. Where [he hundreds of small glass panes form a daring shell struc-ture with a delicate minimal steel frame and tiny glazing bars.


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AUTOBIOGRAPHICAL NOTE MVlweI". von, . .. on3 tc hl te :c l w Ol in ng In Pe tl " j( R , c e' s P an s o ffi ce . R FR .lmmt!d my OWl) aUlhH~e 'awlIrd d 'f l" !o lgn RFR ' s . . .. .O l le ;beg~n In IhaoE!>Bll 'r 1980swllh u t e nm l1um t3nUl l lJ rC{l f}oh ou se s i in t he La Villele Screnee MUS8ltJ fn and tdev&l~opec WHn nll~ny orber orejeets in end around Pens A.nu '\mg t~d a tl d ho hs ti 'C ap pc nnc h t o d a: $l gl l wa s t il e phscs-optJ,,,.of ~he Qilies frQm I he f ir st d ay s. o J t he r ir rn I he re :wa e u c u 'l lL .u fJ o f m l:


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Electronic computer modeling is an essentialtool in the design of complex structures. Today'scapacities in the engineering field. notably in thearea of nonlinear analysis, allow us to betterunderstand structural behavior, The nonlinearanalysis permits an almos t endless s er i es o f 'a na ly -ses of a structu re that takes into accou nt its grad-ual dimensional transformation under load. Theysimulate the redistribution of forces within astructure as it deforms. Traditionally, if a tensionmember in a structure went slack its presencewould be excluded from consideration. However.with nonlinear analysis. ifthe member is able toresist force after the structure has deformedunder the load, then its capacity is considered.COLUMBIA UNIV.EASITY LEANER HALLGLASS WALL A'N i) RAMPS - STRUCTURING",,'RCHIHCT'UAE - A SYNTIHSI SThis project is a demonstration that structureshould not only be conceived as the mosteconomic or efficient solution to an architecturalproblem; if thought of as a design element, struc-ture can address architectural objectives whileresisting loads. The design involves a total inte-gration of steel structure and structural glass.

The hub glass wall and its supporting rampsmake a transparent counterpoint in the compo-sition of the Lerner Student Centre building byarchitects Bernard Tsehumi and Gruzen Samtonof New York Its clearly visible steel structure anbglass surfaces act as a foil to the two masonryc1~d wings of the building on either side. 111estructure spans between these two blocks. andthe glass encloses the hub void between them.The articulation of the trusses and steel rampstructures expresses the activity and movementzone of the hub itself; these functional structuralcomponents - ramp wind beams, main trellistruss, suspension rods, and cantilever glass sup-port arms - all animate the space.

The inclined arrangement of the ramps andtruss is a logical consequence of the changein levels between the Broadway street level andthe main campus level. which is half a typicalfloor he.tght above itThe angular geometry of thisarrangement is carried through into the layoutof all of the components of the facade andthe ramps. The glass grid follows the incline ofthe ramps. as do all of the support arms andfixing brackets.

The inclined facade truss is a simple rriangu-I ated trellts beam with tubes as compressionmembers and rod ties as tension members. "This

truss partially supports the ral'llps.which are an intricate mesh tex-ture of plates assembled d iago-nally, 1111' inner edges of the ra mpsare suspended by a virtual plane ofinclined ties from another, muchheav le r tri angulated trellis truss atroof level . Bach of these structuralcom po neuts are transparent inone way or another. The glassplane. with its own inclined gridmatrix of joinrs, is fjxed to theramps with cantilever armsarranged as a series of 'x' pointspunctuating the elevation.11H! glass is used s t r uc rura l lywi thout glazing bars . J r is a lamina to oof clear toughened glass units. It isfixed to the end of am, supportsusing boltedconl1ections. Eachpanel supports its own dead weightand wind loads. TI,e absence of glaz-ing bars or mullions iscritical to tileclear reading of the composition ofstructural elements. A clear dtst inc-non is thus achieved between thesteel structu re and the pure trans-parent glass weatherproof surface.TIle glass is fixed using a system ofbolts tb at inca rpo rates a sphericalbearing in the head of the boltallowing a moment [Teeconnectionto the glass at its holes.

Walking surfaces on the rampsare also executed in glass. Tiley areInade from lamina ted tiles wi t h theupper sheet roughened and cov-ered in an anti-slip treatment. Adust of tiny glass beads is laid Oilth e tops u rfa ce a nd then flame d tovi t r i z y it to the sur face.

The design also addresses visualexpression of the critical functionaldetails . .which are carefully studiedand drawn to express each specificfunction, TIley are designed todemonstrate how they work.

