Spatial, Structural, Skin Continuity
Rebecca Warren Yifang Yin (Cindy) Zhenghong Pan (Forest)
CONTENTS PART 1. CASE STUDY: DOWNLAND GRIDSHELL 1.1 Double Skin 1.2 Nature as an Envelope 1.3 Spatial Continuity 1.4 Structural Expression 1.5 Analysis
PART 2. TOUCHSTONE 2.1 Research 2.2 Matrices 2.3 Mobius Strip Models 2.4 Joint Exploration 2.5 Digital Model Progression 2.6 Trop Recipe 2.7 Touchstone Prototype 1 2.8 Future Development 2.9 Machine 1 - The Bending Box 2.10 Machine 2 - The Steam Box 2.11 Touchstone Prototype 2 2.12 Final Touchstone
PART 3. SPATIAL ORGANISATION 3.1 Site Context 3.2 Craft Victoria 3.3 Public vs. Private 3.4 Building Program 3.5 Spatial Model Prototype Development 3.6 Composition and Circulation 3.7 Spatial Model Prototype 3.8 Volumes Defined by Circulation 3.9 Floor Plates and Connections 3.10 Building Schematics 3.11 Final Spatial Model PART 4. CULTURAL MODEL 4.1 Subframe Treatment 4.2 Cultural Model Prototype 1 4.3 Subframe Treatment 2 4.4 Interior Circulation 4.5 Construction Section PART 5. FACADE PROTOTYPE 5.1 Final Model Forming Diagram 5.2 Urban Axonometric 5.3 Sectional Axonometric 5.4 Construction Sequence 5.5 Laminated Interior 5.6 Final Model Construction 5.7 Site Perspective 5.8 Building Perspective 5.9 Interior Rendering
PART 6. ESSAY Bibliography Attribution Matrix
PART 1. CASE STUDY: DOWNLAND GRIDSHELL
1.1 Double Skin 1.2 Nature as an Envelope 1.3 Spatial Continuity 1.4 Structural Expression
Introduction The Downland Gridshell by Edward Cullinan Architects is part of the Weald & Downland Museum in West Sussex, England. Located in the South Downs National Park, the Downland Gridshell building is predominantly surrounded by nature. The building is made up timber, shingles, glass and concrete. The most prominent feature of this building is the green oak lattice that forms the undulating gridshell. Downland Gridshell, Edward Cullinan Architects, 2002
Nature as an Envelope
Steel Window Frame
The Real Model
Downland Gridshell By Edward Cullinan Architects Glass Panel
Double Layor Green Oak Grid fixed by special Joints
The Inside Gridshell Made by Green Oak
Details on the Gridshell
The Jointing System
The Decomposed Model Showing the materiality of the project
Clamps and Dowels
Inside Beams for Bracing purpose
Edge Beams for supporting purpose
Analysis of Case Study The Downland Gridshell building conveys three core themes which are: - CONTINUITY - JOINTING - THE DOUBLE SKIN The building itself in its basic form is made up of a series of spherical volumes. By applying the green oak frame, shingles and glass over these volumes a sense of fluidity, leading to this idea of continuity. Furthermore, part of the building is concealed by an earth mound which is essentially acting like a plinth for the top public areas (within the gridshell). From this it almost appears as though the nature is continuing onto the structure itself. The jointing is crucial to this buildingâ€™s success. A simple joint consisting of three plates, bolts and screws brings the double timber lattice together to form the curving gridshell. This allows for a double skin to be implemented. The shingles and glass are then able to be fastened to the exterior creating two layers, hence resulting in a double skin. The notion of nature acting as an envelope is also notceable in this precendent study. With these in mind we looked to apply these ideas to our touchstone.
