Learned Fabrications

Material Agencies For Architecture

ROLANDO MADRIGAL TORRES DESIGN + MAKE 2017 ACKNOWLEDGEMENTS

The author is thankful to Charlie, Edward, Chris and Jez of Hooke Park for provision of invaluable, instruction and time. In addition, deep gratitude should be expressed to Mark Cambell for his continued support during the writing of this thesis.

ABSTRACT

The rise of nonstandard serial design during the mid nineteen-nineties brought about a metamorphose to the economic, technological and visual language that has characterized modes of design and production for the last five centuries (Carpo, Embryologic Houses, 2013). Advancements in computation now allow architectural designers to produce an inexhaustible series of varying digital iterations at a rapid pace. However, it is important to evaluate what the significance of generating a variable series of designs within the context of architectures materialization. Whether designing one or multiple iterations the input of the designer remains crucial as the mediator of the architecture. The language of a digital production does not be governed solely by bits and code but can respond to material realities and in fact, has much to gain from them. There exist great opportunities in the study of the material qualities of the digitally designed. Engaging with the build realities of architecture can represent a means by which the designer learns from the physical qualities of design and can create feedback input for future digital iterations. Interaction with built prototypes can allow the designer to evaluate materiality and uncover new design data from material realities. To explore these ideas this thesis will analyze the development of Wakeford Hall to date and how the build of the Sawmill Shelter helped engage with both digital and material aspects of the project and how a materially informed architecture contributes the evolution of both virtual and material design intentions.

Table of Contents ACKNOWLEDGEMENTS ...... 4 ABSTRACT ...... 4 TABLE OF FIGURES ...... 6 INTRODUCTION ...... 7 CHP 1 – LITERATURE REVIEW ...... 8 Arguing for a Digital Materiality ...... 8 CHAPTER 2 – MATERIALLY INFORMED DIGITAL ARCHITECTURE ...... 10 CHAPTER 3 – PROTOTYPING WAKEFORD HALL ...... 12 Wakeford Hall ...... 12 Technique development: Timber Under Tension Parallel to the Grain Structure ...... 12 Uniaxial Tension Test ...... 13 10-meter Laths ...... 14 Collaboration with Bath University ...... 15 Form Finding ...... 16 Bucket Load Test ...... 17 CHAPTER 4- THE SAWMILL SHELTER ...... 18 1:1 Prototype ...... 20 Material Testing ...... 20 Uniaxial Tension Test V 2.0 ...... 21 Timber Grading ...... 22 Curvature Jig ...... 22 CHAPTER 5-CONCLUSION ...... 24 Bibliography ...... 25

TABLE OF FIGURES

Figure 1 - Uniaxial Tension Test Jig ...... 14 Figure 2- 10-meter lath ...... 14 Figure 3 - Joint A ...... 15 Figure 4 - Joint B ...... 15 Figure 5 - Joint C ...... 15 Figure 6 - Joint designs in collaboration with Richard Sambrook (Sambrook, 2016) ...... 16 Figure 7 - Form Finding Jigs...... 17 Figure 8 - Bucket Load Test ...... 18 Figure 9- Author unknown (1985) The Protoype House working model. Retreived from Hooke Park Servers ...... 19 Figure 10 - HCMA (2014). Grandview Heights Aquatic Centre. Retrieved from http:// www.architecturalrecord.com/articles/11759-making-a-splash?v=preview ...... 20 Figure 11 - Splayed finger jointed scarf ...... 21 Figure 12 - Uniaxial Tension Jig V 2.0 ...... 21 Figure 13 - Test Sample ...... 22 Figure 14 - Knot Area ratio diagrams and failure stresses ...... 22 Figure 15 - Curvature Jig 2.0...... 23 Figure 16 – Spyrydonos, E. (2016) Sawmill Shelter ...... 24

*Uncredited images are by the author and may also appear in the author's Project Documentation submission.

INTRODUCTION

The rise of nonstandard serial design during the mid nineteen-nineties brought about a metamorphose to the economic, technological and visual language that has characterized modes of design and production for the last five centuries. Variability, which has long presented a hurdle for the economies of scale which allowed industrial mass production to thrive had been transformed into a virtue by a new digital age. The capacity to mass-produce series of non-identical items had transfigured a culture of industrial production in which only identical copies were desired and valued into on where differential reproduction is welcome. This new paradigm allows designers to digitally craft script which converses with digitally controlled interfaces and machines that materialize the designed process. (Carpo, The Alphabet and The Algorithm, 2011). The writings of Gregg Lynn (Lynn, 2013) and Bernard Caches (Cache, Philibert De L'Orme Pavilion: Towards an Associative Architecture, 2003) have stressed the role of mathematics, calculus, and continuous functions as new tools of design. Therese was intended to license digital fabrication to produce an array of seemingly inexhaustible design variations at no additional cost. A changing, evolving data flow presented design data as a viable negotiator between algorithmic notational differences and the material. However, if these variations are strictly informationally driven they ran the risk of becoming materially estranged and disengaged from the physical realities of architecture. To date most of the advancement of the digital have been geared towards refining the digital process exclusively and thus being able to develop a series of inconsistent multiples has, in many cases, become about formal variations with little or no unique architectural repercussions. So to what end are these simulations repeated? It is important that digital design must not continue to be strictly geared towards advancements in computing but acknowledge its materialization. If digital iterations can be fabricated and studied, then material realities can begin to form a multimodal interface with digital design intentions. Thus creating alternative iterative design process by which every digital iteration can build on a different variety of inputs which respond to physical realities. For this to occur it is necessary for the material narrative to alter data content so that it may be referenced as iterations are generated and later fabricated; to encode the digital with physical understanding allows the digital to project to produce design data from the richness of the built world. An analysis of materialized digital iterations can create an interface between physical and digital data coalesced to create variation and to inform each iteration.

