Combining Advanced Computation Methods with Tradition

Combining Advanced Computation Methods with Tradition A Reciprocal Frame Prototype using Invasive Wood Material Junhong fu (MLA + UDC) Lizzie Needham (MLA) Evelyn Saunders (BSArch)

Research Studio|Fall 2020 Studio Report no.: 03 Wood Proto-Architecture 3.0

Integrating design computation and materialization Studio Instructor: Assistant Professor

Ehsan Baharlou, Dr. -Ing

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Contents

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Chapter 01: Introduction

Page 05

Chapter 02: Context and Relevance

Page 11

Chapter 03: Exploring Material Properties Page 15 Chapter 04: Design Outline

Page 21

Chapter 05: Joinery System

Page 25

Chapter 06: Form Finding and Structural

Design Page 35 Chapter 07: Fabrication

Page 43

Chapter 08: Outlook

Page 53

References

Page 59

Acknowledgements Page 63

Chapter 01 Introduction

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RF Structure by Authors (Source: Daly, Tom)

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(1.1)

(1.2)

(1.3) (1.4) (1.5) (1.6) 6

7 (1.7) (1.8)

(1.9)

(1.10)

FIGURE 1-1: Flying Cloud reciprocal roof frame (Source: TimberHomes)

Reciprocal Frame Structures This research investigates how advanced computation and fabrication methods can push forward the traditional building technique, Reciprocal Frame construction. The Reciprocal Frame (RF) structure is a self-reliant unit composed of mutually-supporting beams that can be aggregated in a three dimensional grid. Our project focuses on RF structures that are composed by a series of modular triangulated units that rely on each other spanning between two anchor points to form a freestanding RF arch prototype. RF structures provide designers with opportunities to create original and engaging curved forms using straight building materials, which can be iteratively explored and pushed with the aid of parametric design tools. Furthermore, RF structures can be easily constructed with a simple joinery system and

FIGURE 1-2: Geometrical parameters of a reciprocal unit (Source: Sketch by authors)

still maintain high levels of structural integrity as a tensile form. Advanced computation methods and digital fabrication offer new opportunities for novel RF form development through precise structural analysis, material intelligence, and assembly planning.

State of the Science In the book, Reciprocal Frame Architecture, Olga Popovic Larsen discusses the methodologies behind constructing a Reciprocal Frame. She claims, in order to design and construct a Reciprocal Frame (RF), a detailed understanding of the geometry and its parameters is important. Based on her research pointing to regular polygon reciprocal unit made with beams, our study deals with cylinder-like pieces, the parameters are as follows:

- Number of pieces in each unit ( ) - Radius through the outer supports (

- In a section view, plan lengths between intersections ( , )

)

- Angles between pieces and supporting plane ( )

- Radius through unit pieces connecting points(PCPs) ( )

- Radius of structure pieces ( ) - Vertical rise from the outer supports to the PCPs ( ) - Vertical spacing of the center lines at PCPs ( ) and lower center line to the support plane ( ) - Length of the pieces ( ) - Length of the segments divide by PCPs (

,

)

- Sector angles between pieces in plan view ( ) - Overall length of the piece in plan view ( )

The relationship between vertical rise ( ), the piece thicknesses ( ) and the connecting locations ( / ) can be determined from the equations above (1.11.10), and this will be discussed later in Chapter 04.

(Popovic Larsen, Olga)

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FIGURE 1-4: Invasive species in Charlottesville, VA (Source: Authors)

Use of Invasive Species as a RF Building Component

FIGURE 1-3: Paulownia tomentosa grows in an abandoned building in Charlottesville, VA (Source: Authors)

Another important aspect of this research is the use of an invasive tree species, Paulownia tomentosa, as the primary building material. Invasive plant material makes up a significant portion of human environments, but is often overlooked as a construction material. Reciprocal frame structures allow for the use of young invasive wood species as irregular materials do not hinder the form or structural integrity. According to the National Wildlife Federation, “species that grow and reproduce quickly, and spread aggressively, with potential to cause harm, are given the label “invasive.”” (National wildlife federation) These characteristics lead to potential construction materials that are prolific, low-cost, and renewable, thus making them a good fit for the rapid assembly typical of reciprocal frame

structures.

