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The form of an object is a direct representation of the forces by which it has been subjected; forces both internal and external. As forms in nature, like those of the built environment, are subject both to the limitations of the materials strength and external forces such as gravity, lessons from nature are often applicable to the built environment, providing useful insights into new techniques for advancements in structural efficiency. The philosophy of biomimicry has significant potential in the structural realm, whereby rather than simply copying the forms of nature which can be problematic due scales of magnitude, the true profundities are believed to come from an improved understanding of how nature and its forms work. Orchids are the specific focus of this study as the diverse and varied forms often overcome external forces through a manipulation of form. To resist force through form, rather than ‘the awkward accumulation of matter,’ is the core by which structural efficiency is founded. The thesis provides a general overview into the aspects of; sustainability; biomimicry; structural efficiency; the developments and opportunities presented by material and computer-aided design advancements, as well as researching the forms developed by the great structural artists such as; Antoni Gaudi; Eduardo Torroja; Eladio Dieste and Felix Candella. A variety of orchid forms were selected and analysed, and the findings are presented as common structural techniques and forms seen throughout a number of the orchid species. It was found that many of the orchid forms share similarities with those of the structural artists, although the great diversity of forms presents new techniques which could have exciting implications on the next generation of structures.
Keywords: Biomimicry, Computer-Aided Design, Orchids, Structural Efficiency
Joshua Anthony O’Meara, Supervisor: Sambit Datta
Deakin University, Geelong, Australia
Sustainability is unequivocally the most pressing issue of our time. The recently emerging philosophy of biomimicry represents a highly plausible guideline for humanity to address sustainable development, through innovation, guided by wisdom. A guiding principle of biomimicry is the idea of ‘tapping the power of limits.’ This principle is pertinent for the purpose of this thesis, as this is also the core principle by which structural artists discover their genius. Furthermore, it is apparent that structures in nature, are subject to the same forces as the built environment, and thus the idea of applying the philosophy of biomimicry to structural innovation could provide great insight. Forms in nature are derived from the forces by which they are or have been subjected. In contrast, the built environment tends towards pre-determined forms such as flat planes, which due to their inefficiencies are compensated through mass or the addition of supporting members. In this regard, architect Antoni Gaudi was well before his time. Gaudi looked to nature as his mentor, and his building forms, like nature were derived from the forces acting upon them. Through the intelligent use of form, Gaudi provided resistance to the acting forces, subjecting his materials to high levels of force within their capabilities achieving great structural efficiency.
Structural efficiency is important not only economically, but is also critical in creating more sustainable designs. As evident in the work of Gaudi as well as other structural artists such as Torroja, Dieste and Candella, structurally efficient forms, in following the laws of nature tend to result in elegant and beautiful forms. This thesis, whilst not of a mathematical or technical nature, explores structural principles and the influence of form on structural efficiency. The thesis provides a general overview of sustainability, biomimicry, structural efficiency and the various innovations of the aforementioned masters. The research then explores the forms of nature, specifically orchids, to analyse their curves for structural merit, discovering new forms which could become applicable in the built environment. The success of structural artists relies on their development of economical solutions that are easily constructed, for example, through the use of straight-line generators. As computer-aided design and manufacturing continue to advance, the possibility of forms with greater complexity will be made increasingly feasible and therefore lessons from nature increasingly applicable.
- 1. SUSTAINABILITY AND THE ORIGINS OF BIOMIMICRY
Today sustainability is often used interchangeably with sustainable development, despite some critics such as David Pearce (Palmer: pp.87) arguing that the latter is an oxymoron. This alternate use between the two has no doubt affected the general understanding of the terms and has perhaps contributed to the meaning of sustainability being broadened. The most widely used definition for Sustainable development comes from Dr. Gro Harlem Brundtland, defined as “development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” This definition introduces the generality of sustainability, although remains rather vague and some assumptions must be made. Despite being weak the definition does introduces the first principle; futurity. Another principle recognised to have growing importance to sustainability is that of equity. In an age of nuclear armaments, the importance of peace is significant to both humanity and the future of the planet. The Friends of the Earth Scotland (Palmer: pp.90) recognise that in a finite planet, with finite resources, greater equity is pivotal to maintaining peace. The last principle; Public Participation came from the Rio Declaration on Environment and Development (UNCED, 1992) and recognises the fundamental necessity for all to be involved in our quest towards sustainability. The four principles recognised by Mitchell are intrinsically linked and are all critical in our path towards sustainability. Palmer has devised a scale, to aid people or organisations to make clear their position or understanding of the term, as to avoid miscommunication. For the purpose of this thesis, any reference to sustainability will be in regard to environmental management and environmental degradation as fig. 2 indicates the authors weighting. Whilst the author appreciates that these principles are all important and intrinsically linked, reference to equity and public participation will be made apparent through the use of alternate words.
