Biomimetics: Pressurised Structures – Cacti

(C) Andres Harris

A cactus (plural: cacti, cactuses, or cactus) is a member of the plant family Cactaceae, within the order Caryophyllales and is a succulent system that contains pressurised water that gives the organism structural stability as well as being a fundamental life source.

Being a water-container, means that there is no need for other rigid structure such as bark to give structural performance against external loads. Water is an element already in compression and similar structural strategies have been derived from this natural phenomenon in man-made hydraulic structures. Just like Cacti, other living organisms such as Jellyfish, slugs, worms and other plants (crassulas) contain a large percent of water which replaces the need of rigid hard tissues such as bones and barks to achieve structural performance allowing high flexibility.

(C) Omid Kamvari - Andres Harris

In an intermediary scale, the cactus presents a series

(C) Andres Harrisof tubercles which are distributed along the entire body in a spiralling Fibonacci sequence. These tubercles contain water within them and help to cool down the overal surface of the plant as they casts shadow over their neighbouring tubercles, which are partially shaded themselves due to their morphology.

(C) Andres Harris(C) Andres Harris

Each Tuberble has a set of spines (Areoles) that also contribute with shading as well as moisture-capturing from the air.  The morphology of the cactus, with its tubercles also provides aerodynamic performance, in which the air flow generates a “Cushion of Air” around the plant helping with wind deflection, stability and moisture loss due to extreme heating.

(C) Omid Kamvari - Andres Harris

In a micro-scale Cacti store water within their cells (98% water) in a micro-scale.  Each cell can controll the water pressure affecting its neighboiring cells.

(C) Omid Kamvari(C) Andres Harris
Cactus- Skin Canopy

 

Deriving morphological properties of the cactus surface which regulates the overall surface temperature, its aerodynamic properties which allows stability against wind gusts and differentiation given by the water pressure it is possible to design a canopy or surface that takes into account all these performance properties.

 

Mimicking the cactus tubercles I designed a fabric and metal component with an adjustable system that stretches the fabric allowing different depths and giving structural stability, just as water pressure does to cacti systems. the morphology of the component also resembles the cactus tubercles allowing a high degree of shading to the surface itself, regulating the local and overall temperature both of the component, and sub-sequentially the surface.

 

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Overall stability is given by the interaction of each component as a whole system, forming a skin or surface that has structural stability and temperature regulation, as part the surface remains shaded whilst other areas receive a direct impact from the sun.

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