Coralline algae are red algae which are characterized by hard thallus, an undiffrentiated vegetative tissue which displays calcerous deposits within the cell walls. They can be find in marine waters all over the world. This plant plays an important role in the ecology of coral reefs. There are plenty of species that feed on them. Coralline algea usually grow at the surface of the rocks, but also on other algae, animals or even as a parasite of other corallines.


Coralline algae

Corallines are divided into two groups:
– The non-geniculate (non-articulated) corallines, which are basically a thick layer of crust (few micormeters to several centimeters)
– The geniculate (articulated) corallinesm branching, tree-like organisms. They are attached to the substratum by crustose. It means that the algae grows tightly appressed to it’s base.


Coralline algae, geniculum and intergeniculum

Algae usually grow in low-intertidals, wave exposed habitats, and obviously, as a sessile organisms, cannot to escape bad environmental conditions such as strong and big waves. They must endure theirs impact wherever they settle and grow.

Their high flexibility helps them resist wave-induced forces despite their hard tissues. This is due to the articulated structure of the plant, which according to the fossil record, evolved about 100 milion years ago. Longer, calcified sections (intergenicula) are separated by noncalcified joints (genicula), which give flexibility to the fronds. Geniculum size and breaking force vary predictably along articulated fronds. As fronds grow, genicula get bigger and their tissue strengthens. At the bases of fronds, where the biggest support is needed, the strongest genicula are positioned. Near the tips, where the smallest branches are, the genicula are weaker. It is build in the way that keeps optimal genicular morphology which maximizes flexibility while minimizing stress amplification. Each unit is exactly as strong as it needs to be, what allows to avoid wastes in energy or materials. This rule corresponds to the engineering theory of optimal design.


Coralline algae, branches

This evolutionary innovation allowed coralline algae to grow away from it’s base and resist hydrodynamic, wave-induced forces. It allows the plant t survive and prevent it from breaking easily even in hydrodynamically stressful conditions.  Segmentation affects the bending performance and amplifies bending stresses within geniluca. Algae’s flexibility gives it the abitility to ‘go with the flow’ limiting drag forces. It allows reconfigurations into more streamlined shapes. It reduces thallus area that is projected into rapid flow by bending over into slower moving water.


Coralline algae, flexibility



Other reference to articulation we can find in our own body, in the connections made between bones. These joints are constructed to allow for different types and degrees of movement. They are cassified stucturally, which determines how the bones connect each other and functionally, by the degree of movement between the articulating bones. In practice, these two types of classification overlap significantly.

Looking at the functional (movement) classification there are:

1. Synarthrosis – little or no mobility
2. Amphiarthrosis – slight mobility
3. Synovial joints – freely movable

Movable joints are also classified and that is according to the type of movement they allow.
There are:

– Plane joints
– Hinge joint
– Ball-and-Socket joint
– Saddle joint
– Pivot joint
– Ellipsoid joint


1 – plane joint; 2- hinge joint; 3- ball-and-socket joint; 4- saddle joint; 5- pivot joint; 6- ellipsoid joint



Articulation refers to the manner in which the surfaces or forms come together to define its shape and volume. Each articulated structure reveals the precise nature of its elements and their relationship to each other and to the whole. In Art and architecture it is a method of styling the joints. Through degrees of articulation it is possible to get many varying types of joining, from exceptionally distinct to fluid and continous.

There are several uses in articulation in art and architecture:
– movemenet and circulation
– uses and accessibility
– sequance and succession
– symbolism and meaning


1- movement and circulation ,Telestra Dome; 2-uses and accessibility, Forbidden Palace; 3 – sequance and succession, Mezquita; 4- symbolism and meaning, Sydney Opera House


Articulation of forms

1. Differantiation adjoining planes with a change in material, color, texture or pattern
2. Lightening the form to create sharp distinctions of light and dark at its corners.
3. Developing corners as distinct linear elemetns independent of the surfaces
4. Removing corners to physically separate adjacent planes


Articulation of surfaces

1. A distinct contrast between the surface colour of a plane.
2. A frontal view reveals the true shape of a plane’s oblique views distor it
3. Elements of known size within the visual context of a plane can aid our perception of its size and scale
4. Texture and colour together affect the visual weight and scale of a plane and the degree to which it absorbs or reflects light and sound


Articulation of edges and corners

Since the articulation of a form depends to a great degree on how its surfaces meet each other at corners, how these edge conditions are resolved is critical to the definition and clarity of a form.

1. Contrasting the surface qualities of the adjoining parts.
2. Introducing a seperate and distinct element that is independent of surfaces it joins. articulations of the corner as a linear condition.
3. The opening diminished the corner condition, weakens the definition of the volume within the form and empasizes the planar qualities of the neighboring surfaces
4. Void, neither plane is extended to define the corner, a volume of spaces is created to replace the corner
5. Rouding off the corner empasizes the continuity of the bounding surfaces of a form, the compactiness of its volume and softness of its contour.


Independently of the geographical location, spatial articulations creates identity to architecture. This also applies to the Islamic and moroccan architectre, both traditional and contemporary.


Traditional islamic and contemporary moroccan architecture


Being inspired by nature, we could develop structures that would be as resistant to extreme environmental conditions (especially strong winds and hurricanes which occur on Sahara desert) as Coralline algae is resisant to waves. Additionaly that would let to keep elements of traditional architectural approach.

By creating structures which are articulated, constructed out of smaller elements maybe it is possible to build on unstable grounds, such as deserts. Among others that could be a solution for migrating sand dunes problem which is present on Sahara desert.



The most importans task is to design suitable system of joints that will work in the particular circumstances and will ensure protection from environmental conditions (strong winds, unstable terrain etc.)


There are three main types of articulated structures.

1D – long structural elements + small connecting joints12.jpg

2D – plain elements connected to each other along the edges13.jpg

3D – solids that are structural components of a bigger object14.jpg

Depending on the type of a structure there may be different fabrication methods or combination of them, for example:

– 3d printing, especially for the elastic, flexible joints
– Cast moulding, for the hard structural elements (clay or ceramic)
– Laser cutting



performative ornament

Plane Joint Movement

Understanding Islamic Architecture, Attilo Petruccioli,Khalil K. Pirani


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