Tensile Surface Structures - IFRC-Shelter Research Unitifrc-sru.org/wp-content/uploads/2014/09/Prof-Mollaert... · 2014-09-09 · Tensile Surface Structures Hanging cables + tensioning

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Tension forces in textile architectureIntroduction to form-finding, possible shapes, equilibrium of forces and structural behavior of tensioned surface structures

[email protected]

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Tensile Surface Structures

Technical textiles Coated woven materials

Only resist

to tension

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Form-active structures =

Depends on the external load

Large deformations can occur

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Hanging cables

+ tensioning cables

opposite curvature

=

Stable construction

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Anticlastic surface = Double curvature

Positive in 1st direction + negative in 2nd direction


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Synclastic surface = Double curvature

Positive in 1st direction + positive in 2nd direction

Inflated systems


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Pretension

stabilises the system:

can carry downward loads

F1 F1

F2

F2

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Pretension

stabilises the system:

can carry upward loads

F1 F1

F2

F2

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Pretension

in the surface

stabilises

the shape

Annick Schotte DEGRE2

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Typical anticlastic shapes

Saddle

Conical with high or

low points in the surface

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Formfinding

Geometry

of the equilibrium form

+

Internal forces

in this equilibrium form

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Primary structure

Transfers loads and pretension to the foundations

Can consist of● Struts + tie cables

● Beams

● Arches…

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Consist of

supporting structure

curved tensioned surface

connections

anchorage

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Clever roof?

Disaster relief

Plastic tarp?

Structurally stable set-up?

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Clever roof? Avoid ponding and wrinkling?

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Clever roof concept

New type of shelter!

To be used during the first hours after disaster

Material & components pre-positioned

Shelter for rain, heat and cold

To be used for different functions: first aid, meeting zone …

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Clever roof concept

Structurally stable

Cheap

http://www.unrefugees.org.au

Clever roof

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Clever roof concept

‘Simplistic design with natural materials to meet basic needs …

nothing fancy, nothing complicated, as architecture was just being born as a utility’

http://landarchs.com/tick-vs-tock-architecture/

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Clever roof concept

Existing shelters

Well ‘tensioned’ tent: Sahrawi tent Aousserdrefugee camp 2002http://www.flickr.com/photos/simon-james/2676927132/in/photostream/

http://www.ragdollfoundation.org.uk/wmmhdiaries/saharafilm.html

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Clever roof concept

Designs by architect

Frei Otto

Based on ‘traditional’ tents

IL29

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Clever roof concept


Frei Otto

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Clever roof concept


Frei Otto

Flexible

Modular

Robust

Not made

from flat sheets

IL29

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Clever roof concept

Design by architect Shigeru Ban

PAPER in Architecture

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Clever roof concept

Ban’s practice proposes a return to first principles –exploring the necessity of shelter and its crucial role in the formation and preservation of human society

www.shigerubanarchitects.com

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Clever roof concept

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Clever roof concept

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Clever roof concept

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Clever roof concept

Ban’s experiments in temporary shelter do not only serve craft, but is dedicated to an ease of use that invites the participation by anyone –skilled or unskilled – at any time


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Clever roof concept

‘For me, I believe a structure made with materials light enough to be constructed by just one person serves the purposes better’

Shigeru Ban


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Clever roof concept

A group of students and graduates from the Architectural Association School in London produced a kit that can help turn unused spaces into public amenities

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Clever roof concept

Asif Khan, Omid Kamvariand Pavlos Siderisproduced the Public Space Shading Canopy kit after their successful experience erecting a 15m-long lycra canopy in the slum of Favela do Pilar in Recife, Brazil

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Clever roof concept

The bright yellow awning was slung from telegraph poles and buildings using cables

It was erected in just four hours with the help of locals

It immediately turned the neglected thoroughfare into a vibrant public space

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Clever roof concept

The new kit, whichprovides shelter from sunand rain, contains all the materials and tools people need to createtheir own canopies

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Clever roof concept

It comes in S, M, L and XL sizes

Robustness?

http://archithoughts.wordpress.com/

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Clever roof concept

Elementary shelter:

Water tight

Strong

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Clever roof concept

How to obtain a safeClever roof kit?

http://www.survival-spot.com/survival-blog/the-a-frame-tarp-shelter-simple-lightweight-and-

effective/

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Clever roof concept

A well tensionedmembrane

Compression elements

Ropes or belts

Anchorage

Made from tarps

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Clever roof concept

A kit solution:

different forms with thesame elements

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Clever roof concept

A kit solution:

Combined with other structural sub-systems

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Clever roof prototypes

Cable strut model:

- 4 poles

- 8 ropes

- 2 high, 2 low points in the roof (4mx4m)

L H

H L

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Clever roof

Cable strut model:

- 4 poles

- 8 ropes

- 2 high, 2 low points in the roof

L H

H L

Clever roof? Avoid ponding and wrinkling!