The object of this thesis is to evaluate how the iterative process of digital architecture can be governed by not just formal possibilities driven by data but also notions of materiality and to propose a role for the designer-maker as an arbitrator between digital and material iterations in an iterative design process. Thru an analysis of the Sawmill Shelter project’s design and build process this thesis will propose the importance of evaluating built realities in juxtaposition with digital constructs to inform future iterations and how the designer by engaging with physical realities of architecture can spark a material responsive design process for digital architecture. In this sense, the primary focus will be how engaging in materiality can help evolve digital iterative process and can thus contribute to the architecture. This thesis will not attempt to challenge the significance of coding in architecture but rather to argue for a further refinement of the digital thru materiality.

CHP 1 – LITERATURE REVIEW

Arguing for a Digital Materiality

Even though the novelty of computing has created a distance of the architects’ involvement in overseeing the fabrication of their buildings in the late 20th century, a vibrant preoccupation with making has never waned within architecture. (Castle, Editorial, 2005) Walter Gropius’ first manifesto for the Staatliches Bauhaus stated: “Artists, architects, sculptors we must all turn to the crafts.” Gropius saw the collaborations of art, craft, and technology as an opportunity these three practices “to become research work for industrial production, speculative experiments in laboratory-workshops where the preparatory work of evolving and perfecting new type-forms will be done.” (Frayling, 2011) Gropius recognized the value in learning from the physical engagement with production as a means of reflection and study. Thus suggesting that materiality can operate as an active agent of evolution and progression informing and contributing to a crafted iterative design process. Being able to analyze the built realities of a digital iteration can be of great benefit. As designers, the exploration of full-scale modeling and prototyping can contribute to reconciling ideas of the digital with the real world. Engagement with the physicality of architecture can be a legitimate mode of design inquiry, where the designer's curiosity affects the architecture and the computer mediates between tangible and digital singularities. This can provide opportunities for truly innovative design research not only in as the architecture materializes but also in virtual space, the spatial representation of information. The use of physical prototypes can allow the digital to be contemplated, evaluated, investigated in its material form. (Burry, Homo Faber, 2005) The integration of different modes of design both physical and digital can facilitate and instrumentalize design. By building digital associative parametric models which are informed by form-finding experiments, with characteristics of materials encoded and project dependencies, these features are retained across all system instances resulting from changes to parametric variables of the digital model. The geometry and interdependencies that characterize the associative digital model can also be informed by material behavior and materialization processes so that the base geometry can evolve in response to the increasing level of articulation of digital and material inputs. Evidencing that negotiating between digital and physical criteria can unearth relationships that can contribute to the designs sophistication. (Hensel & Menges, Material and Digital Synthesis, 2006) Built prototypes can function as a means of design exploration and interrogation. When prototypes are used as a means of reflection for the architecture, it can then be analyzed in an inquisitive manner where the prototype can be evaluated, and the results assist in the design process. The prototypes physical manifestation can be assessed and serve as feedback from which future iterations can be generated, thereby adding complexity to the design process. Where by the design process is intervened by its predecessors, and they are existence echoing in every iteration. Burry explains that “the prototype, once tested and accepted, becomes the archetype for subsequent decisions. The archetype here is taken as the original pattern or model from which all things of the same kind are copied or on which they are based; a model or first form; prototype.” (Burry, Model, Prototypes and Archetypes: Fresh Dilemmas emerging from the the File to Factory Era, 2012) In the materialization of digital models, the physics and the digital have an opportunity to coalesce. Understanding haw digital design intentions translate into the real world can guide decision-making throughout the design process. A detailed knowledge of materials and process combined with a direct engagement with physical testing provides the means by which expertise learned thru the making process can be transferred to computation. Michael Stacey explains that “although we now have access to very sophisticated computational analysis, it is vital for architects, engineers, and designers to remain grounded by physical reality”. (Stacey, 2005) However, Stacey recognizes the use of digital design tools is key to positioning the architect in the center of the construction process, controlling the flow of information and, critically, the generative geometry. (Stacey, 2005) In his introduction to Design through Making of Architectural Design Journal Bob Shiel writes “Most architects do not make buildings – they make information for buildings.” (Sheil, Design Through Making: An Introduction, 2005) While sketches, drawings, models and design data inform the construction of architecture, he considers these to be only a few “among the host of critical and diverse traits required in architectural production”. (Sheil, Design Through Making: An Introduction, 2005) He explains that the making of buildings demands an expertise that is familiar with the tactile and the physical. It is a body of knowledge and experience that goes beyond the production of information. The prospect of realizing immaterial and intangible ideas into built form prompts designers to consider how things are made, and thus, to reflect critically about its potentials. The materialization of architecture can become an immense resource for ideas, experimentation, and research, founded in the physical and the tactile; a tacit experience (Sheil, Design Through Making: An Introduction, 2005)

