Keeping Sharks and Rocks Away: A few of the countless applications of nets

 

 

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Some of Frei Otto’s sketches from the Institute for Lightweight Structure’s “Netze in Natur und Technik” (1975)

 

Nets have been a perennial source of fascination in fields as diverse as engineering, architecture, art, and mathematics. As such, thinkers in these fields have come up with a dazzling array of applications and uses for nets, which force us to expand upon our preconceptions of what nets are and what they can be used for.

Pause for a moment – how many applications of nets can you think of? The late Frei Otto had a well-known interest in nets and their applications to structural engineering. A flip through a 1975 publication from the University of Stuttgart’s Institute of Lightweight Structures (of which Frei Otto was a director) reveals pages of sketches (see above and below) on net elements, forms, typologies, and applications. The applications range from the prosaic (tennis racquet, hammock) to the extraordinary (stadium roofs, bridges), to the bizarre (airplane barrier, anti-U-boat net).

Personally, my research concerns underwater cable nets, and I’m currently assisting with the design of a net with a very unique application: preventing shark attacks.

La Reunion, a French island in the southern Indian Ocean, is renowned for its surfing and beautiful beaches. However, this paradise has been suffering from a surge in shark attacks in recent years. Since 2011, there have been nineteen attacks, of which seven were fatal. The attacks peaked in 2013, which forced authorities to temporarily ban aquatic activities. As a result, the island’s economy has been strained, with beach-front businesses bearing the heaviest losses.

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“Net Out Of Order,” reads a sign on the empty Boucan Canot beach.

Continue reading “Keeping Sharks and Rocks Away: A few of the countless applications of nets”

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Grow strong and live beautifully: Colombian bamboo structures

While the new group of senior students are getting up to speed with their senior theses, we look back in this weeks blog post on the work of Russell and Lu Lu in Colombia.

In March 2016 Russell Archer (’16) and Lu Lu (‘16) traveled to the city of Cali, Colombia and the coffee region (Spanish: Eje Cafetero) north of Cali where they visited a variety of structures made of south American bamboo species Guadua angustifolia, known as the “vegetable steel” for its impressive strength. These structures range from traditional vernacular houses, roofs and bridges designed by Simón Vélez, to classrooms designed by Andres Bappler. Russell and Lu were inspired by both the abundance and the level of sophistication found in these bamboo buildings.

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Left Image: Russell (right) and Lu (left) standing in front of a huge bamboo forest near a school building construction site at UTP campus in Pereira, Colombia. Right Image: A vernacular bamboo chair in a local bar.

Visiting Cali, Colombia and the surrounding regions showed us how bamboo is deeply ingrained as a part of daily life in Colombia, from chairs and fences to larger scale bridges and buildings. Much of bamboo design is driven by designer’s and builder’s knowledge of the material properties. This knowledge has expanded over generations and has added to the scale of the structures that can now be achieved. At the Universidad Technolόgica de Pereira (UTP), an arch bridge designed by Simón Vélez (http://www.simonvelez.net/) traverses a roadway connecting two parts of the campus. He also designed the CARDER regional office. These bamboo structures are representative of emerging efforts to locally enhance the perception of bamboo as a building material. The efficient joinery techniques that incorporate mortar inserted into the poles and steel bolts, are indicative of the sophistication involved in the bamboo design.

3 View looking across the bridge deck at the Universidad Technolόgica de Pereira by Simón Vélez. The bamboo poles are covered with dark coating that protect them from sun and rain.

4 Russell (left) discussing the structural system of the arch bridge with DAGMA architect Daniel (right)

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Interior Corporaciόn Autόnoma Regional de Risaralda(CARDER) where inclined bamboo poles support the roof Exterior of Corporaciόn Autόnoma Regional de Risaralda (CARDER) with structural timber and bamboo poles

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The refreshing tandem: the works of the engineer Laurent Ney perceived by the visual artist Toshio Shibata

What happens when an artist photographs the works of a master designer and builder? The recently published book Toshio SHIBATA / Laurent NEY shows how the photographer Shibata sees the work of Ney, not for its engineering logic but for its inherent poetry. In this book Ney generously shares with us his views on bridge design alongside the visual artistic perspective of  Shibata.  A most unexpected and refreshing tandem.  We are grateful for this blog text which is the introduction to  the book, published with author’s permission. The book  further showcases hundred photographs of the work by Laurent Ney taken by the Japanese artist Toshio Shibata and can be purchased through this link.

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From Toshio SHIBATA / Laurent NEY – (August 19, 2016). Publisher: MER. Paper Kunsthalle.

Introduction

The design of a bridge starts with the context, a context that includes more than just the physical context of the site, its natural surroundings and landscape. A context in its broadest sense takes in historical, technological, industrial, economic, ecological and procedural considerations, all of which are subject to material and procedural constraints, which the project’s author must respect or, better still, transcend.

The work itself, the creative act, is the projection of the imagined object into the future context of the site. The insertion of this object will of course change the context of the site, as the object becomes part of the place, it becomes a place in itself, it becomes context.  The context or the landscape finds itself altered by this insertion, its reading is modified. One can ask oneself if this reading has been improved or not by it, but of course there is no definitive answer to this question, it is eminently subjective. This is where an outsider’s view, such as that of artist-photographer Toshio Shibata, can reveal a denser reality that can be read on various levels.

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De Lichtenlijn Footbridge, Knokke, BE ©Toshio Shibata for Laurent Ney, Design©Laurent Ney

There are a number of different things that I hold to be especially important in the design of a bridge:

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What is the Optimal Shape for a (trussed) Arch?

Arch bridges date back to Antiquity. Steel trussed walkable arch (such as the one shown in the picture above) can be attractive because they can be prefabricated and thus speed up construction time on site. The deck can be cambered to either allow vertical clearance below and compensate for deflection under its own weight. However the maximum slope of the walkable arch is set by accessibility slope guidelines and needs to be shallow. Because of this shallowness, the arch is prone to in-plane snap-through buckling. This means that the arch can assume an inverted equilibrium position. Since the bridge is also lightweight, it natural vibration can coincide with the pedestrian-induced vibration as was experienced by the visitors to the Millenium Bridge on the day of its opening. When that happens, resonance occurs which can lead to severe structural damage.

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Illustration of arch snap-through buckling (Left) and resonance (right)

So what happens when we try to optimize the buckling or dynamic behavior of the walkable trussed arch bridge by allowing the nodes of the truss top chord to displace? The resulting truss forms, optimized in 2D (nodes only allowed to move in x,y plane) and 3D (nodes allowed to move in all 3 directions) are given in the table below.

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Mass Imperfections.

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The curved shapes of hand-made figurines are widespread in the Bethlehem’s tourism industry. What is intriguing about all these crafts is the precision of the forms given the basic tools used for their fabrication. An established hierarchy and apprentice curriculum maintains the artisans’ skills to a certain standard. Becoming an olive-wood master carver is, among other skills, being able to reproduce a complex-geometry shaped figurine while only looking at it.

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Olive wood artisan – Credits: AAU ANASTAS

The process of fabrication of olive-wood objects in Bethlehem calls high-tech mass customization into question. Mass imperfections is a project that experiments the potential of artisanal fabrication for the construction of large-scale structures.

The project experiments the ability of craftsmanship of stepping back into the forefront of the fabrication processes. Mass imperfections challenges high tech fabrication processes by monitoring and anticipating imperfections of highly skilled artisans.

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