From a management perspective, invasive tree species should be harvested as saplings to prevent further spread and reproduction. Juvenile invasive tree species cannot typically be processed into solid wood products due to small caliper dimensions and inconsistencies within the material characteristics.

Reciprocal form offers a solution, allowing one to build complex forms using young and unprocessed lumber products while simultaneously helping to manage local ecosystems. This research explores the potential of using an invasive tree species as the foundational material for a reciprocal frame prototype installation, which we believe can create an engaging, anthropomorphic installation that speaks to broader cultural and ecological contexts.

Chapter 02 Context and Relevance

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Complex Timber Structure 2 (Source: Gramazio & Kholer and ETH Zurich)

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Context and Relevance Computer Aided Design Our research responds to an interest in modernizing traditional RF construction methods through advanced computation design. In particular, our work finds inspiration in a growing body of work that uses new technologies for generative design and precise fabrication.

Form Finding

FIGURE 2-1:Lamella Flock (Source: CITA, Knippers Helbig Engineers and Trebyggeriet.no, )

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Lamella Flock, a research project developed by students at the Royal Danish Academy of Fine Arts, School of Architecture, uses complex fabrication processes to create unique, freeform RF structures (fig.21). Lamella Flock’s form is found through a bottom-up generative design tactic based on the relationship between the interdependent linear units. The system allows for designers to form find within the achievable parameters of the lamella network. Their digital chain includes an Finite Element (FE) analysis and checks for structural behavior, so they can assess feasibility of construction as they move through design iterations. Our research seeks to build upon this exploration, and also determine if it is possible to generate form through topdown design iterations.

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Precision of Fabrication

FIGURE 2-2:Complex Timber Structure 2 (Source: Gramazio & Kholer and ETH Zurich)

While RF structures are relatively easy to construct, they rely on precise placement of the units in order to function. Robotic fabrication methods provide solutions for advancing precision. Complex Timber Structure 2 (fig. 2-2), created by Gramazio & Kholer and ETH Zurich, utilizes the computer model to robotic fabrication process for exact cut placement and angle of connections within RF units. This project transmutes reciprocal knots along a curved funnel using intelligent generative systems and an innovative fabrication process which developed the complex form. Generative digital tools and 5-axis milling are highly important here, as is calibrated spans and offsets, or ‘misalignments,’ that offer tolerances within the demanding geometry.

Material Sensitivity As designers, we feel excited about the possibilities that RF structures offer for material intelligence. With a precise assembly plan, RF structures can be composed out of most all linear material. This opens up opportunities for using materials often overlooked in architecture and fabrication. In our research and in our own work we value material use that respects wood’s origins and site vernacular and also conveys important social-ecological narratives.

RF as a Response to Site

FIGURE 2-3:Mount Rokko- Shidare Observatory (Source: Hiroshi Sambuichi and Ove Arup)

Mount Rokko-Shidare Observatory (fig. 2-3), designed by architect Hiroshi Sambuichi and Ove Arup and Partners in Japan, demonstrates the combination of RF structures with material sensitivity and careful site analysis. The observatory’s dome-like open form speaks to the Rokko Mountain landscape and facilitates natural ventilation. The air movement facilitated by this form couples as a sound installation as the voids within the materials sing while the wind passes through.

The RF pattern shifts in density according to sunlight to also serve as a shade structure. Our project strives to incorporate the ethos of the site with a desire to foster human engagement and comfort as demonstrated in the Mount Rokko- Shidare Observatory.

FIGURE 2-4:Ryuboko Hut reciprocal units (Source: Ashizawa Ryuichi laboratory + Toki Hirokazu)

RF as a Response to Material Unlike standard construction methods, RF structures open new possibilities for innovative form finding with unprocessed wood products. Rather than process lumber into a product where its original living state is unrecognizable, RF structures are able to display wood’s unique characteristics. Ashizawa Ryuichi laboratory and Toki Hirokazu’s Ryuboku Hut use recycled driftwood as the components for a RF structure (fig. 2-4 and 2-5). Although driftwood is not considered to be traditional building material, the structural integrity due to mutually-reliant beams in RF construction allow for their use. The designer’s material choice speaks to the cultural history of the landscape, and becomes an installation that serves as a resting place for local fisherman.