CHAPTER 2 – MATERIALLY INFORMED DIGITAL ARCHITECTURE

"The most efficient interface design results from combining the forces of sensory richness and machine intelligence." -Nicolas Negroponte, Being Digital- Material behavior can become a vehicle for designs to evolve. For this to happen, it is necessary for the material narrative to alter design data using information derived from physical realities to a digital platform. Studying materiality can be a way to enrich architectural design, offering a different channel of communication from which the designer may cull material meaning for design inputs. Even the most just-noticeable difference can provide insight which a designer can intuitively follow as a design driver; allowing materiality to permeate each construct with a unique appearance, personality, behavior, and purpose. The designer can become an interface by which computers and material can dialog with one another. This exchange is an approach to design where the co-modality between the tactile and the digital can allow the designer to act as an intermediary between the digital and the built. In this sense, the tactility of the designer can be a way to help computers see and hear with the designers as the real time, real life interpreters. Designers can recognize opportunities which arise during the materialization process, dissect them and feed them back as the mediators in a digital material interactivity. The designer retrieves sensory information and transmits it to the digital to be reiterated, unearthing material expression and allowing materiality to be participatory in the digital design process. Digital constructs must not overlook the comparative virtue of the senses. Handling, observing and seeing can allow the designer to evaluate materiality and reacting by perception and intuition creating new prospective material realities which can be tested later and developed into a higher material grammar. Engaging with built iterations of the digital is a means by which designers enhance the digital form thru material study. The procedures detailed during a design process are, more often than not, in need of recalibration, during fabrication as much as they are during conception, in response to the indeterminate nature of material realities which are an inevitable part of the making process. Such rerouting can often initiate an interchange between design intentions and built as the material yields unexpected inputs. There is a high value in an architectural practice founded on the interaction between materiality and design input. While much emphasis has been placed previously put on the dialog between digital mediums of design and fabrication and the immanent materiality, it is important to discuss the role of the designer as the active participant of this composition. In the role of the active spectator, the designer can intervene at any stage of the design process to pursue tangential avenues for the project to evolve. The ensuing materially informed iterations are meant to challenge material understanding and treated with the same degree of skepticism as the original iterations. Every iteration can be treated as an evolved and therefore completely variable subject and probed in search of the indeterminate or the 'art of the accident.'. (Burry, Homo Faber, 2005) To challenge preconceived notions of materiality is to search for expressive patterns in materiality that arise from within the specific allegiances of a given project; a unique material expressions that can transmute architecture. This sort of material engagement can unearth material behavior which can be used as input and thus ensure further digital iterations can present a furthered material language. Equally important is to continue to testing the new digital and physical knowledge gained thru testing and re-iteration. The architecture can be redefined by parameters transmitting and receiving bespoke material information. An organized, interrogative and analytical process can help understand visual order, function, technique that can contribute to negotiating materiality and enhance the project. There is much to gain from a constant interchange between material realities and digital experiments. As the project matures inherent material properties and the digital can evolve into a unified body of knowledge, allowing the architecture to evolve from the cohesive intellectual framework. A digital construct can allow for the cataloging of the build process and assembly, not just the finished product. Each iteration can is documented and the findings used as inputs for its digital reiteration as part of a process to institute material validity and authenticity at the same time. Materiality is an avenue for identifying singularity and uniqueness with tangible expression guiding the designer. The will of material behavior and the process of the process of materialization can be translated into allegiances made by material principles and the digital iterations. The intelligence in a digital project is not located in bits spewed out by the computer but in the collective behavior the architecture. When tacit and digital knowledge is interconnected, material realities can aid the designer in re-coding, storing, dismissing digital design data creating evolved information from iteration to iteration. The designer can choreograph digital coding and recoding as stage directions to establish the desired aesthetic language and feel within the architecture, all deriving from material virtue which facilitates the metamorphosis and the conception and consequent realization of the whole. A deep study of materiality is not intended to oversimplify architecture nor to reduce it to a strict functional rationality. a tacit digital process is always best served by a material representation or consideration translation from one medium to the next. This material feedback loop creates an opportunity for digital architecture to use both the virtual and material realities as part of a multimodal iterative design approach. CHAPTER 3 – PROTOTYPING WAKEFORD HALL

