Folded Plates

Folded plates_ Principle Construction consisting of thin , flat elements of concrete, steel, timber, etc.,which are connected rigidly at angles with each other forming a cross section which is capable of carrying a load over a long span. Folded plates are assemblies of flat plates rigidly connected together along their edges in such a way so as to make the structural system capable of carrying loads without the need for additional supporting beams along mutual edges. The distinguishing feature of the folded plate is the ease in forming plane surfaces. Therefore, they are more adaptable to smaller areas than curved surfaces which require multiple use of forms for maximum economy A folded plate may be formed for about the same cost as a horizontal slab and has much less steel and concrete for the same spans. Inclined Plate

Edge Plates –to stiffen wide plates

Folded plates_ Types Longitudinal /Prismatic folding:

Spot / facet folding:

Longitudinal folding is characterized through uninterrupted and linked folding edges where parallel and skew up folds and down folds alternate.

Spot or facet folding requires that several folds intersect like a bunch in one single spot. This results in pyramidal folds with crystalline or facet-like planes.

Single-layered longitudinal folding corresponds in their load bearing structure to a linear load bearing system. Double-layered folding with different directions of their folds can create the structural condition of the plate.

Facet folding can either be based on a triangular shape or on a quadrangular shape. A single or double-layered facet folding resembles the load bearing structure of a plate and can be compared to space frameworks.

Folded plates consist of straight pieces joined with sharp edges. It cannot be made as thin as a shell due to the fact that it is subjected to bending.

Folded plates_ Types

WALLS CONTINUOUS WITH SHELL

TAPERED FOLDED PLATES

EDGE SUPPORTED FOLDED PLATES

FOLDED PLATE TRUSS

CANOPIES

FOLDED PLATE RIGID FRAME

Advantages: Concrete roofs provide inherent resistance to fire, deterioration and to atmospheric corrosion Allow large spans to be achieved in structural concrete which allows flexibility of planning and mobility beneath ground condition require expensive piled foundation. the no. of supporting column reduces so economic advantage it is thicker than shells therefore easier to cast. Disadvantages: Aesthetics of folding plate not that pleasing compared to that of a shell Usually more expensive than roofs lighter in weight comprising roof sheeting

Folded plates_ Virum Sports Hall Architect_Finn Monies & Jørgen Nielsen Location_Copenhagen, Denmark Material_Reinforced Cement Concrete

Plan Virum Sports Hall

Cross Section Virum Sports Hall

Folded plates_ structural analysis

A flat slab construction was not possible due to large span without adding columns between the space or the slab would buckle.

Hence folded plate. The structure has folds in two ways.

Virum Sports hall, facing the railway tracks

Movement

Lightness Less Construction Material

Folded plates_ structural analysis

Exterior: At four corners, to withstand diagonal bending moments tension cables are provided which anchor to the underground. Vertical loads are distributed uniformly along symmetry line

Interior: 6 columns under the furrows that take the focus, leaving the Diagonally there are bending moments at the corners

impression that the lantern is pushing down, producing compression load.

Delft Aula Congress Center Delft,Netherlands

Design Van den Broek and Bakema J.H. van den Broek, JMA de Groot, G. Lance, HBJ Lops

Folded plates_ delft polytechnic school The roof does not simply cover a large open area, but rather a wide variety of spaces requiring very different support systems.

Requirements: Design was the outcome of the need to meet two conflicting but essential requirements: The building, located at one end of the main thoroughfare on the Delft PS campus, had to be highly visible from the road. The building should not obstruct traffic.

Solution: The solution to this paradox was to build an auditorium on the first storey while leaving the ground storey underneath both visually and physically open for access to the main thoroughfare. The raised floor of the auditorium rests on two very wide (polygonal section) columns that are set back from the building perimeter to balance loads

Folded plates_ delft polytechnic school Area of cantilever auditorium: 1600 m2\ Floor slab cantilever:14m (2 columns) Roof supports: 32m (service shaft) no columns at any intermediate point in the auditorium, the roof must be built to project outward from the centre of the building.

Hence folded plate system was employed

CANTILEVER FLOOR SLAB

Folded plates_ delft polytechnic school The enormous depth of 6 m generated is only necessary at the spring line, (axis 13 on the longitudinal section of the building) Unnecessary material is "eliminated" from the roof to form a grid that follows the lines of fold geometry. This lattice-type structure also simplified the installation of skylights.

Girders

Spring line

The rear (tensile) support for this grid consists in a huge girder at section number 18, in turn resting on four columns subjected to tensile forces.

Girders

The basic shape of the roof cross-section is a series of six equilateral triangles.

Folded plates_ delft polytechnic school The cantilever folded roof element, designed as it was to be as lightweight as possible. It does not in fact comprise a continuous shell, but rather a series of cantilevered beams

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Longitudinally, they tend to converge at a point on the free edge. As a result, the inter-beam space steadily increases towards the outer edge,lightening the overall weight of the structure.

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At section 10, the longitudinal profile tilts abruptly downward. Stiffeners at the edge to prevent the lateral opening up of the last fold which follows the trapezoidal shape of the plan.

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