Flat pattern

Photographs

Cable-stabilised roof

Parallel cables support the structure against both upward and downward perturbations.

They do this by running through cable sheaths - which are glued, welded or stitched to the bottom of the membrane.

Where the cables themselves need stabilising, they pass through holes made in the strips, are anchored, and then pass back through another hole.

Cable-stabilised roof

Cable-stabilised roof

Cable-stabilised roof

Pros and cons

Advantages

• The flat pattern is better at making completely flat sheets of material;

• The membrane is even less likely to require patterning than with pleated designs;

• The flat pattern works better with rigid and semi-rigid materials; materials that do not take kindly to being folded or bent;

• The cables are kept on the inside - this is good because running cables on the outside of a structure exposes them to corrosion - and affects the exterior surface in a manner that might retain water and cause corrosion or thermal damage;

• Forces applied by the cables to the membrane are minimized - which is likely to help prevent wear and tear. By contrast in pleated patterns the valley cables typically do without anchoring - and are stabilised by the membrane - resulting in considerable forces between the membrane and those cables.

• The flat pattern makes no effort to prevent horizontal surfaces forming - whereas pleating usually helps to prevent pooling by tilting surfaces away from the horizontal plane;

• The flat pattern has considerable additional construction costs - primarily due to the cable sleeves that need to be cut, and attached in precisely the correct places;

• Assembly is also more complex - due to the need to pass the cables through the sleeves;

• Use of pleated patterns tends to result in membrane surfaces which have at least some curvature - and this helps stabilise the membrane. By contrast, the flat pattern is flatter and less curved - and is consequently more likely to oscillate and ripple;

• In pleated patterns, tension in the membrane causes slight curves in the cables - which prevents them from oscillating up and down between their anchors. No such effect is present in the flat pattern - there is practically no force transmitted from the membrane to the cables. As a result in the absence of regular stabilisation the cables are more likely to move up and down;

• Tensioning the membrane of pleated structures in at least one dimension can often be done by tightening the valley cables. This is relatively convenient - but is not possible with the flat pattern.

Links

Eden project use of the pattern 1 Eden project use of the pattern 2 Eden project use of the pattern 3