Normally related to but not exclusive to reinforced
concrete thin shell construction, the folded or pleated plate structure is
essentially a three dimensional geometric assembly of planar elements through
rigid edges. The creased surface's stress lines induce a complex transfer of
loads across the surface portions and linear folds of the pattern. Folds
increase the material distance from the configuration’s rotational centre,
which increases the systems’ capacity to resist angular stresses. While an area
can be pulled in one direction buy a load other interrelated surfaces push or
pull in opposing directions. Originating in paper folding principles, multi-directional
folds act as stiffeners.
Divided into surface or truss systems, both strategies
create thin surface polygonal envelopes that behave similarly to arches or
vaults. Much like the voussoir segments of an arch, loads are transferred
through stress line vectors. As the folds are increased in height or depth
overall spanning capacity is increased as each surface mimics a vertical beam.
Tighter and greater geometric subdivision also increases capacity as the stress
and bending moment of each ridge is reduced. The resulting architectural space can
be planar or follow curved patterns.
Skidmore, Owings &
Merrill (SOM)'s folded surface and truss triangular arch at the US
Airforce Academy Chapel at Elpas Colorado or Herbert Yates’ Plydome folded
cardboard agriculture workers’ shelters typified architectural and engineering
fascination with the pleated structures throughout the 20th century. The
folded plate although not exclusive to modernity became synonymous with innovative
structures and materials.
Building on the explorations in engineered timber and
the folded plate as a structural and geometrical archetype, the iBOIS
laboratory at EPFL (École polytechnique fédérale de Lausanne) is examining and experimenting folded plates’
contemporary potentials. Banking on timbers’ relatively low embodied energy and
weight, plywood surfaces reproduce geometrical patterns of paper folding while
being inflexibly joined together. The Chapel St-Loup a collaborative effort between
Localarchitecture and the iBois laboratory demonstrates the simple
manufacturing principle of fixing numerically cut pieces determined from fold
patterns. The joinery is a mix of traditional lap and dovetail to achieve a
rigid edge joint. The exciting research proposed by this university lab
showcases structural capacity, dynamic space creating qualities and the formal
geometric elements of folded architecture.
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| Chapel St-Loup (construction) and iBois laboratory experiment |
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