FIGURE 2-5:Ryuboko Hut (Source: Ashizawa Ryuichi laboratory + Toki Hirokazu)

Chapter 03 Exploring Material Properties

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Harvesting Princess Tree Saplings (Source: Authors)

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Hollow chambers in Pith FIGURE 3-1:Cataloging invasive species in Charlottesville, VA (Source: Authors)

Exploring Material Properties The adaptable nature of RF structures we found in our research prompted further exploration of the use of unprocessed wood as a scalable building material. This also supported the use of an invasive tree species in the interest of ecological problem solving and acknowledging the reality of materials readily available in our local environment. So we went about harvesting wood in the surrounding area.

Determining the Right Species We began our material research through harvesting, cataloging and analyzing ten problematic invasive tree species in Charlottesville, Virginia. Our material choice was determined by local availability, ease of harvest, and material characteristics. Out of the ten tree species, our research tested these factors

FIGURE 3-2:Understanding Princess Tree (Source: Authors)

through analog exploration of seven of these tree species: Albizia julibrissin, Paulownia tomentosa, Broussonetia papyrifera, Morus alba, Acer platanoides, Ulmus pumila and Ailanthus altissima. From these we selected Paulownia tomentosa as our material for prototype fabrication (fig. 3-1).

Choosing Princess Tree, Paulownia tomentosa Paulownia tomentosa is considered to be an invasive species in Virginia, as it quickly colonizes disturbed landscapes, often out competing indigenous pioneer species. Paulownia tomentosa, or, by the common name, princess tree, thrives in environments most plants consider to be “harsh” including roadsides, railroads, parking lots and floodplains. It is a fast growing tree that has been recorded to grow as much as 7’ per year as a juvenile. Through our own material exploration, supported by further research, we discovered this is due in large part to the hollow pith chambers called stem voids with which the trees grow until they are approximately three years old.

The species is classified as a hardwood, is porous, lightweight and easy to work. Research and material

experimentation led us to believe that Paulownia tomentosa was the best fit for our RF research for the following reasons: (1) Dryness. Lumber will dry completely in 30 days, without kiln drying.

(2) Workability. As it is light weight with a predictable straight grain.

(3) Strength. Wood is not prone to splitting and cracking, and is quite strong.

(4) Character. Hollow pith chambers offer an interesting design opportunity, through their use in a joinery system.

(5) Vigorous Growth. Paulownia tomentosa is readily available in Charlottesville, VA, and our explorations made it clear that landowners were more than happy to allow us to remove the trees.

Sapling material light and minimal caliper

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Best results with unprocessed wood

Maintenance strategies leads to straight trunks

Stem void utilized for joinery system

FIGURE 3-3: Responding to material characteristics and the reciprocal unit (Source: Authors)

Chapter 04 Design Outline

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RF Structure Study Model (Source: Authors)

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Design Outline

Computational Foundations Precise connection is critical to form a reciprocal frame. The three connection types between reciprocating pieces are: edge-to-edge, edge-to-end, and end-to-end (fig.4-1). If the material is leaning to be processed with modifications on its end or side, the center line spacing (h2, detailed later in this text) is likely to decrease, allowing a horizontal or even planar structure to be created.

Edge to Edge (-/-)

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According to the book Reciprocal Frame Architecture by O. P. Larsen, previous computational research has investigated dimensional variation within reciprocal frame structures. This includes the effects of variation in spacing between the centerlines of reciprocal pieces at their connection points (Chilton, Choo and Popovic, 1995; Popovic, 1996). The chart here (fig.4-2) shows this relationship within a reciprocal unit, where the ratio of the inner radius (ri) and the outer radius (ro) decreases, the two circles become more similar. This result is in the defined spacing of piece connection points (PCPs) account for the increase of the entire rise (ratio h2/H decreasing), which therefore means that the whole structure becomes more coplanar.