PART 2. TOUCHSTONE DEVELOPMENT
2.1 Research 2.2 Matrices 2.3 Mobius Strip Models 2.4 Joint Exploration 2.5 Digital Model Progression 2.6 Trop Recipe 2.7 Construction Process & Touchstone Prototype 1 2.8 Machine 1 - The Bending Box 2.9 Machine 2 - The Steam Box 2.10 Touchstone Prototype 2 2.11 Final Touchstone
(Surface and Volume Continuity)
Unorientable Surfaces Bisecting Volumes Continuity
Sculptures in S3, Saul Schleimer and Henry Segerman (Bridges 2012)
Multiply Scale Rotate
Interior Sculpture, Erwin Hauer Perforated Surfaces (http://www.tumblr.com/tagged/ erwin%20hauer?language=nl_NL)
Research (Mathematical and Structual
The Klein Bottle
Manipulating Mobius Surfaces and Mathematical Functions
Sculptures in S3, Saul Schleimer and Henry Segerman (Bridges, 2012)
The Downland Gridshell
Downland Gridshell, Edward Cullinan Architects, 2002
Matrices (Transforming Mobius Strip from set of regular points)
(Transforming Mobius Strip from set of irregular points)
SHIFT & OFFSET
‘NEEDLE AND THREAD’
Physical Mobius Strip Test Models
Using acetate, a series of mobius strips were joined together and rotated about a point. We found that acetate was not a suitable material for perpendicular jointing due to its flexible nature. From this experiement we started to see the emergence of certain qualities. There is a sense of the object being non-orientable, this is further accentuated by the transparency of the material. There are areas where the acetate is overlapping and twisting. Lastly, the mobius strips have come together to form a single volume.
This model looks at combining mobius strip bundles made out of acetate and paper. It expands on many of the qualities found in the previous acetate model. Overlapping and twisting moments are more apparent. There are also two volumes starting to take form. From these test models we realised the importance of material selection. Some flexibility is needed in order to achieve this type of curvature. There also needs to be a degree of stiffness so that the material retains its new shape and for jointing purposes.
Digital Touchstone Tests
Digital Touchstone Model Progression
Normal Mobius Strip
Analysize the iteration from section
Klein Surface 23
Digital Touchstone Model Progression 2D Rotating and Scaling:
Rotating and Scaling along vertical axis
Rotating and Scaling along horizontal axis
Touchstone Prototype 1
2D Rotating and Scaling in different planes
Multiply Scale Rotate
Touchstone Prototype 2 3D Rotating and Scaling in different planes
Touchstone Prototype 1 Model Testing Key concepts that our touchstone prototype 1 starts to address are: - Continuity - A non-orientable surface - Two distinct volumes - Emergence of jointing - Twisting moments - Overlapping points - Formation of open and closed spaces We felt that this prototype only really started to touch on these ideas, thus further refinement was needed. We began to look at the possibility of using other materials such as timber or metal. We also wanted to remove the need for a frame and to find a way to make the strips more continuous.
Touchstone Prototype 2
Our second touchstone iteration began to resolve some of the ideas and issues that were highlighted in our first touchstone attempt. Firstly, it is made entirely of 2.7mm plywood strips, this seemed to be more appropriate given that timber is predominantly used in our case study. In this model we successfully created a self standing object that really starts to explore the ideas of continuity, perpendicular jointing and twisting moments. Furthermore, there are still two central volumes, but unlike the previous model, one volume consists of open spaces, whilst the other is closed and more cave-like in appearance. During the making process we found it difficult to bend the smaller plywood strips, we experienced problems of breaking and we noticed that â€˜kinksâ€™ developed along the strips where they had been bent. We also realised upon completion that there was no true logic to our joining method where the pieces overlapped each other. This would explain why we struggled to get the pieces to stick together as we were forcing the material to join in such way that was not natural. Thus, for our final touchstone we felt that it was important to create a logical joining system to prevent a similar scenario happening again. From this we decided to proceed ahead with the final touchstone using a thinner material. We considered modelling ply and timber veneer. In the end we proceeded with Tasmanian Oak veneer with a thickness of 1.5mm.
Machine 1 - The Bending Box
The location of the plywood strips is adjustable. This means curves of different diameters can be produced.
Plywood strips were soaked in water overnight. Upon removal they were found to have some flexibility, but they were difficult to slot into the frame and bend into shape. Also, plywood strips that were bent into smaller diameters tended to be more prone breaking. Overall this method was quite time consuming and whilst it was able to manipulate the timber to certain extent it was not particularly effective.
Machine 2 - The Steam Box
Timber strips slotted in
Made up of 12mm thick plywood planks the steam box worked best in the vertical position. Strips needed to be steamed for at least 10 minutes in order for them to be successfully bent into shape.
