Softer boundaries
One of the virtues of using cables to support membranes is that it
provides a more gentle means of support than using high points.
The number of points supported is increased - and the force
required at each point is reduced.
The effect is similar to that produced by using curved
arches (or bent poles) to push up the fabric - though of
course using cables tends to be lighter and cheaper.
Even softer boundaries
This page addresses the question of whether the membrane
support can be softened further somehow.
One way of doing this is to use the
flat pattern.
Another method employs a thermal insulator around the cables
- which increases their effective radius.
However, there's also something else that can be done:
Most pleated structures use a single valley cable - like so:
One cable
Looking at some of the structures that have been built, the
possibilty of using more than one valley cables arises.
More than one valley cable
Attempting to cover more than a small distance like this is
probably impractical - since the cables would tend to get
pushed together at the bottoms of the valleys - unless they
were held apart somehow.
However the cables being pushed together may not be the end
of the world - even directly adjacent cables can help to
distribute the curvature in the membrane surface over a
larger area.
Two cables
Two cables is the most obvious possibility. Together these
two cables create a more gentle curvature than is produced
by a single cable.
Three cables
Assuming the pleats are not too deep, three cables may also
be possible.
These multi-cable patterns have a price - there are more
cables and fittings - which are likely to increase costs and
assembly time.
However if they help avoid bruising, damaging and wear of the
fabric membrane it might well be worth it.
Links
The essay on blunt pleats is related to this one.
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