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End to Edge (+/-)

FIGURE 4-2:Relationship between the ratio h2/H and the number of beams for different ratios of ri/ro. (Source: Chilton, Choo and Popovic, 1995; Popovic, 1996)

End to End (+/+) FIGURE 4-1: Reciprocal frame joint types (Source: Authors)

Further research was conducted which changed beam size, including span and radii when building reciprocal frames which helps better define the variation within these parameters (fig. 4-3). This research also focused on performance at various levels of variation and the extended consequences of those variations within the system of a self reliant RF form(O. P. Larsen, 2008).

FIGURE 4-4: Reciprocal unit height with piece thickness and connecting locations (Source: Authors)

We extrapolated on these principles in our own study and found that pieces that connect, or collide, with each other without any modification to reduce the center line to center distance (h2), as is mentioned in the introduction to this chapter, the key parameter defining the structural behavior of reciprocal frames becomes the radius of building pieces and where the PCP is located. Both of these directly affect the rise of the basic reciprocal unit, also known as the wrapping performance, when the units are aggregated to develop the structural frame.

We can get the function of vertical rise (H) on the piece thicknesses (r) and the connecting locations (L2/L) from the equation (1.1 - 1.10):

FIGURE 4-3: Parametric study combinations (Source: By Chris Dunn, O. P. Larsen, 2008)

If we take “k” for L2/L, the f(H) can be written as:

The graph (fig. 4-4) has a visual explanation of the change in increasing height that shows the relationship between the radius of the pieces and PCP distance. Within range, the larger the radius of wood pieces and the closer the connecting points are located, the quicker and heavier the arch can be formed by the frame system. Therefore, in defining the structural form within the integrated system, the computational parameters for curvature play a critical role.

Chapter 05 Joinery System

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RF Structure by Authors (Source: Daly, Tom)

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Joinery System Design Iteration

FIGURE 5-1:Custom harware for bamboo joinery system (Source: Youttananukorn, Pakphum)

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Our RF joinery system utilizes the naturally occurring stem void found in juvenile Paulownia tomentosa specimens through an additive 3D printed family of joints. Our research was grounded in traditional bamboo joinery systems. In particular, we found inspiration in designer Pakphum (Nanu) Youttananukorn’s Nanu x Bamboo Open DYI Bamboo Joinery System (fig. 5-1) Our design iteration process began through determining which RF connection (edge to edge, end to edge, and edge to edge) method best responded to the wood material which was also informed by or computational research. We used rhino to design a series of iterative joints and printed them on Stratasys Dimension ABS 3D Printer (fig. 5-2). Our experimentations demonstrated that an edge to edge connection joinery system could withstand the highest levels of force and accommodate the stem void inconsistencies within our material. Fig. 5-3 illustrates our final joint design.

Joint angle determined by angle of reciprocal unit

Material Testing

Dimensions of material thickness correspond with joint length

We conducted a series of material tests to determine the most effective joint material (fig. xx) We printed joints using the Stratasys Dimension ABS 3D Printer, Formlabs Form 3D printer, and Desktop metal 17-4 stainless steel printer. Out of these options, using engineering grade tough resin on the Formlabs Form 3D printer offered the highest levels of precision and material strength within the fastest time frame.

FIGURE 5-2:Original end to end 3D printed joint (Source: Authors)

In addition to 3D printing, we fabricated metal joints by rapid waterjet cutting and hand twisting to the desired angle. While this method allowed for the use of aluminum and stainless steel and was much faster than the Desktop Metal printer, we ultimately determined that 3D printing would provide more precise results and less margin for errors. This led us to select engineering grade tough resin as the material for our additive joinery system integrated with the natural stem voids in our wood material.

Joint fastens pieces together by hooking into the natural stem void

Developing a network of Joints

Our joinery system consisted of a digitally generated family of standardized joints that to define connections, adapt with material, and determine assembly guidelines. Each individual joint needed to respond to the materials within its RF unit including the thickness of the stem void and radius of the material.

The generation of the joints in grasshopper is generally to input two center lines and find the curve proximity to form a line-line curve to become the center support of the joint. After creating the planes that are perpendicular to the curve on the proximity points, the rectangle of the joint top and bottom can be determined, and the milling slots accordingly. Move the extruded rectangles (joint ends) and loft the shrunk rectangles for the center support. Make sure the center stick can be inserted into the slots. The only inputs are the lengths (measure the thickness of the stem void) and the number of pieces for labeling. These ensure that each joint is unique and precise to the connecting pieces.