[From the Greek bios, life, and mimesis, imitation]
- Nature as model. Biomimicry is a new science that studies nature’s models and then imitates or takes inspiration from these designs and processes to solve human problems, e.g., a solar cell inspired by a leaf.
- Nature as measure. Biomimicry uses an ecological standard to judge the “rightness” of our innovations. After 3.8 billion years of evolution, nature has learned: What works. What is appropriate. What lasts.
- Nature as mentor. Biomimicry is a new way of viewing and valuing nature. It introduces an era based not on what we can extract from the natural world, but on what we can learn from it.
(Benyus 1996: preface)
- 1. BIOMIMICRY AND THE BUILT ENVIRONMENT
2.1. The role of built environment and structural efficiency on sustainability
Benyus states that ‘organisms have evolved to work smarter, not harder (Benyus 1997: pp. 5), with their forms synonymous with their function and often further economised by combining one structure to serve multiple functions (Benyus 1997: pp. 265). The reason for nature using materials and energy sparingly, as Benyus explains is a matter of survival (Benyus 1997: pp. 5) whereby through the power of limits, nature ‘optimises rather than maximises’ (Benyus 1997: pp. 4). She highlights that species ‘build for durability, but they don’t overbuild’ and nature also benefits through the use of composite materials to gain strength rather than bulk (Benyus 1997: pp. 265).
What becomes retrospectively apparent as our knowledge of nature continues to expand is that many of mankind’s greatest innovations had already existed in nature in some regard. In fact, those by whom we hold the highest esteem for their contributions to human knowledge were often those who simply had the profound insight to understand the very workings of nature, for this is the basis of science. In architecture, Gaudi’s appreciation for geometry and engineering allowed him to quickly discover deeper profundities in nature, beyond the mere superficialities. He was thus able to express principles, rather than merely imitate nature’s effects.
Gaudi appreciated that through this torsion, helicoids gain strength and he therefore adopted the form to be used in many of his spiral staircases such as in the towers of the Sagrada Familia Cathedral as seen in Fig.5. Furthermore, the helicoid form is produced using ruled surfaces or from straight-lines generators and thus the form was economical and practical to construct. The use of ruled surfaces was a favoured practice of Gaudi and was also adopted widely by the structural artists who followed. As Timothy Becker highlights its use ‘not only imbues the vaults with grace but also creates forms on demand and with ease, with sound structural properties like those found in nature’ (Anderson 2004: pp. 206).
- STRUCTURAL EFFICIENCY
3.1. Definition and key developments
French states that ‘nearly always it is desirable to use as little materials as possible both for reasons of economy, which apply no less in nature than in human affairs, and also usually for functional reasons‘(1988: pp. 105). With two decades passed since this statement, one would certainly also add to the list, the benefits towards sustainability. Historically, it was prevalent for structures to function in compression with the use of mass materials such as stone, masonry and concrete. In Spain Catalan tiles were used to great effect, as one of the first major development towards light-weight structures. Catalan tiles are structurally effective by the manner in which the tiles overlap one another, thus acting as a shell and working as a whole, eliminating abrupt interfaces and potential weaknesses, a phenomenon found commonly in nature (French 1988, p.117). This material was used by Gaudi to great success, whereby he explored the implications of form on a structures ability to resist forces. With the advent of steel, a material which exhibits a great strength to weight ratio and impressive tensile strength characteristics, a new age in structural efficiency was born, allowing light-weight structures capable of spanning great distances. As the dead-load of a structure often accounts for a major aspect of the forces it must resist, lighter structures can provide clear advantages, often reducing both; the lateral thrusts; the vertical structure requirements and the size of footings. Garlock et al. (2009: pp.42) explains that enthusiasm for structural efficiency sprouted as ‘the spirit of rationality was popularised by Viollet-le-Duc giving it a theoretical justification. The innovation of the composite material; reinforced concrete was equally radical as that of steel, with steel and concrete in combination exhibiting greater capabilities then the materials are capable alone. Reinforced concrete with its ability to absorb tensile stresses due to the steel reinforcing and the plasticity that comes from concrete, allowed designer’s great new freedom in form.