E ach can tilev er arm ';{ consistsof two lower 'gravity' arms thatsupport the dead weight of theglass and 'wind' arms that supportthe wind loads only. The reason furthis configuration is to clarity theanalysis of how rile glass is to

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other Wilythan in the manner for which it isdesigned. Eachglass panel is simply and indepen-dently supported. and ally relative movementbetween the arms 01" between the ramps cannotbe transferred into the glass as a load. This con-cept is rigorously carried through to all of thedetails. In the case of the gravity alms, the glass issupported on cast brackets at their ends. One liteis suspended from the bracket and the other restson it. For the wind arms, the end bracket is used(0 fix a group of small articulated struts that canonly resist wind loads perpendicular to the glassplane. They are free to rotate in all other direc-nons. thereby guaranteeing tbat they cannotresist any forces in the plane of the glass, If. forexample, the upper ramp deflects downward with

I a crowd of people, the glass panel suspended fromit remains free to move downward slightly with-out pushing on the arm of the ramp below it.Thisprinciple is critical to t.he compositional idea,because it allows the glass to be fixed to eachramp independently and directly without any sec-ondary framing, as would probably have been thecase in a conventional glazing application.

The arms ale hung from the ramps witha system of adjustment turnbuckles for correctionof construction tolerances that can be achievedeven ifthe glass isin place, This allows for nile tun-

Iing that could be necessary after the whole systemhas settled due to the dead weight ofthe glass.

The castings themselves are also equipped'with adjustment devices for fine tuning correc-tions. and. in particular. angular correction tocompensate for differences in arm angles, Aspherical bearing at the core of each piece per-nuts a rotational capacity. These adjustmentdevices are also used to correct for a slight non-alignment of the ramp stope with the glass grid.which isthe result of the two mid-slope landingsrequired by the New York building codes. Thecastings are important components of thedesign. because they resolve in a single piece theconsequences of the geometric complexity. Thecasting process gives these key parts a uniqueidentity specific to this project and allows themto express in an almost sculptural form the reso-lution of the overall geometric composition at < 1small hand-sized scale.Inengineering terms. though the main com-ponents. with the exception of the tamps, aresimple and classic structural elements. theirmovements and interactiviry require careful

design to evaluate the interactivebehavior of the different compo-nents of the structure and. in par-ticular. the relative stiffness of thetwo different trusses and theramps that they support

Full volumetric analysis wasrequired to understand the com-plex geometry of the ramps them,selves and the structural capacityof the tight mesh ofsmall elementsofwhich they are made, The designis based on the idea that every pieceof steel is fully exploited for itsstructural capacity as well as itsrole as a support element for sec-ondary finishes or cladding itemssuch as handrails, glass supportarms, glass floor tiling, etc, There isno distinction between any 'pri-mary' and 'secondary' structure orframing: everything is 'primary.'Glassflooring can be paved directlyonto the main structure and has nosecondary framing,

Such an intricate interfacebetween what are traditionally dis-tinct trades requires a particularcantractual.arrangerne nt to ensurethat necessary coordination hap-pens smoothly, lndeed, the designdepends wholly 011 the success ofthese delicate interfaces to work.To help make this happen. thedesigners proposed that one con-tractor be globally responsible forall components in the glass walland steel ramp design. and that allof it be let under one single bidpackage. Given that this type ofwork was not at all common in theUnited States. and particularly inNewYork,competition outside theUnited States was recommended.AFrench firm. Eiffe!ConstructionsMeralliques. was selected as thewinning bidder. This firm is princi-pally a steel fabricator with consid-erable experience in structuralglass as well.

Complications arising from aEuropean steel company working

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effort and cooperation of all concerned. Beyondthe issue of standards there was also a profes-sional culture barrier to break. The tried andtested methods, practices, and contractualresponsibility conventions inone country's con-struction industry are very different from thosein another country.

OSAKA MARITIME MUSEUM AN DSOCIETE GENEHALE GLAZED STEEL DaM ES -STRUCTURAL SKI NSIn the cwo projects presented here, glass andsteel work together as two parts of a single sur-face. Both are spherical surfaces using a spiralingradial Lamella pattern for the steel frame. Ineach case, the design of steel details isspecificallyadapted to the glass surface it supports.

SOCIETEGENERALEThe new Societe Genera'fe bank headquarters atLa Defense in Paris by the architects Andraultand Parat consists of two towers rising from aforty meter high base plinth. The plinth containsthe main entrance hall with a full height cylin-drical atrium space opped by a thirty meterdiameter glass dome centrally situated betweenthe twin towers.

The stainles 5 steel structure consists of aseries of ribs spanning between a centralcom-pression ring and a perimeter ring beam. Thesteel ribs are triangular in section and vary indepth from 250 millimeter deep at the edge to100 millimeter deep at the centre. The crossovernodes are designed as bolted joints to permit fac-tory assembly and avoid welding on site withoutany visual thickening of the members.

Light falling on the polis hed stainless steelmembers, which are inverted isosceles triangles,would be reflected downward into the space andwould thereby not create shadows on the profileswhen viewed from below. Thus the structurewould appear light and not in silhouette againstthe sky. The glazing gasket system is applieddirectly to the upper 'base' of the triangles.

The structure would have been more efficientif circumferential members WeTI'added in com-plete rings at the crossover nodes, thus creating aperfect triangulated grid-shell dome. but it wasdecided that the fluidity of the spiraling ribswould have been compromised. so the rings wereleft out. This means that the ribs function as archmembers relying on their bending capacity to

ever, prevent the arches frombuckling sideways. allowing thedeep individual sections to be thinin plan.