Findings: - Open and closed spaces varying in size and orientation. - Cave-like volumes, both spacious and closed - Twisting moments about joints -Perpendicular jointing - Overlapping - Continuity
3.1 Site Context
3.2 Craft Victoria
3.3 Public vs. Private
3.4 Building Program
3.5 Spatial Model Prototype Development
3.6 Composition and Circulation
3.7 Spatial Model Prototype
3.8 Volumes Defined by Circulation
3.9 Floor Plates and Connections
3.10 Building Schematics
3.11 Final Spatial Model
Craft Victoria acts as a focal point for contemporary arts and crafts in the Melbourne area. It covers a wide range of disciplines such as sculpture, architecture and sound crafts. Thus, it provides artists and designers alike with a suitable place to showcase their work. Our building looks to address Craft Victoria’s needs by doing the following:
Financially Sustainable: - Comprehensive building program. - Logical progression through the building. - The ramps and stairs connecting the different spaces are to be used for exhibiting artworks. - Structure made out of inexpensive local timber. - Controlled movement ensures visitors move through to revenue generating areas such as the café and shop. - Outdoor seating to entice people to Crafts Victoria.
Craft Sustainability: - It’s eye catching form marks the start of the art precinct. - The building façade flows out into the landscape thus creating intrigue. This will act to bring people to the building. - Crafted outdoor furniture based on our façade design reinforces this idea of craft sustainability. - Lighting effects at night will be done in such a way to further entice people into the building.
Façade as a Leading Craft: - By using a known process of bending wood the intention is to convey the idea that the façade is something that could physically be handmade at a smaller scale. The façade is not about defining the building boundary, but rather it is to be viewed as a work of art in its own right. - Double skin approach makes this design stand out compared to the surrounding buildings. - Dynamic structure which conveys a sense of fluidity.
Public & Private
Spatial Relationship Analysis Diagram
Spatial Relationship Analysis Diagram
Spatial Arrangement Reasons
Spatial Model Prototype Development
Spatial Composition and Circulaiton
Spatial Model Prototype (ideas inspired from Klein Bottle)
Spatial Model Prototype (Physical model testing)
Volumes Defined by Circulation
Floor Plates Generated from Volumes
Final Spatial Organization
Final Spatial Model
Spatial Orgainization diagram
Spatial Orgainization diagram with floor and ramps
Final Physical Spatial Model
PART 4. CULTURAL MODEL
4.1 Subframe Treatment 1
4.2 Cultural Model Prototype 1
Subframe Treatment 1
Culture Model Prototype
The ramps from the spatial model informed the surface treatment of the cultural model. The intent of this was to create an undulating surface using veneer strips. The strip placement was informed by the ideas of twisting and overlapping. This leads to the development of a dynamic surface.
PART 5. Final Model
5.1 Final Model Forming Diagram
5.2 Urban Axonometric 5.3 Sectional Axonometric 5.4 Construction Sequence 5.5 Laminated Interior 5.6 Final Model Construction 5.7 Site Perspective 5.8 Building Perspective 5.9 Interior Rendering
Final Model Forming Diagram
Urban Axonometric 60
Sectional Axonometric 61
Sectional Axonometric 62
GLULAM STRUCTURE EAST-WEST
ETHYLENE TETRAFLUOROETHYLENE (ETFE)
GLULAM STRUCTURE NORTH-SOUTH
PRIMARY GLULAM STRUCTURE E-W
PRIMARY GLULAM STRUCTURE S-N EAST
5m FLOOR PLATES
STRUCTURE DIAGRAM NAILED HARD WOOD FLOOR INSULATION TIMBER FLOOR JOIST
GROUND FLOOR CONCRETE SLAB
Construction Sequence 63
NAILED WOOD FURNITURE
NAILED WOOD FLOOR
Laminated Interior 64
Final Model Construction In terms of construction, our final model utilised slot joints to tie the whole structure together. Due to material constraints and human error some of these joints did not work properly. However, the model was still able to be put together. If further developed jointing would need to be resolved and there needs to be a better, sturdier structural framework. Regardless of these problems we feel that we still have managed to convey some of our key concepts such as overlapping, twisting moments and continuity. However, the continuity would better conveyed if the entrance conditions were more developed.
Final Rendering view from Flinders St.