FIGURE 5-3:Final joint prototype (Source: Authors)

We measured all of our materials, input the data into our grasshopper script, and printed the network of joints on the Formlabs Form 3D printer with the engineering grade tough resin.

FIGURE 5-4:Custom joint development (Source: Authors)

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Design goals Precise form design Low cost Quick production Ability to withstand force

Fabrication method 3D printing

Material PLA filament

7-14 stainless steel

Tough resin

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Water jet and hand twist

Aluminum

Stainless steel

FIGURE 5-5:Testing joint materials and methods (Source: Authors)

The Joinery System Digitally generated family of standardized joints to define connections, adapt with material and determine assembly guidelines.

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Material dimension and curve labeling customize joint

Center lines between piece connection point define direction of structure

Print tough resin angled joint

Generates twisted loft connection for 3D printer

Fabricate according to joint, slot and material labels

FIGURE 5-6:The network of additive joints (Source: Authors)

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FIGURE 5-7:Joinery system (Photograph Source: Daly, Tom)

Chapter 06 Form Finding and Structure Design

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RF Structure by Authors (Source: Authors)

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Number of Cull Out Parts

3 (Parts)

4 (Parts)

Min

2 (Parts)

a

Surface derive from the catalog

Hexagonized form not applicable

c

b

Size of the Openings

1 (Part)

e

37

g

f

Goal-driven tensile pavilion 2

Max

36

d

Goal-driven tensile pavilion 1

FIGURE 6-1: Structural surface catalog (left) FIGURE 6-2: Study models (right) (Source: Authors)

Based on the science exploration and all traditional practice of reciprocal buildings with the edge-to-edge connection, the output of the structure tends to form the shape of a dome.

(Hands-on Aided) Computational Form Finding Starting with the hemisphere created in rhino space, the grasshopper did a series of random cull outs on the surface to generate multiple different iterations of potential structural surfaces. The selected iterations of surface forms are laid out in the order of the increase of the number and size the openings (fig.

6-1).

And with the aid of the sketch models (fig. 6-2) for space making study and reciprocal structure understanding, we picked the forms that are similar to

them for further development.

Exploring Top-down Form Finding

Hand generate surface in rhino

The first set of attempts is to apply the reciprocal structural system to the desired surfaces. From the picked surfaces from the catalog to the manual build surfaces in rhino space, the iterations of reciprocated form structures using multiple techniques (kangaroo, karamba plug-ins) are arranged here (fig. 6-3 middle column).

While our designated units are a reciprocal structure with three wood pieces, and the essence of making a reciprocal frame is to convert the surface into a mesh and shift the list of mesh edges in a specific order.

To get a manageable reciprocal frame, the mesh polygons, or the list of lines to be shifted should be

FIGURE 6-3: Reciprocal structures by different techniques (Source: Authors)

Starting reciprocated sphere

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Subtraction 1

Subtraction 2

Subtraction 3

Subtraction 4

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FIGURE 6-5: Bottom-up form finding processes with hand model of final form (Source: Authors)

Create a mesh sphere and create desired reciprocal patterns on it

Bake the center lines and pipes for desired form element reduction

Bring to colliding file, assign each of the material piece certain radius Use the grab tool to move the piece to correct the reciprocation

FIGURE 6-4: Major grasshopper definitions for form finding (Source: Authors)

polygons with more than four edges. Thus we hexagonized the meshes by weaverbird components and sent the curves to regenerate the order and create the reciprocal structure (fig. 6-3 right column).

creating a mesh sphere, remesh it to get the evenly distributed triangles, convert the curves to hexagons and pentagons, generate reciprocal structure with thickness, and bake it for post subtraction processes. [image: iterations from subtraction of mesh sphere]

The result of the tests shows for the surface-generated structures, some unpredictable or irregular meshes are hard to manipulate for structures. And some derived from rhino-built surfaces had trouble achieving the right curvature when applying pieces with thickness.