Wakeford Hall The design for Wakeford Hall began with an analysis of the open competition for Wakeford Hall competition. The competition was an invitation to all AA members to participate in the design of the Wakeford Hall at Hooke Park, the Architectural Association’s woodland campus. Since the build is supposed to span over several years and to be developed by separate groups of students of the Design and Make graduate program, the competition was an ideas completion which called for the entries to be more guided to prompts rather than to finite architectural schematics. The nature of the project allowed us to use the first months of this project to dissect and evaluate the competition entries with the winning competition entries along with the honorable mentions providing the main design prompts. An effort was also made to assess the rest of the entries to gain a developed understanding of what, as a whole, the Architectural Association’s community’s vision is for Wakeford Hall. The common theme in the proposals was for Wakeford Hall to embody the essence of the Forrest and for it to acknowledge the unique context of where it is situated. Incorporating the aspects of the Forrest along with the key architectural elements provided by the two competition winners and two honorable mentions would give us the groundwork for beginning the development of our project. The main design drivers extracted from the competition were that of the use of tree-like columns, an articulation to the surrounding landscape, a core space around which the programmatic volumes could be arranged and lastly a sweeping forest-like canopy roof structure. The latter is of particular importance in this thesis as it will be the focus of the ensuing research. The other aspect to consider for the development of Wakeford Hall was the need to consider effects of a build which is meant to span over 3-4 years and to be developed by several different groups of Design and Make students. Thus, prompting questions over what is the best way to engage with the project and how this altered the dialog with our incoming colleagues. The most important consideration was to facilitate the hand-over of the project. Hence the group decided to begin the build with a superstructure that would later house the programmatic volumes that would contain the functional spaces of Wakeford Hall. The development for this year was then focused on developing a palate of techniques and research that could be continued by the waves of incoming students and or propagate future design agendas. The initial design phase would kick off an open design process for Wakeford Hall that will allow the incoming years to have the freedom to develop their architectural propositions in unison or contrast with this year's research, whichever is most fitting. For this reason, the Wakeford Hall project began a period of individual technique development where material exploration would generate avenues for project’s evolution.

Technique development: Timber Under Tension Parallel to the Grain Structure My technique development began as an exploration into the natural mechanical behavior of timber, specifically, timber under tension parallel to the grain structure. According to the University of Cambridge, timber wood has extreme anisotropy because 90 to 95% of all the cells are elongated and vertical (i.e. aligned parallel to the tree trunk). The remaining 5 to 10% of cells are arranged in radial directions, with no cells at all aligned tangentially. The molecular structure of timber allows it to have a rope-like mechanical behavior when a tension load is applied across the length of the timber. The load capacity of timber is 30-50 times greater parallel to its grain in fact (Pemberton & Greer). Timber is the oldest known building material. However, this inherent mechanical behavior remains largely unused, and its research grossly underdeveloped. The typical applications of timber have led to the development of research into timbers behavior while under compression, bending and shear forces. Although the strength of timber as a tensile member is comparable to that of it as a compression element the research into timber under tension along its grain structure has not been explored significantly. The lack of the investigation presented a real opportunity to investigate and probe timber in an innovative manner to build up our knowledge in an intuitive, tacitly informed manner. The initial studies were intended to demonstrate the potential in the timber as a tensile component. The findings served as a catalyst extrapolated into architectural elements and help to speculate over their spatial implications. The following examples are part of an open- ended exploration of tensile strength in timber.

Uniaxial Tension Test

With the current lack of research into the strength of timber in tension parallel to its grain structure, it was crucial to confirm just how strong timber actually could be as a tensile element. Without access to a testing laboratory at Hooke Park as a first step, there was a need to develop a series of a testing jigs in-house that could allow us to test timber to failure. By reverse engineering a hydraulic ram (700 bars working pressure) a test jig was designed that would enable conducting a uniaxial tension test to failure test to begin the assessment of timbers tensile strength. (Figure 1) The first samples tested were 50 x 50 x 300mm. However, it quickly became evident that they needed to be sized down as the samples were causing to shear the 12mm bolts they were anchored with. The solution was to create a bow-tie shaped sample that would taper smoothly to a section of 5 x 5mm to “manufacture” a weakness in the timber so that the timbers could be tested to failure. Of the 30 samples tested, 15 were fabricated from Norway Spruce and the remaining 15 from European beech. The samples yielded a load bearing capacity of

Figure 1 - Uniaxial Tension Test Jig between 40 kg to 45 kg per square millimeters without a noticeable difference between the two species. Acknowledging that the test samples were manually fabricated and the test jig was designed using materials and kit which were not intended for this use the results can only be interpreted as an insinuation of the timbers properties, however, the results were indicative of the proposed strength of timber under tension (Pemberton & Greer). The results encouraged the speculation over timbers potential application as a tensile structural element.

