Investigating Lichen Growth Systems to “Grow” Timber Structures

from Investigating Lichen Growth Systems to “Grow” Timber Structures

Investigating lichen growth sytems to “grow” secondary timber structures foruse in church restoration

Digital Design thesis by Zimmie Sutcliffe

Advanced Digital Design Techniques (AR7043)Taught by Arrash Fakouri & Georgios Tsakiridis

Fig 4. Adding divide curve command to seperate line into segments with a series of points along a line

Fig 7. Previous script in full - Using Series & Polygon parameters to control number of sides, position & size of polygons

Fig 5. Above script in full - number slider to control number of points on line & graftingFig 8. Using Rotate parameter to control the rotation of polygons and create a twisting effect

Fig 6. Creating a series of polygons based on points already established on the line

Fig 9. Above script in full

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Romney Marsh

The setting for my investigation is based in Romney marsh in Kent. The marsh is home to a series of historic churches, owned by the Romney Marsh Historic Churches Trust. As part of my work in Unit 14 with Pierre & Pereen D’Avoine we took a trip to study these churches. The church I was given to survey was St. Augustine’s Church in the hamlet of Snave.

Situated on marsh land, the church has sunk & twisted over time, distorting its plan and height. This process has been gradual over centuries but the church is now very uneven, which could lead to significant structural issues over time. Fixing these problems would be very costly, probably too costly for the trust, meaning this great church could cease to be a functional place of worship for the first time in 800 years.

It is in light of this that I began thinking of ways in which digital design & cutting edge techniques could respond to this challenge. Church restoration is an issue faced across the western world due to the deterioration of these wonderful but incredibly old buildings & the declining role of the Church in society making financing maintenance and repair more difficult. Nowhere is this more evident than in the tragic fire at Notre-Dame in April 2019. The cost of rebuilding has been estimated at 600 million to 1 billion Euros.

The shifting ground level can be seen here

St. Augustine’s Church - viewed from West sideButtressing to maintain stability in shifting marsh land

The misalignment of the two arches shows how the building has moved10 11

St. Augustine’s Church, Snave - Ground Floor PlanSectional elevations

1:100 @ A31:100 @ A3

1. Fireplace

22. Piscina

3. Pulpit

4. Seating

5. Font

Chapel

Chancel6. Ancient font

7. Piano

8. Altar

9. Sedilia

Nave4

Porch(Disused)

Tower(3 bells)

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Photogrammetry Test

I produced a series of partially successful photogrammetry test models using Recap Photo after returning to St. Augustine’s Church to conduct an exterior photo survey. Below documents the process I went through to do this and some of the results I achieved. Unfortunately, this phase of the investigation didn’t produce the results I had hoped but it was still informative learning the process and software involved in producing photogrammetry models.

Fig 3. Photogrammetry study of north facade

Fig 1. Transferring photos from PC into Autodesk Recap Photo

Fig 4. Photogrammetry study of south facade

Fig 2. Uploading the project to the cloud for construction

Fig 5. Photogrammetry close up study of West tower

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Lichen growth - St. Augustine’s @ Snave

Growth patterns of lichen

“The string rewriting language of L-systems provides a framework for creating strikingly realistic geometric models of plants and trees. Parametric L-systems incorporate continuous attributes and allow more sophisticated simulations of plant development. Earlier work on plant development...incorporates interaction with the environment but in a different context than L-systems. The “environment-sensitive automata” uses ray casting to test for intersections and proximity so that simulated plants avoid obstacles. Several researchers have proposed mathematical models directly related to lichen growth, but these models are quite simplistic from the point of view of morphogenesis.

In cluster growth models, a cluster gradually expands into its surrounding medium. The cluster is given some initial shape, and expansion occurs based on an aggregation algorithm. Simple algorithms often generate complex structures that resemble certain types of morphologies. Witten and Sander proposed a cluster growth model called diffusion-limited aggregation (DLA) that simulates diffusion using random movements of particles. Kaandorp used an accretive growth model to simulate three-dimensional formation of corals and sponges. In this iterative model, layers of materials are added to a growing tip. The thickness of the layer can be parametrized such that more growth occurs at the tip than along the sides. If this process is tuned properly, it can result in branching patterns that resemble corals and sponges.

A lichen consists of a fungus and an alga living together in a symbiotic relationship. The fungus lichen consists of a fungus and an alga living together in a symbiotic relationship. The fungus is the visible part of the lichen, while the algae form a thin green layer just under the surface. The fungus provides a physical structure that captures minerals for the algae and protects it from desiccation. The algae, in turn, generate food through photosynthesis for the fungus. This relationship allows the lichen to survive and grow in habitats that neither symbiotic partner could exist in alone. Lichen are divided into three morphological groups: crustose, foliose, and fruticose. Fruticose lichen are shrub-like and stand out from the surface of the substrate. Since fruticose lichen are structurally similar to plants, their form is a good candidate for a structure-oriented model such as L-systems.” (Walker Sumner, R. (2001)

A series of images showing the extent & different types oflichen growth on grave stones in the church yard

The three types of lichen

Internal structure of lichen

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Crustose lichenFruticose lichen

Foliose lichen

Fruticose lichen

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Agri Chapel

Momoeda Yu Architecture Office - Nagasaki, 2016

Billed as a new Gothic style chapel, this project uses a fractal system to create a pendentive dome using timber structures resembling trees. This minimises the amount of columns on the ground, increasing floor space for church goers.