Exploring Bottom-up Form Finding After the attempts at goal-oriented structure building, we shifted the thoughts of getting the form in an opposite way to create a reciprocal sphere first and then do element reduction. The steps are first

Final Structural Form The final structure form (fig. 6-7) is taking the iteration of “half-bridge” after all the transformations above and analysis of the structural stability. Then assigning different thickness categories to the center lines according to our material resources. Correct the reciprocal structure manually and do precise piece-to-piece collisions to each pair of wood pieces for further joints generation and milling slot making.

FIGURE 6-6: Major grasshopper definitions for post processes of colliding (Source: Authors)

Bake the center line for precise collision

Collide the pieces by pairs

Form Fact Height: 84.7 in Span: 83.3 in Number of pieces: 38 Number of joints: 65 Number of reciprocal units included: 19 Maximum piece length: 52.5 in Minimum piece length: 21.2 in

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FIGURE 6-7: Final structural from (Source: Authors)

Chapter 07 Fabrication

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Milling by Authors (Source: Authors)

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11/14 3pm rhino/ spreadsheet lengths TRUE confirmed TO CUTby JF and EBN

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FIGURE 7-1:Harvested Paulownia wood.

(Source: Authors)

1.5

21.16

22 5/8"

5/8"

5/8"

1

1.5

21.98

22 5/8"

1/2"

1/2"

3/8"

5

1.5

22.15

23 3/8"

3/8"

1/2"

3/8"

The wood was then meticulously measured and cataloged, sorting usable pieces into categories of average diameter between one and four inches in diameter. This catalog was cross referenced and then integrated with the design of the structural form.

The dimensions were regularly assessed to build in tolerances for the irregularity in the material, while changes were made to the design and the wood was cut to the specified length for its unique placement within the overall structure. The final structure has 38 pieces of wood each with unique dimensions.

1/2"

knot on

6

1

25.19

26 2/8"

3/8"

1/4"

1/4"

11

1

26.09

27 1/2"

3/8"

1/8"

3/8"

knots b

7

1.5

28.63

29 3/8"

1/2"

3/8"

3/8"

small k

27

3

28.66

29 7/8"

1 5/8"

3/4"

1 1/4" 1/8"

8

1

28.94

29 1/2"

1/4"

3/8"

4

1.5

29.14

30 1/2"

3/8"

1/2"

1/4"

knot on

12

1.5

29.51

30 3/4"

1/2"

3/8"?

3/4"

knots o

2

1

30.83

31 1/2"

3/8"

3/8"

3/8"

10

1

31.73

32 3/8"

3/8"

3/8"

1/4"

13

1.5

31.94

32 3/8"?

5/8"

3/8"

1/2"

15

1.5

32

32.5 3/8"

1/2"

1/2"

3/8"

17

2

32

33 1/2"

5/8"

1/2"

5/8"

23

1

32.77

33 3/8"

3/8"

1/4"

3/8"

37

2.5

33

32.5 3/4"

1"

5/8"

3/4"

5/8"

3/4"

1"

1"

1/2"

3/4"

30

3

33

32.5 3/4"

19

2.5

33.19

34 5/8"

small k

bar join

45

16 2 (go down to 1.5)33.69

34 5/8"

5/8"

5/8"

7/8"

small k

21

2

33.75

34 1/4"

1"

1/4"

3/4"

bar join

14

1.5

34.86

35 5/8"

3/8"

5/8"

1/4"

38

1

35.96

36 3/8"

3/8"

3/8"

1/4"

knot on

9

1

36.13

37 1/4"

1/2"

1/4"

3/8"

all knot

32

2.5

36.66

37 1/2"

1 3/8"

1/2"?

1"

knot on

29

2.5

37.85

38 1/2"

1 1/4"

1/4"

1 1/4"

A and B

18

2

38

38 3/8"

1"

1/2"?

5/8"

knot on

22

1.5

38.51

39 3/4"

1/4"

7/8"

1/2"

28

2.5

39

39 1/4"?