10-meter Laths

With the reassuring findings from the uniaxial tension test, the next phase became about how to compose long timber laths that could act as long tension members in a potential roof system. This exercise was the first attempt at designing a joinery technique that would allow us to fabricate long members from varying lengths of timber. Parallel to the developing an understanding of the fabrication and assembly process was the need to evaluate an understanding of how a scarfed length of timber would behave while under tension forces and its resulting geometry. All of the test samples were made using Western Red Cedar timber with a section of 30x100mm. These tests also helped to compare the effectiveness of using mechanical fixings versus that of bonding adhesives.

Joint A: Half scarf joint (Figure 3) Components: 3 x 3.5 meters long lengths, 16 M6 x 40mm screws Conclusions: demonstrated failed very quickly. There proved to be a weakness while taking up curvature as the joint’s geometry has an abrupt change in direction at 90 degrees which introduces a moment while in bending. This made evident the need for the geometry to be spliced with any changes in geometry should be tapered so that the forces applied could have a continuous surface to flow through. This sample only used mechanical fixings. Prefabrication of the length was 30 minutes and assembly time was 40 minutes.

Joint B: Splayed scarf joint (Figure 4) Components: 3 x 3.5 meters long lengths, 12 M6 x 40mm screws, 2 part epoxy resin adhesive Conclusions: performed very well. As the seen in, image X, we were able to load the 10-meter length with the weight of 10 people (roughly 700 kg). It worth noticing that the geometry of the lath was made up of only one planar cut, which reduced the time of production to about 15

Figure 4 - Joint B minutes and the time of assembly to 45 minutes

Joint C: Stop-splayed undersquiented scarf joint (Figure 5) Components: 5 x 2.3 meters long lengths, 2 part epoxy resin Conclusions: performed well although there was a failure away from the joint along the timber as there was large knot which went undetected during the assembly of the lath . This made evident the need to grade out inconsistencies in the timber should be of significant consideration considering the size of the samples. Also, the saw-tooth geometry of the scarf caused a significant increase prefabrication of the components as well as demanding significantly more time to fabricate and about 2 hours and 45 minutes to assemble.

While the observations made for these studies were rough estimates and lacking in precision, they served a great benefit when informing the direction of design for later iterations. Due to the relatively small size of the cross section, to hang the 10-meter lengths it was necessary to oversize the ends of the connections to ensure that the samples did not fail at the anchor points as this would prevent from further examining the behavior of the joinery. At present, the end connection was not being considered in the studies but being able to load the samples, most notably Joint B, did immediate concerns about the design of the end connections and their potential frailty as it started to become apparent that we would be able to submit these timbers under great stress. The remarkable performance of Joint B and Joint C helped us to further consider the use an epoxy resin as it seemed to be resistant enough on its own. As observed in the uniaxial tension test the tensile strength of the timber was very high and we could potentially use much smaller timbers than the ones tested in these studies to create our laths. This is important as there would be a great advantage in being able to eliminate mechanical fixings from the joinery altogether as any fixings introduced into the timber would remove a significant amount of volume from the smaller timbers, thereby compromising the tensile strength of the timber.

Collaboration with Bath University Soon after these studies, a collaboration began with engineer Richard Sambrook, an MSc candidate at Bath University. The object of this partnership was to aid in the development of the proposed timber tension roof for Wakeford Hall, specifically the joinery techniques for the timber laths. Having evaluated the early joinery studies at Hooke Park (Joint A-C) and using them as prototypes, the collaboration provided the opportunity to study alternative joinery solutions in a more scientific manner at the laboratories at Bath University. Richard Sambrook’s thesis dissertation titled “STRUCTURAL BEHAVIOR OF INNOVATIVE TIMBER SCARF JOINTS IN TENSION PARALLEL TO THE GRAIN” used an “experimental and analytical study will investigate the structural behavior of traditional carpentry scarf joints under pure tension.” (Sambrook, 2015) A total

Figure 6 - Joint designs in collaboration with Richard of 24 samples, 140 x 40 x 480mm in cross-section were tested with the aim of the research was to be able to evaluate different joint configurations as well as developing theoretical models that could predict the structural response and failure modes of said joinery. The designed scarf joints utilized dowels tenons, notching, pins to provide the splayed scarf joint with tensile resistance; the asterisks denotes the scarf joints selected for manufacturing at Hooke Park and testing at Bath University. (Figure 6) The designs for testing were chosen primarily on the basis of ease of fabrication in order to ensure a high standard of quality control in anticipation of the joinery that could be used during for the upcoming summer build. The experimental results demonstrated failures in shear parallel to the grain mostly due to an interruption of the samples grain created in the scarf geometry to accommodate the both the square-key connection and the multiple key connections while the screwed scarf joint demonstrated a much higher load capacity. (Sambrook, 2015)

While additional research and design considerations were necessary to increase the understanding of the structural behavior the splayed scarf joints under tension the work done in collaboration with Richard Sambrook and Bath University helped to examine as well as discard some of the potential strategies being considered for the sliced scarf geometry to be used in Wakeford Hall. The keyed connections tested demonstrated the geometry needed to fit the keys produced an interruption of the grain of the timber causing it to become susceptible to failure under tension parallel to its grain. Moreover, while the screwed splayed scarf joint outperformed the keyed connections, it becomes apparent during the initial design iterations that metallic fasteners would prove inconvenient on smaller section timber.