Rowland Mainstone has developed three criteria he believes to be important in the development of new structural forms. These are as follows;
i. Intuitions of structural behaviour: a spatial awareness of stability and the geometry of structures, and a feel for the nature of the forces in a structure; a muscular, physical sense of structure.
ii. Intuitions of structural action: a more refined view of structural behaviour, the basis of the mathematical analysis of structure; the description of behaviour in the quantitative terms of forces and moments, stresses and strains
iii. Intuitions of structural adequacy: a quasi –empirical view of structures, based on experience and practise.
(Anderson, 2004: p.138)
The latter two are beyond the scope of this thesis, with intuitions of structural behaviour the primary focus for this work.
Materials commonly used in the past such as stone and masonry are poor in tension and therefore the arch which works in pure compression allowed these materials to span over spaces. The laws of physics permit that materials will seek equilibrium by finding their lowest point of resistance, and thus the arch due to the influence of gravity will create downward and lateral thrusts which need to be resisted for the arch to maintain its shape. If the lateral thrusts from the arch are not resisted, the funicular shape, which is the most efficient form for an arch will be lost and the form will act rather as a curved beam, taking on bending, which was absent in the funicular form (Torroja 1962: p.88) . A funicular curve is one which is exhibited by holding a chain at two ends. In the example of the chain the curve acts in tension. The arch is therefore this shape reversed curving towards the sky to act in compression. The catenary curve is most efficient funicular shape for an arch of equal thickness acting only under its dead weight (Torroja 1962: p.90) but as Torroja highlights heavier materials tend to demand higher curves as to reduce the magnitude of lateral thrusts which could become excessive (Torroja 1962: p.89). The lower the funicular profile of the curve, the higher the compressive forces and the greater the lateral thrusts. Traditionally lateral thrusts were absorbed by massive walls or buttresses or in the case of vaults which act like a series of arches, the vaults were often placed beside one another to counter one another’s thrusts. For Gaudi the addition of lateral supports was seen to be a structural flaw and he sought to discover an arch form which required no additional lateral support. His experimentations and use of graphic statics allowed him to align the thrusts with the supporting columns (Anderson 2004: p.71) and he was able to merge the columns seamlessly into the arch form developing what Descharnes et. al (1971: p.54) describe as an ‘oblique parabolic order’.
Like arches, the deadweight tends to produce the greatest stresses in shell structures, especially in roofing applications. Like arches a lighter profile therefore becomes beneficial to the structure as it must withstand less force and can therefore span greater distances. Garlock (2009) describes the remarkable phenomenon of shell structures, stating:
‘it may seem counterintuitive that thinner structures when properly formed can lead to surfaces with lower stresses, but this is a structural truth discovered in the late 1920s by Robert Maillart.’
Structural artists are those who have dedicated their working lives towards the pursuit of structural perfection. It is common as Anderson (2004: p.94) highlights for a structural artist to concentrate on one specific material and extend the materials known capabilities. Whilst the methodology of structural artist’s such as Gaudi, Torroja, Dieste and Candela varied, what they all shared was an intimate understanding of the construction processes, a sound understanding of structural behaviour and an artistic discrimination, which allowed their structures to be elevated to works of art. A view shared by Torroja, Dieste and Candela and earlier touched on by Mainstone’s three aspects of structural innovation is the importance in which intuition plays on the development of structurally efficient forms. Dieste for example, was quite critical of the education of engineers, whereby he believed students were exposed to mathematical formulas and computer modelling but failed to gain a true understanding of structural principles. As Torroja states;
Intuition, was particular emphasised by Candela whereby in his work he generally avoided complex calculations, favouring more simple formula supported by his sound understanding of the forces at work (Garlock et. Al 2009).