The circumferential ring mem-bers would also have made glazingeasier, This is because it is not pos-sible to glaze the lozenge pane Iswith flat planes given the sphericalgeometry. The ring could haveprovided a glazing bar forming 3fold line, and the glass could beapplied inplanar triangular pan-els.Instead, the glass itself ismadein folded panels that are bentalong the circumferential lineforming twin triangular planes,and no joint is visible at all,

OSAKA MARITIME MUSEUMContrary to the Societe Generaleproject. the 73 meter diameterhemispherical Osaka MaritimeMuseum dome, designed witharchitect Paul Andreu, is a fully tri-angulated grid shell structurebraced by an 'x' of steel rods. This'x' also forms a point support forthe glazing. Four glass panels areused to clad each lozenge of thedome structure. At the mid pointof each, the rods Cl"OSS over and aglazing support bracket supportsthe internal corners of the foursheets of glass

The dome glazing bas a dou-ble role as necessary shading forthe internal volume in addition tokeeping the rain out. Osaka's cli-mate is relatively hot, and thegreenhouse effect of the entirelyglazed volume would have madeit intolerable for the users. Theglass is a laminate with a perfo-rated steel sheet incorporated inthe interlayer. The density of theperforations in the glass vary as afunction of the shading require-ments for the internal volume.The annual solar exposure of thedome is plotted as a contour mapprojected onto the dome surface.

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contour represents aperforation in the interlayer metal sheet, suchthat it is highly shaded at the top and moretranslucent towards the base where the sheetdisappears. Views of the surrounding seascapeare unhindered while the space is protectedfrom sunlight coming from above.

STRUCTURAL GLASSAn integrated approach to design involves a struc-tural exploitation of materials traditionally in thecladding domain, which requires a better under-standing of the behavior of.conventional claddingmaterials such as glass or sheet metal. Structureand skin become one and the same.

Rice's La Villette greenhouse facades witharchitect Adrien Fainsilber, one of the first pro-jects to use the glass itself to its full structural

, capacity, is a poignant example. The array ofroughened glass panels supports its self weightin each 8 meter x 8 me_ter bay, exploiting theglass's in-plane strength as well as each individ-ual panel's capacity to resist wind loads withoutany aluminum framing. The resulting curtain ofsixteen glass sheets is then braced using cabletrusses that support the only loads it is unable toresolve itself, which are the overall wind forces.

The structural glass advances at La Villettedepend all three principle technical achieve-men ts th at set ita part from tradi tional glass ;-vaIIdesign, First, the glass industry's innovation oftoughened glass, which improves its long term, performance and strength. Secondly, the develop-ment of nonlinear engineering analysis enablingthe use of pre-tressed cable wind trusses. Andthird, the development of special articulated glassbolt attachments that achieve a predictable per-formance of the glass, even though it is beingfixed to a relatively supple support system.

Glass panels can also be employed as pri-mary structural members. In this case, sufficientcare must taken in detailing the connections [0take into account its brittle nature and sensitiv-ity to cracking. Glass structures can be analyzedusing computer finite element modeling, wherethe material or object is recreated as anelectronic model simulating the material struc-rural properties.

The appearance of the structural glass con-nections becomes an explicit tactile expressionofthei r function. Beyond making the force linesthemselves readable, there is the aestheticpotential of the details for their own decorativevalue. The cast stainless steel structural glass

alization using computer graphicssoftware to refine their shape.Once the final shape is agreed on,then the models are used as a basisfor fabrication drawings and cast-ing mold fabrication.

T.CTON IC ARCHITeCTURALCOMPOS ITIONThe work reviewed here is orga-nized in a gradual progressionfrom large scale structures to struc-tural glass and its connections.From structure to structural skin.One might conclude that with suchan approach the total architecturalform and image ends up beingdetermined by purely structuralrequirements. However, this is notthe intent. On the contrary, it is topoint out the potential designbenefits when the various tech-nologies involved in building arefully understood and composed asa conscious whole.

An integral approach to designrequires a deep understanding ofthe technologies of architecture,We design with this technology. Itis a critical tool of our designmethodology. It is important to con-trol it as designers.

There is a danger as architec-tural technologies become so com-plex and difficult that it is impossi-ble for designers to master them. Itis important not to be over-whelmed. Architects work at thebeginning of the building processand can still remain in control atthe level of first principles. There isa risk in the profession's growingtendency to flee responsibility andreadiness to leave the resolutionof the detailed work to the contrac-tor . 111ismeans that we shall gradu-ally lose the required skills, andellen ts wlll go directly to buildersand engineers. In time thedesigner's role shall become lessand less significant.

a bo ve . l el t a nd ngtll: S O A V n u e M o nt 61 tJ n e Th e SYSTem deve l -o ped a I La V i I IL l .tc is a lso repeated o n a I Dr ge l scala o n t~(! 50AIo ' e nu f l 'MCn. l a i gM project i n t h e Q l a zc d euna In o j 9 6 p an els :o .g la s s. ] e m . .. ..ide by 2 4m il iO n

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"An integral approach to Structure and Architecture"