Form work for Curved beams

Curved beams :

Prologue :

The centering and shuttering of the curved beams does provide a different challenge as compared to the normal beams. This article attempts to identify the key steps in undertaking the curved beam form work with prefection.

Types of curved beams :
There could be two types of curved beams :
1. Curved in plan :
This could be either a circular beam or a arc beam either for the water tank or for the roof of a building.
2.Curved in elevation:
Mostly for the ornamental window lintels which are arch shaped beams.
3.Composite ( curved in Plan and elevation both ): Very typical folded structure which is circular in plan and also undulating in level on the circumference.

CURVED /SLANTED FORM WORK

Synopsis :

During an early article on Form work , we have already seen the basic difference between centering-Shuttering and Scaffolding. Please Refer to this link ( Focused form work ) for a quick reference.

We also referred to another article on Form work ( Difference between C ,S & S ).

You would notice that all these discussions were based on the assumption that the RCC surface was either Horizontal or Vertical.

Therefore , it becomes a case of specific interest to all of us , in case we have different surfaces of RCC elements which might include say :

1. Curved in Plan
2. Curved in Elevation
3. Composite surfaces which are curved both in horizontal/vertical planes.

With this article, we now intend to discuss these various other types of surfaces where the form work is something special , different than only Vertical or only Horizontal.

Instead of just doing a theoretical discussion , let us actually see the different cases and discuss the typical features.

This is a slanting type of plinth protection done in RCC slab. The sub-grade has been properly compacted with hard murrum .The necessary slope has been obtained in the sub-grade itself . There is no other form work needed here except that there is a front vertical side and lateral sides which are done in wooden planks.

This is also a simple case since the slab is slanting. The beams and slabs on this floor are inclined and thus we have what is known as a pitched roof. This is done in normal steel plates ( size 3′ x 2′ ). Only difference from normal slab is that the height of the supports ( In this case , the wooden ballies ) have to be of varying lengths so as to match with the sloping profile.

This is a double sloping RCC slab . The slab has been cast with ply wood ( 12 mm thick ,waterproof marine ply , 34 Kg/Sqm. weight ). The only difficulty is in the adjusting the heights of the ballies in the second staging whch is of varying heights.

You can see the curved roof beam . Actually , on this RCC beam , there is no slab as such. This beam has been provided for structural bracing and also serves as a elevation feature. The beam bottom has been completed in wooden planks . Beam sides have been completed using the Plywood sides.

The Bracing beam discussed in the previous pic can be seen in a long shot.

This is a relatively small opening provided in the RCC slab. he opening is perfect circle in shape and has got a peripheral beam . This beam has been completed in Ply wood .

This RCC wall has got a curvature . The internal and external form work has been completed in marine ply . Each lift is 1200 mm ( 4 ‘ in height ). main issue in such shuttering is that both surfaces need to be properly clamped. here this was done with the help of the Tie nuts.

This slab , although is circular in plan , this is horizontal. Therefore , fixing the centering plates was quite easy. On the peripheral portions , wooden planks have been used to match the curved portions . The reinforcement is also quite simple ( both ways ).

Here you can see the Chajja around a circular hall . This Chajja has been completed totally in ply wood . Since the Chajjah is horizontal , the supports in wooden ballies were quite easy to erect.