Form Finding Parallel to the design of the joinery, it was necessary also to consider the architectural implications of what a timber tension roof could become. The original proposal for the timber tension roof was for it to be a sinclastic catenary structure. However, prompted by a conversation with Arup Group engineers over the possibility of the timber tension roof structure being an anticlastic doubly curved surface a series of physical form finding exercises were developed to study the possibility of generating a timber tension net that could serve as the roof structure. What followed was the development a jig that could help transform a timber tension net shape by adjusting it at the anchor points. Due to the anticipated light weight of the structure, the principle was that a doubly curved net structure composed of two layers pulling in opposing directions could help to add rigidity to the net structure without the need to weight it down as would be necessary with a catenary structure. (Figure 7)

Figure 7 - Form Finding Jigs

The purpose of these studies was to begin to assess the geometry that could be generated by a timber tension net. The timbers used for the Jigs were at a scale of 1:5 from the original Joint test A-C, and as a consequence, the issues of grain interruption and knot size encountered earlier were much more prominent. Although this was only meant to be a formal exploration, it suggested that should we continue to reduce the section of the timbers for the roof structure the impact of even small knots would be considerable in smaller sections and would increase the likely hood of failure from grain interruption. Furthermore, the jigs raised issues over the anchor points and the importance that these would have for a full-scale structure. Due to the proportions of the timbers (roughly 1 to 3 in height to width), it became apparent that a timber with a rectangular section would have much more trouble taking up the double curvature required as well as being unable to coincide with the other crossing timbers at the junction points. This prompted the move to using a square section timber which could be more suitable for an anticlastic net structure. Additionally, the exercises helped to gain insight into the potential assembly and construction strategies, details of the end connections as well as geometrical arrangements for a full-scale structure.

Bucket Load Test Having begun a series of digital iterations in addition to some of the early prototyping made evident that a square section would be advantageous for a double curved roof lath needed to fit the geometry coming from the digital models. To optimize the section of the timbers, a test wast set up to load a timber lath of 5 meters with 14-liter buckets spaced 350mm apart across its length. Initially, there were samples selected for testing ranging from 70 x 70mm down to 26 x x26mm in cross-section. The ideal size for the section of the lath would be chosen on the basis that it would need to be big enough to allow a joinery solution and takeup the tension forces yet small enough to take up curvature without having to be submitted to a great bending stress. By filling the buckets with water, we were able to simulate vertical point loads along the lath that could act as the points possible intersections of the roof geometry top layer. Additionally, the lath was ratchet strapped to the rig to simulate a horizontal load that would generate double curvature (Figure 8). Over the span of 5 meters, the lath was able to take up over 370mm of curvature both in elevation and plan views which were satisfactory as it approximated the anticipated curvature needed coming from the early digital models. The section selected was 38 x 38mm. It was noticeable, however, that for a section this size and in this application sapp wood and knots needed to be limited to the extent possible as the failures from in the laths all occurred at either large knots and or portions of the lath where there was a lot of sapp wood.

Figure 8 - Bucket Load Test

These tests were all done in-house to build up our tacit understanding of the physical realities of timber under tension and in response to the early digital models. The innovative character of the structural proposal necessitated the confirmation of the feasibility of the structural in material terms. While it must be acknowledged that these tests are the test modes were in a sense scientifically unsophisticated, the modes of testing are all bespoke and derived from direct project specific necessities. It was necessary to examine suttle nuances and opportunities in timber under tension and how these could be translated to a timber net structure. From the outset this project was driven by an innate tensile behavior in timber, building on principle knowledge thru material testing.

CHAPTER 4- THE SAWMILL SHELTER Having understood the natural strength in timber under tension and its potential applicability as a tensile structural component the next step is the acknowledge the obvious need to add to the body of knowledge of timber under tension. This allows the rethinking of how to utilize timber as a tensile element, its applicability and more importantly the spatial qualities generated by a tension structure. The Grandview Heights Aquatic Centre (2014) in Surrey, Canada by Hughes Condon Marler Architects (Figure 10) and the Prototype House (1985) at Hooke Park, Dorset, UK by ABK Architects and Frei Otto in partnership with BuroHappold Engineering (Figure 9) are two rare examples of timber under tension being utilized as the primary structure for a roof. Both are catenary structures with one utilizing glulam timber beams and the other round timber poles, respectively, as the tensile members with the timbers supported at the ends while hanging under their weight and that of the roof cladding. There are nearly 30 years in between both of these projects, yet the structural concept utilized in both buildings are the same in principle which begs the question, why in 30 years timber under tension has not been taken further? The difficulty in the applicability of a timber tension is possibly the principle reason for why it is underdeveloped, however, Hooke Park and the Design and Make program are the perfect places to conduct this study and tap into its immense potential as an architectural component. Thus, the research continued as an exploration into maximizing this natural strength in timber and how it could become a conceptual driver for the roof structure.