1 3/8"

1/2"

7/8"

25

2.5

39.18

40 7/8"

5/8"

1"

1/2'

26

3

39.34

40 7/8"

1/4"

7/8"

1 1/8"

knot on

33

3

39.91

40 3/8"

1 3/4"

3/8"

1 3/8"

both en

20

2

40

40 7/8"

3/4"

1/2"

5/8"

knot on

24

1.5

41

41 1/4"

3/4"

1/4"

1/2"

bar join

35

1.5

44.91

45 1/2"

3/4"

1/4"?

5/8"

may ne 35 very

34

3

45

45 3/4"

1 5/8"

3/4"

1"

end A s

31

3

51.21

52 3/4'

1"

7/8"

1 1/4"

knot on

36

1.5

52.53

53 5/8"

1/2"

1/2"

1/2"

1321.33 FIGURE 7-2:Working dimensional spreadsheet.

Authors) Number (Source: Diameter 1.25 length rounded length

Material Sourcing and Processing Our method of structural form finding is highly integrated with and dependent upon the material harvested. The quantity and quality of Paulownia wood we gathered was constantly being assessed in conjunction with that process. The characteristics of the harvestable material would dictate much of what we could achieve in our final structural form. Ultimately, we harvested almost two-hundred feet of viable Paulownia wood from three main sites in the surrounding area. After felling the trees and removing branches, the wood was cut into the largest manageable pieces for transport.

3

stem void

bar like

large sv-e dist. stem void

large sv-e dist. notes

A

B

12’ 10’ 8’ 6’

46

4’

47

2’

Harvest FIGURE 7-3:Cataloging and processing Paulownia wood.

(Source: Authors)

Cut pieces by hand to specified lengths

Mill with Kuka

Post process with kuka

File and assemble by hand

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FIGURE 7-4:Digital model with mill slots determined by Grasshopper script.

(Source: Authors)

Robotic Milling With the material cut to its specified length, custom slots were milled using the KUKA robotic arms at each PCP to give the the 3D printed joints access to the stem voids and define the angle of connection between each piece with precision relative to itself and other pieces. KUKAprc mill files were derived from the integrated grasshopper model using Fusion 360 to define the mill paths. Each piece would have one or two mill files depending on the geometric demands of the five access milling which helped provide tolerances within the processing of the irregular material and controlled the simplified 180

degree rotation between mills. This process accounted for changes in diameter across each piece due to the natural tapering of the wood material and the effect that would have on the connection between each piece, to define the custom slots to be milled.

Further irregularities in the material were assessed while milling and if necessary the operability of the robotic arm was used as a means of post processing.

FIGURE 7-5:Milling process and material result - Slots are milled according to Fusion 360 and Kuka prc outputs. Flip 180 degrees to mill other side and post process by robot as needed. Then label for assembly.

Determine form

Print joints

Process wood

Assemble system

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FIGURE 7-6:Overview of design fabrication process (Source: Authors)

Assembly Assembly of the structure with mass customization relied on detailed labeling to connect individual pieces and joints which was baked into the original process for fabrication, labeling Individual pieces by hand and connecting those with labeled joints. Basic units derived from rhino model made up of three pieces of wood and three connection joints were prefabricated before taking them into the field to build the final structure on site where it would lean against a large tree, integrating back into the landscape. Building from base of structure to top where a larger paulownia piece was lashed to the tree. Stabilize structure with zip ties to account for shear force and movement during assembly, the base units were anchored into the ground with metal five metal rods

and the units were added one by one while carefully monitoring the affects of the additional load as each piece in each unit relies and balanced on the others. Once all of the connections were established the structure became stable and the zip ties were removed carefully allowing pieces to simply reciprocate within the complex structure.

FIGURE 7-7:Key moments of assembly (Source: Authors)

Chapter 08 Outlook

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RF Structure interior (Source: Authors)

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FIGURE 8-1:As bulit laser point cloud scan data of installation.

(Source: Authors)

FIGURE 8-2 and 8-3: As bulit scan data. Structural and site plans.

(Source: Authors)

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FIGURE 8-4:As bulit scan data.

