Folded plate structures is a type of shell structure consisting of a series of thin plates requiring more material than any other type of shell structure also known as the hipped plate.
Folding plates are used to cover large column-free areas with plate members joined together interminably on the diaphragm with their normal edges supported.
Ease of forming flat surfaces is a distinguishing feature of bent plates, so bent plates are more suited to small areas than bent surfaces that require multiple uses of forms of maximum economy.
Types of folded plate structures:
This folding plates are commonly used for short spans, it does not provide enough area for concrete, the top and bottom to resist compressive stresses.
Butterfly-shaped folding plates:
They are common, used to cover factory roof and petrol pump roof, it also makes provisions for windows.
Trough shaped type folding plates:
They are used for a long time and provide sufficient area for concrete at the top as well as to resist compressive stresses at the bottom.
Tapered folded plate structures:
They are used for aesthetic purposes, Z-shaped folding plates are used exclusively for factory construction as it provides a north-light roof.
Hyped folding plates:
They are used exclusively for tent-shed roofs and cooling towers in thermal power stations.
Two types of reinforcement have been provided in the case of folded plate structures i.e. transverse reinforcement & longitudinal reinforcement.
With cross-sections of folding plates, transverse reinforcement should be provided so that transverse moment can be resisted.
In individual slabs, the longitudinal reinforcement should be able to withstand longitudinal stresses in tension.
Expansion joints should not be provided for large span but must be provided in ridge slabs.
Advantages of folded plate structures:
- A very light form of construction upto span 30 m shell thickness required is 60 mm only.
- The use of concrete reduces both materials and construction cost.
- Longer span can be provided.
- Flat shapes by choosing certain arched shapes.
- It provides better esthetical as compare to other forms of construction.
Disadvantages of folded plate structures:
- Shuttering is difficult.
- Formwork requires more precision.
- Good labour and supervision are necessary.