QUADRATIC RULED SURFACES
As earlier stated the use of ruled surfaces was a favourite practice of Gaudi. One of Gaudi’s best examples was the sinuous curved roof of the schoolhouse adjacent to Sagrada Familia as seen in Fig. 7. It is apparent that the structure had a great influence on Dieste as seen in figure.8. From the central beam of Gaudi’s roof outward the form was taken by Dieste for the walls in the Church of Christ the Workers, both adjusting the orientation of the line generators to create undulating parabolic curves. In both, the sinuous curves provide the forms with rigidity reducing bending by the deep profiles in the roof and providing lateral stiffness in Dieste’s walls. Ingeniously Dieste’s undulating wall follows as Ochsendorf highlights the ‘moment diagram for a pin-supported portal frame under its own weight and therefore provides for an efficient use of materials’ (Anderson, 2004: 98) as seen in Fig. 9. The undulations of walls to resist lateral thrusts were also used in Gaudi’s schoolhouse although his undulations remain vertical rather than tilting back and forth. The undulating walls cleverly align with the troughs and peaks of the roof structure to act as tympanum, which perhaps allow the forces to be spread more evenly across the roof surface rather than favouring the valleys.
Gaudi also used ruled surfaces also for the generation of hyperbolic paraboloids which was to be another form highly influential to his predecessors.
The material which Torroja focused much of his efforts was reinforced concrete. A major development by Torroja according to Garlock et. Al (2009: p.45) was the realisation of the connection ‘between the stresses in a shell and the reinforcing that needed to be placed in it.’ Torroja was thus able to create smooth shells not visually expressive of the forces. The freedom to add reinforcing locally and directionally, as well as the freedom to shape reinforced concrete to the desired form to resist the subjecting forces was an aspect that made the material especially favourable for Torroja. As Torroja comments ‘unlike rolled steel, concrete is not available in definite shapes listed in a catalogue; its forms and dimensions must be designed’ (Torroja, 1962: p.58) providing a designer with great freedom. Reinforced concretes ability both in compression and tension, also makes it economical for members which must resist both as ‘the system needs to be designed to withstand what the material is weakest’ (Thompson, 1917: p.676). One of Torroja’s most notable designs the Madrid Hippodrome as seen in Fig.10 and Fig.11, which adopts the hyperbolic paraboloid, a form used by Gaudi and was later extensively used by Candella.
Hyperbolic Parabaloids or Hypars are generated by two paraboloids intersecting perpendicular at their centre, with their curves facing opposite directions as seen in Fig.11, creating an arch in one direction and a cable in the other. A major advantage of hyperbolic paraboloids is that the complex double curving form is constructed from straight-line generators, allowing great economy in construction, whereby conventional straight boards can be used for formwork. As Candela concluded “of all the shapes we can give to the shell, the easiest and most practical to build is the hyperbolic paraboloid” (Garlock et. Al, p. 138). Furthermore, the double curvature provides great depth in form allowing hypars to be resistant to bending. With the cable acting in tension and the arch acting in compression (Anderson, 2004: p. 42) the opposing phenomenon’s work effectively together to maintain a stable form, providing stiffness as the two attempt to flatten against the resistance of the other. In Torroja’s Madrid Hippodrome as seen in Fig.12 he takes full advantage of this phenomenon allowing the cable to cantilever over the grandstand acting as a beam as the force is channelled to the vaults, while the arch takes the load to the columns. The way by which Torroja balances the structure is quite ingenious with the roof form extending not quite as far in opposite direction but balanced through a tie, which connects to the weight of the betting hall arch stabilising one another while the arch of the stand acts as a flying buttress to balance the whole structure. If one considers the Hyperbolic Paraboloid in elevation one will also notice that the depth of the form is widest in the centre where the two paraboloids cross. This together with the upward curve makes the form ideal for cantilevering, as the wider centre which takes the force continuously narrows as it cantilevers outward in the same manner as the recurrence found in a tree, following the pattern of bending moments. Torroja further enhanced this phenomenon by reducing the section of the structure as it approaches its end where forces from dead-weight are lowest.