Interior Rendering view from Foyer 73
PART 6. Essay
Continuity Structural Treatment Jointing
RELATIONSHIP WITH CONTINUITY The Downland Gridshell strongly conveys the idea of spatial continuity. The building itself is defined by five spherical volumes set out in a linear fashion. The structural timber lattice follows these volumes to create an undulating surface, thus creating a sense of fluidity. The exterior treatment involves overlapping shingles, glass and concrete panels, giving the faรงade the appearance of being constructed out of long continuous strips. By having such a dynamic structure it is not possible to discern the start from the end. From this it can be established that there is a distinct relationship between continuity and the formation of a non-orientable structure. These two core concepts form the basis of our project. In order to understand how to create a continuous, non-orientable form it is necessary to look at two fundamental examples: the mobius strip and the Klein bottle. From this certain qualities can be ascertained. Firstly, there is some kind of twisting action whereby the start finds a way to meet the end. Secondly, curvature is required. Lastly, volumes have a tendency to intersect with each other to form new spaces. By applying this same logic it is possible to represent this in a built form. An example of this is the ContemPLAY Pavilion by DRS and FARMM in Montreal (Arch Daily, 2012). This dynamic, twisting structure is essentially two distorted mobius surfaces joined together (refer to figure 1). Furthermore, this pavilion is predominantly made up of timber slats and some of these have been curved to allow for the twisting moments within the structure. It is important to point out the curvature implemented is rather subtle, but the structure is still highly expressive. The ContemPLAY pavilion hints at the potential of timber as a bending material. By adding more curvature to the framework it would be possible to create a more dynamic structure that would further reinforce the idea of a continuous, non-orientable surface.
Figure 1, ContemPLAY Pavilion, (Arch Daily, 2012)
Figure 2, Boat Construction, (Surfbird, 2013)
To be able to even start exploring this notion, various things needed to be taken into consideration including the method of bending and the type of timber used. Generally the most common method for bending wood is to first steam it and then use some kind of device to shape it. Other methods can be used such as immersing the timber in a hot water bath or treating it with chemicals (State Forests of New South Wales, 1995). For our project inspiration was directly drawn from kayak and boat making practices. An example can be seen in figure 2. It is clear from this image it is possible to manipulate thick pieces of timber over a frame to produce a sinuous flowing structure. The method of steaming proved most effective and as expected thinner timber strips such as a timber veneer are able to be bent more readily to produce smoother curves. This made it possible to produce a touchstone that embodied these two characteristics both at an individual level and as a collective whole. The veneer strips form a figure eight shape, thus removing any typical start or end point that would normally be present. In addition to this, the strips appear to twist and are responsible for the development of two distinct volumes. This draws back to the key aspects derived from the mobius surface and Klein bottle analysis. Also, it became apparent through experimentation that without some kind of moulding device timber tended to bend incorrectly or even break. From this it can be said that the actual making process is extremely important in determining the extent to which continuity is conveyed.
With this being such a central focus for our project the relationship between structure and continuity needed to be addressed in the final building proposal. This is achieved in a variety of ways. The building cladding follows a similar approach to the Downland Gridshell in that it is placed in such a way to make it appear as though the copper panels are forming long flowing strips along the north-south axis of the building. They also display a degree of curvature and twisting to further reinforce this idea. From an interior perspective one will find timber throughout, but unlike conventional construction these surfaces merge into one each other seamlessly. This is not just limited to the wall, ceiling and floor treatments, but it also includes seating, display cases and ramps. There is also a greater deal of curvature expressed along the wall interior, to create an undulating surface. An example of a building where this sort of approach has already been explored is the Zmianatematu cafe in Poland. In figure 3 and 4 it is possible to see seating arising from the wall and there is a clear integration of the surfaces that make up the ceiling, wall and bench top.
