ASSEMBLY OF FLEXIBLE TIMBER STRUCTURES WITH ISOTROPIC INLAY

1 Research Topic
2 Framework
3 Scientific Interest
4 Research Aim & Objectives + Methodology
5 Bibliography


1 – Research Topic

/Statement
This research explores wood assemblies that yield more fluidly when confronted with external environmental  forces such as ice, water, snow etc.
Can this performance be achieved through a soft-body joint and provide alternative solutions  to current rural practices in Norway, particularly concerned with footbridges.
Hybrid: In this case the combination of wood and silicone. It does not hide the fact that it is a heterogeneous product of the two, it rather becomes a new form-language.

/Issue – wood assemblies
Advancements in wood related sciences have led to the breeding of competitive structures used in multi-scale applications. While engineered wood is inevitably a product composed of many, it seems to be reinstated as a singular element in construction. For example, CLT is strengthened timber, enabling a whole new spectrum of positions it couldn’t otherwise obtain. As a building- block, however, it is not performing any different than a piece of lumber. What will happen when wood only defines one part of the block – can block logic become agent for new arrays of form in timber industry?

/Target – footbridges
Remote situated structures, such as footbridges, tends to be product of local vernacular practice.
In Scandinavia, these have historically served as important utilitary devices for access and traverse in rural areas, but does also make appearances in the city due to varied and challenging geography. Their complexity is established by the significance of land at a certain extreme,
often resulting in a static solution most ideal for only a specific point in time.

/What – external forces
Referring to extreme weather causing damage on structures in nordic climate (flood, snow, ice). Also understood as an applied force decreasing structural health. When a bridge is suffering from heavy-impact its elements either fall out of position, crack or deform. Rural communities is prone to deal with these conditions on a seasonal basis – where land damages can extend into a chain of events tearing on existing infrastructure. Although periodic, it is difficult to predict exactly how natural forces will play out.

/How – soft-body joints
A strategy to work with joint behavior in high-impact environments.
Like a knee-joint, it is defined by two or more surfaces buffered by a flexible membrane.
Joint will have to prove its ability to absorb shock and low-rate damage within a defined domain. This work acknowledges similar approaches found in large bridge constructions. However, there is a novelty in scale – introducing different criterias explored in the making of hand cut joinery.
In the beginning stages, silicone will be placeholder, primarily due to its robustness and approachability, combined with the shielding-effect it has on its neighboring parts.
There is an opportunity towards the end to speculate on system’s-scalability.


2 – Framework

/Sources
1. Footbridges: Norwegian + (Intergov.) reports
Incl.:“Norsk Klimaservicesenter (Norwegian Climate Center)”, “Bruprosjektering (Rules and Standards for Timber Bridges in Norway – by Norwegian Public Roads Administrations)”, Norwegian Natural Perils Pool”, and “Norwegian Institute of Wood Technology”

  • Scale related building assemblies used in construction (to be understood in comparison with the system I’m developing)
  • Material specs
  • Damage reports (geographic data + cost-estimates)
  • Climatic overviews and forecasts

2. Handbook: Timber Structures (EU)
Leonardo da Vinci (Euopean) pilot projects 

  • Structural timber + wood properties
  • For cross examination purposes (comparing data)
  • Ultimate states: joints
  • Spatial timbers const. + timber bridges

 

/Researches
1. Integrating Material Performance
Tom Svilans – CITA 

  • Understanding key aspects of design innovation
  • His interpretations of where the wood industry is heading
  • The related digital technologies and workflows involved
  • Constraints of wood
  • Current misconceptions of wood (dogmas)
  • Micro-scale vs macro-scale (ways of approaching the development of wood)


2. Wood Urbanism: From the molecular to the territorial
By Daniel Ibañez, Jane Hutton and Kiel Moe

  • Lifecycle of wood
  • Strategies of managing resources
  • Short term and long-term effects
  • Wood as sustainable resource

3. Rethinking Wood – Future Dimensions of Timber Assembly*
Ed. by Hudert, Markus / Pfeiffer, Sven (2019)

  • Spatial Timber Assemblies
  • Joints for Robotic Assemblies
  • Living / Organic Joints + Flexibility
  • Contemporary robotic workflows

 

3 – State of the Art

/Timber as heavy-duty structure
Advancements in wood related sciences like cross-laminated timber (CLT) technologies have led to competitive structures enabling benchmark projects such as the world’s highest standing timber framed building at 49 meters in Bergen, Norway (Kleppe, 2018). Key reflections from this project highlights a longer development phase embedded in material sciences and emphasizes on wood as future building material.