Born in Uraguay, Eladio Dieste focused on the development of the use of reinforced brick masonry, a material locally available and economical in its use. Whilst masonry bricks are traditionally brittle and poor in tension and bending, through the use of reinforcing and pre-stressing and thus imposing a state of compression working to the materials strength, Dieste was able to use brick in new forms and to span vast distances.
The Gaussian vault was developed from Dieste’s appreciation of how an arch is affected by bending. As Torroja (1962: p.167) states ‘bending stresses diminish and finally vanish in the proximity of articulations, yet increase in the intermediate zones.’ Aware of this phenomenon Dieste developed the Gaussian vault, relating the shells form precisely with the bending forces where the risks of buckling are highest. He achieved this form by increasing the depth of the section most at the spans centre through the use of double curvature and diminishing it to become flat as it approaches the articulations or wall. As Dieste states ‘it is to some exemplary individuals that we turn to renew our enthusiasm for inventions that are complex yet, once realized, possess a simplicity and seeming inevitability – for inventions that are not mere novelties’ (Anderson, 2004: p. 183), the Gaussian vault is certainly one of those ingenious discoveries. The Gaussian vault is made up of catenary curves working essentially as a ‘shallow barrel vault that acts entirely in compression’ (Anderson, 2004: p. 75) and thus does not require pre-stressing (Anderson, 2004: p. 144). What makes the vault unique is that the catenary curves are of varying rise, creating in cross-section an s-shaped band as seen in Fig.14. This s-shaped profile exhibits double curvature providing the necessary stiffness to resist buckling and thus allowing great spans with thin shells, his largest 180 feet (Anderson, 2004: p. 75). The form is highly practical both in its relation to the forces it must resist, but also, the repetitive use of the Gaussian form allowed the formwork to be re-used for the entire structure, making its construction economical. Furthermore, the highest catenary curve which rests above the lowest curve provides a welcome opening, allowing natural light to penetrate the interior. The form becoming flat at its junctions also makes the articulations between roof and wall simple. One aspect which no doubt would have displeased Dieste, was the need for steel ties to resist the lateral thrusts which as earlier highlighted can be large in long shallow vaults. As used in Gaudi’s schoolhouse undulating walls could provide a solution to resist the lateral thrusts although the complexity would increase significantly inevitably adding to the construction costs. The wall undulations could align with those of the roof to provide an elegant junction although special consideration would be required in regard to re-using the formwork. Dieste would have undoubtedly considered the many alternatives and whilst more elegant solutions are possible, the Gaussian vault was most successful for its economic credentials, being most widely used in factory applications. The tie is an economical solution although in the eyes of structural artists it is a flaw.
As a student Felix Candela was often disheartened by the mathematical complexity associated with the forms he so admired (p. 65). The greatest influence on his work, according to Garlock et. Al. (2009: p. 64) was Robert Maillart who ‘encouraged simplified calculations rather than rigorous analysis.’ This was to become the foundation for Candella’s work. Candella realised that to pursue his interest in form he would need to establish his own construction practice. Candela therefore developed his ideas and intuitive abilities through practice where his prodigious roofing around Mexico gave him some freedom for experimentation. Like Torroja, reinforced concrete was the predominant material used Candella.
Whilst taking inspiration from a sketch by Aimond, Candela was the first to construct the Umbrella form (Garlock et. Al. 2009: p.98). The umbrella is created by joining four straight-edged hypar surfaces as seen in Fig.15. As small hyperbolic paraboloids the stresses remain similar although the arrangement directs the forces into the groins and the cantilevering effect of the form creates tension at the outer edges as indicated by the arrows in Fig. These forces can be resisted through additional steel reinforcement or the use of small edge beams and Candela often thickened the valleys. (Garlock et. Al, 2009: p. 99).