Figure 3. Zmianatematu Cafe, Continuous Structure (Dezeen Magazine, 2012)
In addition to this, the proposed circulation through our building is controlled in such a way to make people experience every aspect. The ramps for instance are not just a walkway, but a functional space for the display of crafts. It is important to note that movement through the building is not intended to be done in a linear manner, but rather by moving in and around the spaces. This is helped by the vertical displacement of each designated space; they are not segregated to a standard floor level. By not following a typical floor layout people will lose a sense of where they started, meaning it is not entirely clear as to where they will end up next, thus, reinforcing the link to the concept of a non-orientable form. As defined by the Downland Gridshell and touchstone there is a strong correlation between continuity and the non-orientable form. By means of bending plywood, veneer and modelling ply strips these ideas have been developed and brought to fruition in our final building proposal. Figure 4. Zmianatematu Cafe, Integrated Seating (Dezeen Magazine, 2012)
STRUCTURAL TREATMENT The double skin forms an important part of the Downland Gridshell construction. This layered approach allows for the grid shell form to take shape. Furthermore, whilst it is not apparent from the outside there is a great deal of structural expression going on within the interior. The timber lattice is completely visible. The façade acts to conceal the building’s function, it is only once someone enters the building that it becomes apparent as to what the space is used for. This is further reinforced by the deliberate high placement of the windows. They are not there for viewing through, but rather as a means for letting light into the building. Before moving on it is important to define what it is meant by the phrase double skin façade. Typically it involves two layers of glazed glass divided by a ventilated cavity (Loncour et al., 2004). In the case study Downland Gridshell the term double skin is actually used to describe the double layered timber lattice forming the shell-like structure (Timber Design Knowledge, 2013). It is therefore necessary to redefine what is meant by double skin in this context. From this it can be said that it refers to the doubling of structural elements. Another building example that shows this is the Savill building in Windsor Great Park by Glenn Howells Architects. In figure 5 it is possible to see how the criss-crossing members come together to form the roof. Our building proposal looks to address the double skin idea in two ways. Firstly, at the main entrance there is a receded glass curtain wall which is framed in timber. This sits approximately two metres into the building, thus, effectively creating a void between the two structures, thus, resulting in the double skin condition. Secondly, the structural framework consists of a series of perpendicular members which come together to form a grid shell. It can be argued that our structure is not a true grid shell seeing as it does not consist of repeating, overlapping structural elements. However, one must point out that the main structural framework is lined with curved timber laths along the interior of the building. In some respects these act as a continuation of the timber frame, therefore, the term grid shell can be deemed suitable.
Figure 5. Savill building roof structure (Glenn Howel ls Architects, 2013)
Figure 6. ETFE skin along the outside of the Beijing Water Cube (Vectorfoiltec,2013)
Our building falls into the category of the flat-vertical envelope as defined in the article by Polo. Being that it is this typology the surface treatments along the north and south facades are particularly important with the surface area for these two sides being the largest. Our proposed faĂ§ade is made up of a series of fins that differ in shape and size. As a large proportion of the building is dedicated to the display of crafts, lighting is kept to a minimum to ensure artwork is easily viewed by the public and more importantly to prevent any damage. ETFE is used instead of glass for numerous reasons. An exemplary example of how this can be applied to a building is the Beijing National Aquatics Centre (refer to figure 6) by CSCEC, PTW Architects, CCDI and ARUP (PTW Architects, 2013). Structurally it is very strong and it has the ability to span relatively large distances. It is a light versatile material which demonstrates good waterproof and air tight qualities (Fabric Architecture, 2013). This is ideal given that our structure is exposed in certain areas due to the openness of the fin design. The fins also provide the building with a means for natural ventilation. Also, from an aesthetic stand point they act to create a sense of intrigue. Passerbyâ€™s are given a glimpse as to what is going on inside without revealing the entire purpose of the building. This effectively acts to bring people inside. As mentioned earlier structural expression is a key underlying principle of the Downland Gridshell especially through the interior. Excluding the entranceway, most of the primary and secondary supporting frame is not visible. However, the glulam and timber treatments are intended to be expressive of the underlying structural framework to create smooth flowing forms. Also, by using glulam it is possible to get a layered effect which is appropriate given that the theme of overlapping has been prevalent right though our project. In figure 7 it is possible to see its use in a building. It is interesting to note, its capabilities as a long spanning material and its application as a bending material.
It is important to point out, that timber is utilised wherever possible in our design in order to convey a more natural quality. Also, given that it is frequently used in modelling it seemed appropriate for a building dedicated to the viewing and production of arts and crafts to be made predominantly out of wood. It brings into question as to why the main faรงade is not timber. The main reason is the aesthetics of it. Upon being exposed to the weather, the timber will age becoming more grey and worn out with time. This outcome is not desirable, hence the need for copper panels. This particular material was chosen as over time it will produce a beautiful green patina, thus making the design even more dynamic. In some regards it is quite fitting to have a non timber faรงade given that the Downland Gridshell building does not either. A considerable amount of thought went into the faรงade design both from a structural and material stand point with the intent of creating a highly expressive interior and a more subtle exterior being the key drivers. It was important to maintain the double skin conditions experienced in our case study and to use timber where possible to encapsulate ideas of crafting and dynamism.