/Free-form enabled geometries
Recent work done on free-form glulam structures (Svilans, 2018) quantifies the complexity of wood as input for fabrication steps in order to obtain desired geometries. Until now, this workflow has not yet been integrated with contemporary practice. There seems to be a strong effort in accelerating glulam technologies for use in multi-scale applications as its previous geometrical restrictions have faded.

/Low-range flexibility in civil bridges
Utilizing timber as a dynamic element have proven to be a challenging matter.
To some extent this has been limited to the conception of wood as a fragile and soft material.
In 1990, The Norwegian Public Road Administration put forward an initiative to extend the use of timber in civil architecture, resulting in a total of 300 bridges and pioneer projects (Trefokus, 2007). Some of them were set to be composite bridges of steel and timber (Kolbein, 2008). In which case glulam and CLTs members were deployed as main structure, fixed by metal connections to concrete decking. While proposed as a lightweight alternative to steel with good dynamic behaviour during loading, when compared with a rope suspension bridge the flexibility spectrum is considerably small. Bridges of large scales are of course due to follow strict regulations. However, in high-rise constructions you can feel the building sway in the wind. This is not desirable and therefore kept as low as possible, but this provides a good example of a flexible structure in architecture today.

/Experimental joint-structures
As part of SUTD-MIT International Design Center (Kaijima, 2017) – a new interlocking structure was proposed in response to traditional locked structures. Implementing scissor-like joints capable of retracting – turning the entire structure into a completely foldable system. Geometry based joints.

/Contemporary furniture design
Experimental furniture design explores wood-modules held together by heat-shrunk plastic bottles.
This novel research offers ways of appropriating wood to work with other materials, previously perceived as non-structural, hence giving rise to stable, scale-specific assemblies (Pedros, 2016).‘Plastic Nature’ is another furniture series injecting silicone into wood, as strategy to geometry based interlocking systems as opposed to connector relient joints (working with bolts, screws etc.). Silicone as structural binder and infill, introduces new flexibility and use in furniture (Pelidesign, 2007).

 

4 – Scientific Interest


/On constrution
Todays architectural practice is challenged by new technologies and population growth.
Our cities have become place and process for complex scenarios of contemporary urbanization (Ibañez, 2018). This facilitates densely intertwined urban fabric, stitched together by materials favoured by urgency, readiness and deployability, causing high impact on land and resources. As cities are growing, the need for a circular sustainable model in construction industry could not be rushed more.

/Wood alternative
On the other hand, wood is effortfully pushed as runner-up alternative to other heavy-duty structures. So far it has marked its entry in construction as the only grown structure, hence accompanied with a remarkably low environmental-impact. Arguably becoming a preferred element in construction, particularly in the nordic countries, due to its availability and rooted forestry traditions. Recent projects of wood has benchmarked a 49 meter tall timber framed building enabled by CLT and glulam-members (Kleppe, 2018). Still, wood is perceived as a fragile element in construction foreshadowed by steel and concrete lobbies, hence postponing any immediate applications.

/Flexibility
The scalar properties of wood, stresses a new line of research on wood specific construction tasks. Until now, we have seen that wood can be reinstated as a rigid and stable structure. We also know that wood is inherently flexible, having inspired glulam and similar technologies. Despite this, there has not been further effort in pairing wood with its native characteristics as tree. As tree, it is arguably isotropic due to its multi directional fibre orientation and performs well in forceful-environments. Can scale-related techniques bring forward new flexibility in wood and accelerate it as low-impact material in construction?

 

5 – Research Aim & Objectives + Methodology

 

/Hypothesis
Formal wood-explorations in small scale infrastructure
While current practice appropriates timber as low-range flexible member, furniture applications has proven wood to be operative in moving, high-impact environments, when put in context with a soft-body membrane or counterpart. These are examples that benefits from joints explored formally through geometry as opposed to connector relient geometries and superimposed fixtures having dominated our practice until now.

 

“Can research on wood and soft inlay advance beyond the furniture-scale, and further, negotiate new structural assemblies with a higher degree of flexibility?”

