Bubble deck slab
contents
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Abstract
Introduction
Type of bubble decks
Example of projects
Effect
Materials
Why bubble deck slab
Shear
Bending strength
Durability
Deflection
Vibration
Fire resistance
advantages
Experimentation and results
Scope of future use
Conclusions
reference
Abstract
Bubble deck slab is a method of virtually eliminating all
concrete from the middle of a floor slab, which is not
performing any structural function, thereby dramatically
reducing structural dead weight.
• High density polyethylene hollow spheres replace the ineffective concrete in the centre of the slab, thus decreasing the
dead weight and increasing the efficiency of the floor.
• By introducing the gaps leads to a 30 to 50% lighter slab which
reduces the loads on the columns, walls and foundations, and of
course of the entire building.
• The advantages are less energy consumption - both in
production, transport and carrying out, less emission - exhaust
gases from production and transport, especially Co2.
INTRODUCTION
• BUBBLE deck slab is a biaxial hollow core slab invented in
Denmark. It is a method of virtually eliminating all concrete from
the middle of a floor slab not performing any structural function
thereby dramatically reducing structural dead weight.
• Bubble deck slab is based on a new patented technique which
involves the direct way of linking air and steel.
• Void forms in the middle of a flat slab by means of plastic spheres
eliminate 30%-50%of a slab's self-weight removing constraints of
high dead loads and short spans Its flexible layout easily adapts to
irregular and curved plan configurations.
• The system allows for the realization of longer spans, more rapid
and less expensive erection, as well as the elimination of down-stand
beams.
• The Bubble deck slab floor system can be used for storey floors,
roof floors and ground floor slabs.
• Since the weight of the structure reduced, this type of
structure can useful to reduce earthquake damage.
• Bubble deck slab is composed of three main materials
they are steel, plastic spheres and concrete.
• 1) Concrete :The concrete is made of standard Portland
cement with max aggregate size of 20mm.No
plasticizers are necessary for concrete mixture.
• 2) Steel :The steel reinforcement is of grade Fy60
strength or higher. The steel is fabricated in two forms meshed layers for lateral support and diagonal girders
for vertical support of the bubbles.
• 3) Plastic spheres :The hollow spheres are made from
recycled high-density polyethylene or HDPE.
Types of Bubble Deck
Type A- Filigree Elements
Type B- Reinforcement Modules
Type C- Finished Planks
Type A:- Filigree Elements
Type-A is a combination of constructed and unconstructed elements. A 60 mm thick
concrete layer that acts as both the formwork and part of the finished depth is precast
and brought on site with the bubbles and steel reinforcement unattached.
The bubbles are then supported by temporary stands on top of the precast layer and
held in place by a honeycomb of interconnected steel mesh.
Additional steel may be inserted according to the reinforcement requirements of the
design. The full depth of the slab is reached by common concreting techniques and
finished as necessary.
Type B:-Reinforcement Modules
• A reinforcement module one which consists of a pre-assembled
sandwich of steel mesh and plastic bubbles, or "bubble lattice“.
• These components are brought to the site, laid on traditional
formwork, connected with any additional reinforcement, and then
concreted in place by traditional methods.
Type C:- Finished Planks
• Is a shop-fabricated module that includes the plastic spheres,
reinforcement mesh and concrete in its finished form.
• The module is manufactured to the final depth in the form of a plank
and is delivered on site.
• Requires the use of support beams or load bearing walls. This class
of Bubble Deck is best for shorter spans and limited construction
schedules.
Examples of Project
Millenium Tower Rotterdam
• The first high rise building erected with Bubble Deck filigree elements and
the second highest building in Netherlands, 34 stories and 131 meter high.
• Bubble Deck was chosen, in spite of being a completely new product,
because of its advantages in cost , construction time and flexibility and
because of environmental issues. Beams could be excluded resulting in two
more stories than planned in the beginning for the same building height.
Built in 1998-2000.
•
Effect
The basic effect of the bubbles is the weight reduction of the deck. The dead load of the
Bubble Deck is 1/3 lesser than a solid deck with the same thickness – and that without
effecting the bending strength and the deflection behavior of the deck.
MATERIALS
STEEL
–The
steel
reinforcement is of MS or
HYSD can be used.
PLASTIC
SPHERES
•hollow spheres made
from recycled high density
polyethylene.
• Enough strength &
rigidity.
• Not porous.
• Doesn’t react
chemically with
concrete or steel.
CONCRETE-the concrete is made of
standard Portland
aggregate size of
¾ inch.
cement
with
max
WHY BUBBLE DECK SLAB ?
