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Gayathri Rajendran

on 28 February 2014

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GAYATHRI MR, ROLL No. 19, S8, B.Arch
The area between columns of a solid slab has limited structural effect beyond adding weight.

Replacing this area with a grid of
“voids” sandwiched between layers of reinforcing welded wire steel
and an internal lattice girder yields a slab typically 35% lighter that performs like solid reinforced concrete.

Once concrete is poured over the balls in the panels, the Bubble Deck system effectively becomes, and behaves like, a monolithic two-way slab that distributes force uniformly and continuously.


main difference between a solid slab and a bubble deck slab
refers to
shear resistance
In general, Shear resistance will be reduced due to reduced concrete volume.

Shear resistance is proportional to the amount of concrete, as the special geometry shaped by the ellipsoidal voids

In practice, the reduced shear resistance will not lead to problems, as balls are simply left out where the shear is high, at columns and walls

As a BubbleDeck slab acts like a solid slab, the
fire resistance is the matter of the amount of concrete layer
The fire resistance is dependent on the temperature in the rebars and hence the transport of heat.
As the top and bottom of the BubbleDeck slab is solid, and the rebars are placed in the solid part, the fire resistance can be designed according to demands.

A construction method by
eliminating concrete from the neutral axis of a floor slab

that is structurally not performing, as a result dramatically reducing in Dead Weight.

Void formers inside the flat slab
eliminates at least 30% of a slab’s dead weight.

Incorporation of
recycled plastic bubbles as void formers
allows wider space between columns.

Combination of this with a flat slab construction approach spanning in two directions -
the slab is connected directly to in situ concrete columns without any beams
- produces a wide range of cost and construction benefits.

1. Precast Half Slab

Cast In-Situ

Reinforcement Modules comprising pre-fabricated ‘bubble-reinforcement’ sandwich elements.

The modules are placed on traditional site formwork, loose joint, shear & edge reinforcement added and then concreted in 2 stages to the full slab depth.

Suitable for suspended ground floor slab and alteration / refurbishment projects, particularly where site access is extremely restricted.

Can be manually lifted into position
Fixing of the ellipsoids can be made in numerous ways, but
using the reinforcement meshes reduces superfluous material consumption
and allows for an optimal geometrical proportion between concrete, reinforcement and voids.

Voids are positioned in the middle of the cross section
, where concrete has limited effect, while maintaining solid sections in top and bottom where high stresses can exist.


Finished panels, complete precast slab elements. These can be used for limited areas such as balconies or staircases.

Functional applicability:
Residential living, offices
Utility and industrial buildings
Used in offices
Apartments, villas etc.
Laboratories and factories.

As a consequence of the reduced load, it is possible to achieve larger spans than a solid slab.
Cantilevers can be made 10 times the deck height.


The overall floor area can be
divided down into a series of planned individual elements
, up to 3 m wide dependent upon site access

elements comprise the top and bottom reinforcement mesh
, sized to suit the specific project, j
oined together with vertical lattice girders
with the void formers trapped between the top and bottom mesh reinforcement to fix their optimum position.

This is termed a
sandwich, which is then cast into bottom layer of 60 mm pre-cast concrete, encasing the bottom mesh reinforcement, to provide permanent formwork within part of the overall finished slab depth.

On site the individual elements are then ‘stitched’ together with loose reinforcement simply laid centrally across the joints between elements.

The splice bars are inserted loose above the pre-cast concrete layer between the bubbles, and purpose made mesh sheets tied across the top reinforcement mesh to join the elements together.

After the site finishing, concrete is poured and cured. This technique provides structural continuity across the entire floor slab – the joints between elements are then redundant without any structural effect – to create a seamless biaxial floor slab.
Every 5,000 m2 of BubbleDeck floor slab can save:-
1,000 m3 site concrete.
166 ready mix lorry trips.
1,798 Tonnes of foundation loads – or 19 less piles.
1,745 GJ energy used in concrete production & haulage.
278 Tonnes of CO2 – green house gases – emissions

Design freedom
– flexible layout easily adapts to irregular & curved plan layouts.
Reduced dead weight
-35% removed allowing smaller foundation sizes.
Longer spans between columns
– up to 50% further than traditional structures.
Down stand beams eliminated
– quicker and cheaper erection of walls and services.
Load bearing walls eliminated
– facilitating MMC with lightweight building envelopes.

Reduced concrete usage –
1 kg recycled plastic replaces 100 kg of concrete.
Environmentally green and sustainable –
reduced energy & carbon emissions.

8% of global CO2 emissions are due to cement production.

1 tonne of cement.
Releases 1 tonne of CO2
Consumes 5 million BTU of energy
Uses 2 tonnes of raw materials

BubbleDeck Report from A+U Research Institute /Professor Kleinmann - the Eindhoven University of Technology / the Netherlands, 1999

BubbleDeck Report from Technical University of Denmark, 2003




What is Bubble Deck?
Once the steel lattice/void “sandwich” is concreted, it is then precast into panels of various sizes and craned into position on shoring.
The elements placed on temporary propping, loose joint, shear & edge reinforcement added, perimeter and tolerance joints shuttered and then the remaining slab concreted.

Most commonly specified being suitable for the majority of new-build projects.

Requires fixed or mobile crane to lift into position due to the weight of manufactured elements as delivered to site.

The geometry - ellipsoids of a certain size, placed in a precise modular grid.
How to implement?
Between 2002 and 2008 full building regulation approval was issued to 12 UK and Channel Islands projects that have been completed, including
Salisbury Law Courts and 96 apartments
in Le Coie Social rented flats together containing
over 10,000 sq ft (930 m2) of BubbleDeck floors.

In 2007 one floor of two UK projects were partially completed due to reticence of one building control body following which another building control firm was prepared to approve.
High weight to strength ratio
Difficulty in structural health monitoring
Thickness of slab
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