Figure 7. Glulam spanning structure (Western Wood Structure, 2011)
JOINTING Learning from the Downland Gridshell structure (James, et,all) ,a shell is a three dimensional structure that resists applied load through its inherent shape. Therefore, the overall structure is maintained through in plane shear strength and stiffness which provided by preventing rotation at the intersections of the gird members, or by introducing the bracing at each side of the Gridshell. A special jointing system has been introduced in the Gridshell project, the methods of making this joint is showed in figure 1. All of the main structure has been presented by the flat layout pattern at the beginning, with the formation process; the structure can be formed in the right shape. The nodes in each of the domes are very important elements during the formation process as they only need to move vertically towards their final location; hence another monitor was to mark the transverse and longitudinal location of these nodes on the scaffolding platform and checking that those only moved vertically. Another example taken from the Bluestone Project (Barry, 2007), also an example of that shows the benefit of using local material, ex-Oakwood. The beams of the infrastructure are made of ‘glulam’, and they have been constructed of multi-layered, bonded softwoods which are aiming strong standing and more energy efficient compared with metal or conFigure 8. Downland Gridshell, Jointing (James, et, al)
crete. This is again reinforcing for the use of material, which allows very large domed shapes. As our design is aiming for creating continuity interior space, we choose ‘glulam’ which allows large span for achieving our goal for the design. Moreover, it is also a material that allows free shapes of beam, column, etc. The main structure running north-south combined with 6 primaries bracing running east west to give the building strong primary structure to hold those separate floors. Simply joined those with nails and this particular material will divide the interior space nice and smooth. The primary structures running different direction are notched together, the thickness of them are different. Connecting with the ‘glulam’ primary structure, there is Ethylene Tetra Flouro Ethylene (ETFE) which acts as a single layer membrane supported by the primary structure. As the primary structure running different direction allows several intersection, they are also the point that to connect the ETFE. A gutter will therefore starting from the intersection point and collecting water. For those areas that have not got the ‘open façade’, it is also the area where ETFE ends. Above the ETFE,
Figure 9, The Bluestone Project.
the building envelope will connect to the structure by using several pivot joints. As this kind of joint has got the fixed point and also has got one side that can allow turns. This will in turns shape the face more smoothly and continuity.
Arch Daily, The ContemPLAY Pavilion, 2012, <http://www.archdaily.com/258929/the-contemplay-pavilion-drs-farmm/>
Canoeguy’s Blog, Canoe hull, 2012, <http://canoeguybc.files.wordpress.com/2012/07/ribs-04-rk.jpg>
Dezeen Magazine, Zmianatematu Cafe, 2011, <http://www.dezeen.com/2011/08/30/zmianatematu-by-xm3/>
Fabric Architecture, ETFE systems, 2013, <http://fabricarchitecturemag.com/articles/0911_ce_etfe_systems.html
Glenn Howells Architects, The Savill Building, 2013, <http://www.glennhowells.co.uk/content/public/110/0/4>
Loncour, X et al, ‘Ventilated Double Facades: Classification & Illustration of Façade Concepts’, pp. 1-49, 2004, <http://www.bbri.be/activefacades/new/download/Ventilated%20 Doubles%20Facades%20-%20Classification%20&%20illustrations.dvf2%20-%20 final.pdf>
Polo, Z.P, ‘The Politics of the Envelope A Political critique of Materialisim’, C-Lab, Volume 17: 76-105
PTW Architects, Watercube, National Swimming Centre, 2013 <http://www.ptw.com.au/ptw_project/watercube-national-swimming-centre/>
Schleimer, S annd H Segerman, Sculptures in S3, Bridges: Mathematics, Music, Art, Architecture, Culture, pp. 103-110, 2012, <http://bridgesmathart.org/2012/cdrom/proceedings/53/index.html>
State Forest of New South Wales, The Bending of Timber, Series 7: 1-4, 1995, <http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0008/390293/The-Bending-of-Timber.pdf>
Trade Design Knowledge, The Downland Gridshell, 2013, <http://research.ttlchiltern.co.uk/pif294/tdk/case%20studies/structural%20engineering%20of%20 the%20downland%20gridshell/01%20small.htm>
Vectorfoiltec, â€˜The Watercubeâ€™ ETFE surface, 2013, <http://www.vector-foiltec.com/en/products/the-texlon-system.html>
Western Wood Structure, Glulam Structure, 2011, <http://westernwoodstructures.blogspot.com.au/2011_06_01_archive.html>
Wikipedia, Klein Bottle Image, 2006, <http://en.wikipedia.org/wiki/File:Klein_bottle.svg>