Folded Plate Structures-Principle and Structural Behaviour

Folded plates are structures that are obtained by assembling flat plates rigidly along their longitudinal edges such that the final structural system carries loads without the need for additional supports like beams along their mutual edges. Folded plate structures are 3-D structures or special structures that are derived from folded structural element which maintain mutual relationship in space.

What are Folded Plate Structures? Principle and Structural Behaviour

Compared for other shell structures, folded plate structures are easily manufactured with less use of formwork material. But, as it has more bending in alignment, more material is consumed compared to other shell structures.

Principle of Folded Plate Structure

The folded arrangement of the structures are an inspired principle similar to a palm leaf or a sea shell. Their folded arrangement improves the structural stiffness and load carrying capacity. Hence, adjacent folded plates in series can show similar load carrying capacity and structural stability.

Folded Structures Resembling Palm Leaf

When heavy loads are on these plates, to resist the flattening of the folded plates, the ends can be supported using a wall or a beam or a column. The supports are provided along the direction of the span.

Structural Behaviour of Folded Plate Structures

Structural Behaviour Folded Plate Structure

As shown in the figure below, the folded structures are aligned in a uniform zig zag form. The loads that are coming on the structure is transferred to the shorter side of the single element. The resulted axial force is divided between the adjacent elements. This is then transferred to the bearings. Hence, the traverse loads coming on the structure is resisted using plate and slab action.

Traverse Bending in Folded Plates - Slab Action

Here, the load results in traverse bending of the folded plate elements, and bending moment is maximum at the centre of the folded plate slab. The loads that acts normal to each plate results in traverse bending between the junction of the plates. This is called as slab action.The longitudinal bending of the plates in their own plane is called as "Plate Action".

Longitudinal Bending of Plates- Plate Action

Bending in folded plate structures cause the top portion to be in compression and bottom in tension. The folded plates can get flattened under gravity load, which can be prevented using frames or walls. There are chances for end buckling which can be resisted using edge beams.

Typology of Folded Plate Structures

Folded plate structure is classified primarily based on the shape of the final structure. This affects the load transfer mechanism as well as the direction of relying folded structure. Based on this, folded plate structure can be classified into:
  1. Linear Folded Plate Structure
  2. Radial Folded Plate Structure
  3. Spatial Folded Plate Structure

Types of Folded Plate Structures

Analysis of Folded Plates

The basic assumptions while analyzing folded plates are:
  1. The structure is monolithic with rigid joints.
  2. The material is homogeneous, isotropic and elastic.
  3. The length of each plate is more than twice its width.
  4. Plane section before bending remains plain after bending.

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