Folded hypars are Candela’s adaptation of an Umbrella whereby in the words of Candella two tympans are joined “in such a way that one short edge of each hypar is horizontal to the opposite short edge of the vertical” (Garlock et. al, 2009: p. 122). The result is a form that shifts from a vertical orientation until it becomes horizontal as it cantilevers outward as seen in Fig.17. The twisting orientation alludes to an overall expansion of form creating a dramatic structure which appears to defy gravity, exaggerated from certain perspectives as seen in Fig.18. The folded hypar was not widely used by Candela in comparison to umbrellas, as the formwork and drainage is more difficult (Garlock et. al, 2009:p. 122), restricting its use predominantly for sculptural purposes or dramatic roof features as was used in La Candelaria subway station, Mexico. Despite horizontal planes being inefficient against bending, the momentary horizontality, seen in folded hypars, is made possible as the dead weight and therefore subjecting forces become reduced as the shell extends outwards. The horizontal orientation therefore carries only the forces from its own weight and benefits from the stiffness provided by the forms overall torsion. Horizontal only at the forms edge, it immediately begins to shift vertically in accordance with the increasing bending forces. As seen in Fig. 17, in elevation the folded hypar is in fact a direct representation of a bending moments diagram for a cantilevered beam, the forces by which the folded hypar assumes. The forces are directed to the valleys and the form becomes increasingly deep in section adopting the form of recurrence, efficiently shaping upward. As Garlock (2009: p. 123) states Candela ‘found that the stresses in the main body of the shell were negligible, and that the valley and the reinforcing steel at the support could be sized using the cantilever method.
Los Manantiales Restaurant at Xochimilco is one of Candela’s most notable buildings and was the first groined vault attempted to intersect four hypars. In a groined vault, forces travel to the groins and are directed to the supports. Candella therefore thickened the groin sections and designed them to curve to provide continuity of the overall curved form.
- 1. BIOMIMICRY OF ORCHIDS
4.1. Why Orchids?
Orchids come in a multitude of forms despite the imposed limitations of their material properties, indicative of the power of limits. Orchids are often beautiful and through their forms, elegantly span across space, often seemingly defiant to the effects of gravity. Whilst undoubtedly benefiting from their light profiles, in consideration of the scales of magnitude, the relationship between material strength to span is likely to be similar to structures in the built environment. Whilst orchids remain in fluctuation from growth to death, for a period of time they hold their form more or less in a static equilibrium, indicative of structural integrity. Many of the forms and techniques used by structural artists are evident in the forms of orchids as well as a number of unique forms and techniques not common in the built environment. Whilst orchid forms are not restricted by a need for practicality in construction, which is a critical consideration for structural artists, advancements in CAD and CAM technologies provide new possibilities to creating increasingly complex and organic forms. Orchids therefore represent plausible models in structural form.
- 1. METHODOLOGY
Whilst the potential for such technology is exciting, it was found that the complexity of the orchid forms, at present precedes the capabilities of the machine in question and the ambitions of the author. A major limitation of the technology is its inability to scan concave surfaces, which are common in the forms of orchids. It is also beyond the capabilities of the fixed laser beam to recognise surfaces that are blocked in both directions by other surfaces in relation to the laser beams axis. In the three-dimensional double-curvature of orchid forms, this was a common occurrence. To attempt to overcome this, the orchids were fixed to a stand and positioned upright to expose the greatest amount of their surface perpendicular to the laser beam. Outcomes were improved, although the stand itself often interfered with the scanning. Furthermore, being held by the stand, the orchids were less secured and movements during the scanning process interfered with the accuracy of data collection. The laser was also lost in darker surfaces where the beam is absorbed and thus no data is registered.
This experience highlights the role in which technology has to play, although it provides caution, as while the potential for such technology is evident, whilst in its infant stages, technologies can remain temperamental. The irratic scans demand a revision of the research scope, whereby greater emphasis will need to come from general observations and analysis from photographs.
Despite the great variety of forms, common structural techniques were found amongst the different orchid species. The first technique which is seen regularly is the use of double curvature, adopting similar forms to that of the hyperbolic paraboloid, with the use of an intersecting arch and cable. This sound structural arrangement forms the basis by which diversity springs, with species adjusting the degrees of curvatures and size of petals. This can be seen in Fig. 22. The Arachnis hookeriana for example, due to its sporadic orientation, adopts a fierce inward curvature, establishing cylindrical like sections. With a section consistent in all directions, cylinders provide an efficient form for beams subject to bending from varied orientations. It is also common for the double curvature of orchids to exhibit a degree of torsion, or triple curvature, to realign the efficient double curvature form against the forces of gravity, thereby maintaining equilibrium.