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Cable strut model:

Material strength?

L H

H L

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Bending active model:

using slender curved beams

250 TE Work Tent

€535

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using slender curved beams

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- 2 bended beams

- 5 poles

Appropriate bending stiffness needed!

H H

L H L

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Woven material!

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Clever roof analysis

Hypar: fibers aligned with the edges

High stresses in the boundaries, low in the central part

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Align the weave directions with the directions of highest curvature

// with the edges (6mx4m)

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Uniform upward wind loading 0.6kN/m2:

Deflection > 0.5m

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‘Light’ set-up for light weather conditions

Improve performance when needed: Increase the pre-stress

Add/reinforce poles and tie down ropes

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Reinforce the membrane by additional belts or ropes: Tensioning down for uplift

Increasing stiffness/strength in the hanging direction

Assure anchorage

Change the shape (fold down)

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SLS: Self weight: 2.6 N/m²

Wind pressure: 180.3 N/m²

Deflection without reinforcement: 45cm

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Wind pressure: 180.3 N/m²

Deflection with reinforcement: 26cm

Ponding…

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Uplift wind: 360.6 N/m²

Deflection with reinforcement: 59cm

Provide stiffer ropes or belts

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Clever roof connections

‘God is in the details’

Nic Goldschmidt

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A structure is as strong as the weakest link …

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An appropriate pretension is crucial

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Connections

Low-tech

Cheap

Light

To be assembled by hand building

Robust

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Connections

Polyethylene sheets

PVC-coated polyester sheets

Polyester ropes

Polyester belts

Wooden poles

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Typical connections

- Rope-rope

- Rope-membrane

- Membrane-membrane

- Pole-pole

- Pole-membrane

- Pole-rope

- Rope-anchorage

- …

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Several solutions

Membrane-rope

Robustness?

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Several solutions

Membrane-rope

Robustness?

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Several solutions

Membrane-membrane

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Several solutions

Pole-membrane

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Several solutions

Pole-rope

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Several solutions

Rope-anchorage

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Clever roof


Nic Goldschmidt

http://www.self-sheltering.org

Strength?

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How to introduce the pre-tension?

Easy in use

Strong

Safe

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Optimisation according the use in the kit:

Connections

Poles

Ropes

Materials

Dimensions

Transport …70

Building with textiles

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Building with textiles

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Temporary pneumatic

Modern Tea House

Museum für angewandte Kunst

(MAK), Frankfurt 2007

The inflatable Tea Pavilion

is as a kind of a sculpture

to be used as a temporary room

for ceremonies

Example

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Already on his first drawings

Kengo Kuma showed

a smoothly shaped

double-bowl structure

The design was modified

adjusted

during monthly meetings

of the team

Example

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Example

Membrane

HF weldable Gore Tenara

630 gr/m² PTFE-fabric

coated with fluor foil

with 38% translucency

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Example

The organic shaped structure

with membrane cover

became a self-carrying

double-wall pneu

with minimized assembly

and dismantling times

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Example

At the footprint the 2 covers are air-tightly welded + 3-4 times per m² point-wisely joined with thin synthetic ropes which leads to a golf ball shape when the air is blown in

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The Modern Tea House

was very concisely designed:

form, material

and structural analysis were one

The details were tested

and optimized

Example

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From 10mbar internal pressure

the ‘Peanut’ stands up

and with 15mbar

the flexible bowl

is stable enough to face a storm

Example

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Example

The Modern Tea House

is a thin-skinned

simple room

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Clever roof


Nic Goldschmidt


Clever roof: complex constraints!

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Clever roof


Nic Goldschmidt


Constraints!

Holistic approach!

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Clever roof kit

[email protected]

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Tensile Surface Structures - IFRC-Shelter Research Unitifrc-sru.org/wp-content/uploads/2014/09/Prof-Mollaert... · 2014-09-09 · Tensile Surface Structures Hanging cables + tensioning