(Source: Authors)

Outlook and Conclusion

This project expands upon existing research and moves the systems of material intelligence and computational design for RF structures forward using advanced technologies. Continuations of this work should look to better integrate fabrication plans in physical space to decipher the most efficient and precise method of assembly for the complex interrelated system. Since the reciprocal structure relies on the two connection points that need to be correct across the entire system, which was not completely straight forward to assemble allowing for movement. Also, failure of the 3D printed joinery system due to movement and variation in the final installation form the precise definition where the piece would not stay in place correctly in the void. While inconsistencies

of materials made it difficult to create a flexible custom joint, having the angle and label was extremely useful and, in a way, they ended up serving as a form of scaffolding to help with ease of installation. Continuations of the work could look to further integrate the designed and fabricated work using weight simulations and Hololens augmented reality glasses to achieve greater precision with adaptable means of fabricating. Nonetheless, the advancements in reciprocal frame computational design and the opportunities for the use of invasive species as space shaping elements, made possible by intelligent design and fabrication tools bring exciting futures to life.

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References

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References Apolinarska, A. A. (2018). Complex timber structures from simple elements: Computational design of novel bar structures for robotic fabrication and assembly. https://doi.org/10.3929/ETHZB-000266723 Flying cloud reciprocal roof timber frame. (n.d.). Retrieved September 24, 2020, from https://timberhomesllc.com/our-work/timberframes/flying-cloud-reciprocal-roof-frame/ Invasive species. (n.d.). National Wildlife Federation. Retrieved December 6, 2020, from https://www.nwf.org/Home/EducationalResources/Wildlife-Guide/Threats-to-Wildlife/Invasive-Species Material misbehavior. (n.d.). After Architecture. Retrieved September 21, 2020, from https://after-architecture.com/materialmisbehavior 60

“Lamella Flock.” Royal Danish Academy, 20 July 2010, https://royaldanishacademy.com/case/lamella-flock.

Mostafavi, Sina; Kastrati, Valmir; Badr, Hossam; Malan, Shazwan.

Design Computation to Robotic Production Methods for Reciprocal Tessellation of Free-form Timber Structures: Design, production and assembly of 100 years Bauhaus wood Pavilion. Retrieved 2020 from http://papers.cumincad.org/data/works/att/ecaade2020_468.pdf Nanu x Bamboo 1.0 - Republic Nanu. https://republicnanu.net/Nanux-Bamboo-1-0. Accessed 17 Oct. 2020.

Paulownia tomentosa. (n.d.). Retrieved September 23, 2020, from https://www.fs.fed.us/database/feis/plants/tree/pautom/all.html Pizzigoni, Attilio. LEONARDO & THE RECIPROCAL STRUCTURES. University of Bergamo, http://www.pizzigoni.it/leonardo%20Eng.pdf.

Accessed 23 Sept. 2020.

Popovic Larsen, Olga. RECIPROCAL FRAME ARCHITECTURE. 2008.

Architectural Press is an imprint of Elsevier, 2008, https://casaeco. files.wordpress.com/2012/03/reciprocal-frame-architecture.pdf.

Popovic Larsen, O. (2014). Reciprocal frame (Rf) structures: Real and exploratory. Nexus Network Journal, 16(1), 119–134. https://doi. org/10.1007/s00004-014-0181-0

Reciprocal roof. (n.d.). Retrieved September 24, 2020, from https:// danielsiepman.nl/en/reciprocal-roof/ Rippmann, M. (2016). Funicular Shell Design: Geometric approaches to form finding and fabrication of discrete funicular structures [ETH Zurich]. https://doi.org/10.3929/ETHZ-A-010656780 Ryuboku hut (Okishima island, Japan) – design spectrum. (n.d.).

Retrieved December 9, 2020, from https://www.designspectrum.hk/ project/ryuboku-hut-okishima-island-japan/ Vrontissi, Maria, Thoennissen, Udo. Full-scale design explorations in architecture education: small-scale reciprocal structures for outdoor use. 2015/09/20. https://www.researchgate.net/publication/284182716_Full-scale_design_explorations_in_architecture_ education_small-scale_reciprocal_structures_for_outdoor_use

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Acknowledgements

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Thank you to everyone who has helped make our project possible through your time, ideas, feedback and assistance! We are so grateful for your support.

Ehsan Baharlou Melissa Goldman Trevor Kemp Gabriele Rausse Our LAR 8010 Classmates

Living materials (Top source: Authors Bottom source: Daly, Tom)

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