This technique is seen again in the Labellum of many orchids, such as the Cymbidium, as can be seen in Fig. 23. Whilst adopting the double curvature with great effect, the Cymbidium labellum introduces a form not seen in the built environment. The curvature in section has an element of rectilinearity not seen than the conventional hyperbolic paraboloid, as can be observed in the Fig. 24 illustration. The cable is quite pronounced in its verticality providing the labellum with a deep overall section allowing it to resist bending and cantilever outward. The cable in fact, turns inward at its height. This technique provides additional stiffness to the form, acting in a similar manner to perhaps that of an edge beam. The cables more rectilinear form whilst less efficient is in fact quite deliberate and ingenious, as will be explained. Another aspect not seen in the hyperbolic paraboloids of the built environment is the use of internal ribs as seen in Fig 24. These internal beams act as reinforcement to the relatively flat base, which would otherwise be inefficient to the resist bending. When force is applied downward to the lip of the labellum the stiff reinforced base remains structurally stable whilst the weaker surrounds distribute the stresses up the cable walls. The rather square transition from arch to cable is a weakness in the labellum form and this weakness acts as a hinge, whereby the inward curving cable, already naturally inclined by its curvature bends further inward to absorb the stresses. As can be seen in Fig. 25 the labellum form uses hinges both at its articulation and later as the form breaks from its horizontal projection to hang vertically, eliminating bending stresses by balancing the remainder of the mass in equilibrium rather than cantilevering. The hinge at the labellum’s articulation works in unison with the cables inclination to curve inward, for when forces are applied to the lip, the hinge initially provides some flexibility reducing undue stresses on the overall form. The hinge flexed to its relative capacity, forces begin to accumulate and the cable wall is stressed turning further inward. The cables ‘edge beams’ catch on the column, which as seen in Fig. 24 has a form shaped for this very purpose. The column aligned directly from the stem is robust in its materiality and strength and therefore supports the labellum against momentary live loads, which otherwise could destroy the labellum and jeopardise the species reproduction. As can also be seen in the elevation in Fig. 25 the arch curvature is broken by a momentary hump, which is an inverse dome. The dome commences at the completion of the internal beam, where the arch in its totality ends and where the reversed curvature of the dome extends the form further outward. When force is applied to the underside of the inversed dome, the effect is for the orchid form to open outwards. As this force is not one that the dome would naturally experience, its influence to the overall form is indicative of the movement through its manipulation. The inversed dome maintains the forms overall compactness, inward emphasis and overall stability. The use of dome like forms is the second prevalent technique used by orchids.
In conclusion, we are at a critical moment in history, whereby sustainability is rapidly becoming a matter of human survival. Biomimicry appears as a highly plausible guideline whereby inspiration from nature could provide humanity with the framework for more intelligent design. The built environment, a major influence on sustainability, must play a critical role and developments in structural efficiency provide enormous scope for significant improvements. Biomimicry has long inspired architects and engineers and with CAD and CAM technologies advancing steadily, the next generation of organic, structurally efficient forms devised from the forces the building is subjected is upon us. Structural artists as well as the diverse orchid forms are terrific examples of the ‘power to tap limits.’ Orchid forms provide many significant lessons in structural efficiency and as building requirements continue to change many of the unique techniques could become increasingly appropriate for the built environment.
Orchid forms represent a wealth of knowledge for the structural design community. Orchid forms tend to have less precision than those of the built environment, therefore the scope for lessons to be taken, refined and applied are considerable. It would be worthwhile for the study of orchid forms to continue. As orchids are seasonal a longer period of study would be useful. Analysis of the forms structure through complex engineering software would be the logical next step. Lastly, the study of nature’s forms for lesson in structural efficiency should continue to broaden its scope, well beyond that of orchid forms.
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This Thesis is also published in The Enlightened Capitalist