Figure 9- The Protoype House, ABK Architects and Frei Otto

Figure 10 - Grandview Heights Aquatic Centre, HCMA 1:1 Prototype The translation of the Forrest atmosphere and the key design drivers of the Wakeford Hall competition were re-designed and translated into an architectural proposition. The extrapolated design drivers were a fluid timber net system would be held up by tree-like columns under which would lie the programmatic volumes which are separated by interstitial spaces which allowed the rest of the campus as well as the woodland to permeate the project both the landscape and the user. The early development and studies for timber as a tensile structural element prompted the concept of using a tensile timber net as the flowing roof structure for Wakeford Hall. However, there was still much unknown about the feasibility of this structure in timber as this roof would be the first of its kind. The Sawmill Shelter presented an opportunity to develop a full-scale model of a timber net structure that could serve as a 1:1 prototype for the Wakeford Hall roof to be built the following years. Functioning as a 1:1 prototype the Sawmill Shelter roof was meant as an exploration that would output configurations of a fluid timber tension roof system and serve as an example of the nets spatial qualities and their applicability for Wakeford Hall. As the Sawmill Shelter project only needed to observe some basic functional programmatic requirements (operating volume of the portable sawmill and spatial requirements for the operator), the focus for its development remained on further developing the techniques with a potential applicability for the Wakeford Hall roof system. These included mainly the roof components such as a timber tension roof, a cladding strategy, the anchor and foundation system as well as the development of digital form-finding models. Additionally, the Sawmill Shelter presented an opportunity to explore an alternative tensile flowing structure that could permit a different reading of a tensile roof stepping forward from the more traditional Frei Ottoesque pitched tent language. The original structural ambition for the Sawmill Shelter was to build a simplified version of the roof geometry envisaged for Wakeford Hall. As the timber tension net was, in essence, an experimental structure, it was key to reduce it to its core elements to provide a test bed that would allow us to test and study the basic principles of a timber tension net. Building on the knowledge from the original prototyping work it was necessary to undergo a subsequent testing stage that could respond to the digital models and the structural analysis being done by Arup Group engineers as a way of assuring the feasibility of such a structure. Many of the deciding factors in the geometry of the structure were driven by conservative assumptions that were being made about the performance of the structure. While the digital models were able to provide feedback in regards to the stresses that the tensile members would be under it was still unclear if we could test consistently to resist these loads plus a reasonable margin of safety. The importance of having Arup engineer the performance of the building was that no longer were we relying on pure tacit knowledge, but digital information was beginning to inform the projects materiality. Thru digital structural analysis, we could understand better the forces that the structure generates and could now revisit the physical and more tangible aspects of the structure.

Material Testing Given that the early uniaxial tension test demonstrated that the tensile strength of the timber would suffice to take up the stresses anticipated for this type of structure, it was then necessary to finalize the design for the timber to timber joinery. This would allow a means fabricate the lengths of timber required to span the 10-meter length of the structure. Some initial alternative solutions, such as finger jointing were explored, but it quickly became apparent that it would be difficult to replicate the precision and quality of industry manufactured joinery at Hooke Park without access to the proper production equipment. However, we were able to extrapolate the finger jointing technique and combine it with the early proposals to create a finger-jointed splayed scarf. By using a handheld router with a finger jointing router bit, we were able to create a finger joint along the length of the splayed scarf (Figure 11) which in conjunction with the right adhesive could potentially provide us a joint strong enough to take up the anticipated loads from the structural analysis.

Uniaxial Tension Test V 2.0 To test this joinery technique a more sophisticated version of the first uniaxial test was designed that could test larger samples (Figure 12). The initial testing for yielded favorable results such that failure in the sample was not presented in the joinery but that the end connections after at an average of 1.2 tons. This was important as this test mode also gave us a means with which we could optimize the end connection’s specifications. Once the end connection was improved so that it could undergo the tests we were able to test 40 samples using two different types of adhesives, one being an off the shelf wood polyurethane adhesive and the other a two-part epoxy resin. The two performed fairly similar breaking consistently between 30-40 kN (Figure 13). However, the two-part epoxy resin was better suited for our particular application as it could accommodate the moisture content of the green timbers being, was specified with more elasticity and has gap filling properties.