The fractal system is an example of using a mathematical growth structure to create an efficient structural solution that would likely not have been implemented, instead a more conventional structural grid would probably have been chosen. The images below show the beautiful patterns created by the overlapping geometry and the mathematical rationale behind the design of the system. The image to the bottom right demonstrates how digital design was used to test for buckling in the structure and ensure its safety.

Although a fairly simple example, this kind of growth system mimickingis what I wish to explore in more complexity in this report.

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Initial sketches

Lichen growth formulas

To begin the process of translating the vision in my mind into a workable design strategy I produced a series of rough sketches aiming to deduce the location and form of the structures I want to produce in Grasshopper.

The sketch to the right is my initial vision for “tree like” timber structures to support the building externally, acting as additional buttressing against sinking and twisting. How these would attach to the existing structure and where I would attempt to resolve in Grasshopper.

Below sketches show my strategy for supporting structures internally. Using the principles of DLA I intend to create a bounding grid based on the existing church layout and insert slender timber columns at the centre of these grids from which a timber canopy would “grow” until it connects with the existing walls. This gives a highly random, intricate web pattern of slender elements.

Organisms grow according to a number of patterns and systems, influenced by a multitude of factors including sunlight, moisture, space, ability to form symbiotic relationships with other organisms etc. Much scientific literature aims to analyse and understand these systems & I have documented the basic principles of some here.

My growth system will be based on a version of diffuse limited aggregation (DLA) which creates random branching patterns within a bounding area. There are many examples of people modelling organisms such as algae, coral, snowflakes etc using forms of DLA algorithms, which I have studied and taken elements from.

The sketch below left shows the points of structural strength and weaknessin the building currently, and strategically where to locate the newsecondary structures.

Algae growth system diagramFractal growth - as seen in Agri Chapel

Laplacian growth equation

Diagram showing DLA process

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Final modelling

I imported an existing CAD drawing I had done of the Church and grouped the sections of solid wall in the plan.

To place the columns I copied the grid to ground level in order to extrude the column footprint up to the level of the original grid.

I then extruded each of these surfaces up to the height of the eaves, roughly 3.3m. Next, I drew rectangles to form a grid, with corners at the centre lines of existing walls.

Fig 1. Creating a grid framework using existing structure

Fig 2. Using grid rectangles to locate new columns

The plan to the left shows the final division of the building into a series of grid squares based on the unconventionally aligned existing walls.

I have located the centre of these rectangles to form the points for new timber columns.

The grid connecting the existing loading points in the structure is located at the height of the eaves line as this is the level at which the new branching structure will be place to provide stiffening without compromising movement through the space.

Fig 4. Replicating the grid at floor level

Fig 5. Final column layout

This screenshot shows the 7 new columns formed using the grid layout, with 3 aligned down the centre of the nave and 4 in the chancel & chapel forming an inner ring that echoes the existing grid of buttresses and walls.

As the columns are slender their positioning should not impair movement in the church, being strategically placed.

This image shows better the relationship of the new secondary timber column grid to the existing walls, providing a complementary yet alternate rhythm to enhance the space.

Fig 3. Final suspended grid layout

Fig 6. Relationship of old and new structures

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Having built the grid system, I next began preparing my model for the Grasshopper phase of the design.

Adding points at the intersections of columns allowed a consistent base for the algorithm to work from in each grid square.

Fig 7. Adding points to columns as basis for DLA acretion

Fig 10. Base church structure modelled in Rhino

The DLA process is intended to run with the same settings and base points for each section of the grid, allowing the algorithm to produce unique results for each square within a consistent framework.

The hope is this framework will provide a series of beautiful, unique geometries that share the same language and core elements.

Fig 8. A series of points at the centre of a grid square form the basis of the “growth”Fig 11. Base church structure with new columns

The next stage was to load the Grasshopper script. The algorithm is fairly simple, with 4 sliders to control the output and manipulate this.

The points placed on top of the column act as the seed points from which to grow the branches within the circular boundary.

Fig 9. Running the DLA script on column 1

Fig 12. Base church structure with columns and final branch forms generated by DLA script

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Re-creating Grasshopper script

To build my DLA script I used a script written by a third party and spent a while manipulating the parameters of this script to understand the function of each component and how the script had been built up. I then attempted to rebuild a similar script from scratch, beginning with a VB script component that I added additional inputs and outputs to.

Fig 13. New lichen growth inspired structure generated in Rhino & Grasshopper

Fig 1. Beginning with a VB script to enable me to plug in the number & type of parameters I want

Next I created the number of additional inputs and outputs I needed based on the parameters I wanted to be able to manipulate when growing my geometry. I then named each parameter based on its function.

Fig 14. Results of DLA script processFig 2. Naming the inputs and outputs

The first step in generating geometry was to give the VB script a series of seed points from which to start the DLA process. By adding a point button and right clicking to add multiple points I could then simply select the points I placed on the columns through Rhino.