/Objectives
1. Definitions:

  • Simple Joint – Creating a joint within the same element (subtractive manufac.)
  • Joint – Two pieces connected by a flexible soft material.
  • nJoints – Three or more pieces connected by a flexible soft material.

2. Sub-objectives:

  • Obj.1 To parametrize joint variations.
  • Obj.2 To analyze structural behaviour of joint.
  • Obj.3 To link structural behaviour with parameter variables.

3. End-objective:

  • To create a structure from joints and nJoints


/Methodology

1. Prior to the research it is necessary to classify the different components:

  • A – the hard/flexible component (wood)
  • B – the soft/elastic component (ex. silicone)

2. Project overview:
[Structure > Element > Joint] or [Macro > Meso > Micro]

  • Structure:
    Overall composition of elements.
  • Element:
    Made of component A and B.
  • Joint:
    Threshold within an element where A meets B (interface).

3. Research stages:

  • Stage 1 : Manual joints, done with a dozuki hand saw accompanied with traditional carpentry tools.
  • Stage 2 : 3-axis joints done with cnc machine operations.
  • Stage 3 : 5-axis joints done with robotic-arm.


/Obj. 1 – Joint Parameters:
(Relates to wood element [A])

In order to make these joints, it is important that every potential variable is identified as a parameter. For the purpose of stage 2, the aim will be to test flexibility within one element through subtractive manufacturing, hence working with a simple joint.

(Piece refers to stock of A)
(Bridge refers to the binding element connecting two elements)

  1. Piece length – length of stock
  2. Piece width – width of stock
  3. Piece depth – depth of stock

  4. Split parameter – location of joint

  5. Bridge gap – distance to span
  6. Bridge width – thickness
  7. Bridge position – location of bridge (ex. 0.5/1.0 – centered)
  8. Micro geometry – interface between materials


/Obj. 2 – Structural Test

  1. Extract deformation value for each joint instance.
  2. Use a grid to evaluate and measure amount of deformation for each instance.
  3. Possibility to apply loading (equal) to see maximum capacity for each instance

 

Obj. 3 – To link structural behaviour with parameter variables

– Feedback of numeric data (mm precision) to joint parameters.
Once all instances are linked with corresponding performance, one can begin to construct an overall composition working with the range of flexible performances available.

– Furthering the natural behaviour of timber through inlays like silicone (B) (a soft material counteracting upon wood) is improving its ability to withstand applied forces in high-impact environments.

– The use of flexible, potentially isotropic materials, as counterpart is key to negotiate the behaviour of timber when suffering from external forces. This two-way relationship can be seen as a more formal (formal as in form) exploratory research working with not one set of behaviours, but two, in order source new geometries of timber.

 

5 – Bibliography

[1] Ibañez,D. (2018). Wood Urbanism: From the Molecular to the Territorial.
Boston, Harvard GSD

[2] Kleppe,O. (2018). Treet – info in english – BOB [online]

Available at:

https://bob.no/treet/treet-info-in-english

[Accessed 16.Nov.2018].

[3] Svilans, T., Poinet, P., Tamke, M. and Thomsen, M. (2018). A Multi-scalar Approach for the Modelling and Fabrication of Free-Form Glue-Laminated Timber Structures. [online] ResearchGate. Available at:

https://www.researchgate.net/publication/319859058_A_Multi-scalar_Approach_for_the_Modelling_and_Fabrication_of_Free-Form_Glue-Laminated_Timber_Structures

[Accessed 16 Nov. 2018].

[4] Trekfous (2007). Fokus på tre: Broer i tre. [online] Trefokus.no Available at:

http://www.trefokus.no/resources/filer/fokus-pa-tre/12-Broer-i-tre.pdf

[Accessed 16 Nov. 2018].

[5] A. B. Kolbein (2008) Leonardo da Vinci Pilot Projects: Handbook 1 – Timber Structures, Ch. 15, Timber Bridges, p 224 – 225

[6] Oyler, D. and Wu, J. (2018). Oyler Wu Collaborative | INFO – Active Inlay Studies. [online] Oylerwu.com. Available at:

https://www.oylerwu.com/info-active-inlay-studies

[Accessed 16 Nov. 2018].
—
Assembly of Flexible Timber Structures with Isotropic Inlay (written part) is a project of IaaC, Institute for Advanced Architecture of Catalonia developed at the Masters in Advanced Architecture in 2018 by:

Student: Lars Erik Elseth
Faculty: Mathilde Marengo