Figure 12 - Uniaxial Tension Jig V

Figure 13 - Test Sample Timber Grading The quality of any timber stock can vary greatly, but particularly in the case of Hooke Park as the woodland. Hook Parks woodland had previously been undermanaged for many years adding to the unpredictability in the quality of the timber. Taking into consideration the size of final cross sections of the timbers (38 x 38mm) it was crucial to grade out any defective timber as even the small knot will weaken a section of this size. The timber stock which was available to us for this build was composed of logs averaging 5 meters in length and of varying diameters. Having milled and planed the timber down to lengths of 38 x 38 x 5000, it became apparent that grading out all defective timber was not plausible as this was mean that over two thirds for the timber would be wastage. By using used standard timber grading criteria, knot area ratio diagrams and a 3 point test to failure we were able to develop our own timber grading parameters that would ensure the timbers being used would be comparable to that of a straight grained, knot free timber under tension. 5 of the 6 samples with a knot percentage of 12% or less performed just as well as a straight grained knot free piece of timber Figure 14 - Knot Area ratio diagrams and failure stresses which failed consistently at 200 kg, and thus this was a knot area percentage ratio which we felt comfortable would not compromise the structure. (Figure 14)

Curvature Jig Once the timber was graded, and the laths were joined to make up the lengths needed it was necessary to undergo a final test to have a degree of quality assurance for the joinery and grading across in the laths which, especially the ones that would be under the highest stress. The approach was to design a large improved version of the early bucket loading test so that we would be able to apply point loads to the laths at the intervals where the junctions were meant to happen in the structure as well as bend the full length into its approximate of the geometry. (Figure 15)

Figure 15 - Curvature Jig 2.0

In the big picture of Wakeford Hall, the Sawmill Shelter served as a full scale test bed which helped answer many of the of the original question regarding the timber tension system’s such as the feasibility of using timber as a tensile structural element, a global roof geometry (sinclastic or anticlastic), the tensile element’s section size, types of connections (timber to timber, end connections, ground connections, etc), which species of timber would best suit this application. Additionally, once finalized it helped prompt new fundamental issues over the inhabitation of the spaces created by the canopy. The Sawmill Shelter gave us the opportunity resolve, to some degree, some of the technical aspects of the timber net structure which were unknown at the beginning. Additionally, the project helped to understand some of the fundamental principles of a timber tension roof’s mechanical behavior as well as evaluate the spatial geometry, function and esthetic significance of a swooping timber tension roof. This build was essential to understanding the relationship between the different elements of a timber tension net system and how they perform in unison. However, the largest contribution of this for Wakeford Hall and the potentially redesigned iterations which can be built on a more complex palette of inputs and response to the success and limits for the Sawmill Shelter. The real significance of the Sawmill Shelter is how its successes and limits can further the language of the tensile timber net and expand the governing ideas and principles of what the roof for Wakeford Hall can be. Having insight into the roof’s geometry and curvature, the prefabrication process, the testing and the build process among others can be translated into material information to be integrated into future digital design iterations.

Figure 16 - Sawmill Shelter

CHAPTER 5-CONCLUSION

The design of the timber tension diagrid net that composes the roof structure for the Sawmill Shelter was the after effect of an inquisition into a mechanical behavior in timber, tension parallel to the grain structure. Its potential applicability in combination with a digital iterative design process can serve as a provocation for the continued development of the Wakeford Hall. As a result of a design proposal that was driven by material research and informed by digital iterations, It is worth acknowledging that in this particular case the focus was primarily on the structure of the project and not so much the architecture. This is in large part because of the unknown variables which needed to be resolved in respects to the structural proposals behavior, assembly and the building components. However, this experimental structure value lies in the opportunity to evaluate it and further its principle findings. It is important to note that while there wasn’t a complex level of associativity between the digital design and the material realities of the Sawmill Shelter each digital iteration was not reinvented but was built on the knowledge attained from previous generations along with cross-referencing, to a degree, the material testing. As a result of the interrogation between the physical and the digital, each iteration was progressively evolving. This assured that each digital iteration for the Sawmill Shelter transcended its predecessor as a consequence of the interaction between physical limitations and opportunities. The Sawmill Shelter is an experiment which should allow us to learn from a new typology of structure thru every iteration across an extended period. The completion of the build does not mark the end of the design explorations. It is important that the results of the build be analysed and reinterpreted. The experimental approach which formulated the design of the Sawmill Shelter must now challenge the findings that came about as a result of the build and to the degree possible the architecture repercussions this system must now come to the forefront of the continued development to be undergone in the coming years for Wakeford Hall. The results, such as global geometry, patterning, assembly strategies, spatial performance among others must be analyzed and fed back to the digital models. This build should be understood in the larger context of Wakeford Hall. As a means to transfer knowledge mapping the possibilities of growth for the project, methods of production and lessons from fabrication can all contribute to the body of knowledge and how the incoming groups can learn from this building. The following stages of Wakeford Hall should use the Sawmill Shelter as a pallet of material strategies for a tension timber net. The findings from the build of the Sawmill Shelter can become information overlayed on top of the next design propositions for Wakeford Hall.

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