No compromise for strength&
serviceability
Flat slab technology
(no need of beams )
Longer spans
Pre fabricated
&
cast in-situ
Shear
• The main difference between a solid slab and a voided biaxial slab refers to
shear resistance. Due to the reduced concrete volume, the shear resistance
will also be reduced.
• Near the columns, bubbles are left out so in these zones a Bubble deck slab
is designed exactly the same way as a solid slab. Shear resistance of Bubble
deck slab is 0.6 times the shear resistance of a solid slab of the same
thickness .
• 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.
Bending strength
• Bubble Deck when compared to a solid deck, both
practically and theoretically.
• The results in the table below shows that for the
same deck thickness, the bending strength is same
for Bubble Deck and for a solid deck and that the
stiffness of the Bubble Deck is slightly lower.
• Bending stresses in the Bubble Deck slab are
found to be 6.43% lesser than that of solid slab.
• The ultimate load value obtaining bending tests were
upto 90% greater than the ultimate load value. The
bottom reinforcement steel and the top compressive
portion of stress block contributes to flexural stiffness
in the bending.
Durability
• The durability of bubble deck slab is not fundamentally different
from ordinary solid slabs.
• Bubble deck slab joints have a chamfer on the inside to ensure that
concrete surrounds each bar and does not allow a direct route to air
from the rebar surface. This is primarily a function of the fire
resistance but is also relevant to durability.
• Cracking in Bubble deck slab is not worse, and probably better, than
solid slabs designed to work at the same stress levels.
• Bubble deck slab possesses a continuous mesh, top and bottom,
throughout the slab and this ensures shrinkage restraint is well
provided for and that cracking is kept to a minimum .
Deflection
• Deflection of Bubble Deck is 5.88% more than
solid slab as the stiffness is reduced due to the
hollow portion.
• Strengthened Bubble Deck has low deflection
compare to un strengthened Bubble Deck slab.
• Conventional slab carried the stress of about
30.98 MPa by applying the udl load of about 340
kN and causes deflection of 12.822 mm.
• The Bubble Deck slab carried the stress of about
30.8 MPa by applying the udl load of about 320
kN and causes deflection of 14.303mm.
• The Bubble Deck slab can withstand 80% of
stress when compared with conventional slab.
• Slide variation occurs in the deformation when
compared to conventional slab.
Vibration
• RC slab structures are generally less susceptible to vibration
problems compared to steel framed and light weight skeletal
Structures, especially using thin slabs.
• However, Bubble deck slab is light and is not immune from
vibration in all cases so this must be checked just as it should be in
appropriate solid slab applications.
• The most effective weapons against vibration particularly resonant
vibration, are stiffness and damping.
• If we consider damping to be similar to solid slabs, and concentrate
on stiffness, we may observe that a Bubble deck slab can provided
over 2 times the stiffness obtained from a solid slab for the same
quantity of concrete used.
Fire resistance
• The fire resistance of the slab is a complex matter but is
chiefly dependent on the ability of the steel to retain sufficient
strength during a fire when it will be heated and lose
significant strength as the temperature rises.
• The temperature of the steel is controlled by the fire and the
insulation of the steel from the fire.
• In an intense, prolonged fire, the ball would melt and
eventually char without significant or detectable effect
• Fire resistance depends on concrete cover nearly 60-180
minutes.
• Smoke Resistance is about 1.5 times the fire resistance.
• Balls simply carbonize. No toxic gasses will be released.
Advantages
•
•
•
•
•
•
•
•
•
Structural
Less weight.
Increased strength.
No need of beams.
Only few columns required.
Larger span.
Free choice of Shape.
Less foundation depth.
Less excavation required.
15 M
• Construction
• Light in weight less equipment is required.
• Easy incorporation of ducts and pipes into slab.
• Less work on construction site.
• Engineering
• The biaxial flat slab system and columns are ideal for
structures with high resistance against Explosions.
• These slabs and column system acts as an elastic
membrane which transfer horizontal forces to stiff
vertical structures which is used for Earthquake
resistant designs.
•
•
•
•
•
•
•
•
•
•
Environment
Less material and energy consumption.
Reducing Co2 emission up to 40 kg/m2.
1kg of plastic replaces 100kg of concrete.
Every component can be recycled.
Economy
Savings in materials.
Transportation costs reduced.
Faster construction time.
Buildings can be more flexible and easy in installations.
Experimental studies
1.Shear strength- 80% of solid deck slab
2.Deflections 5% more as solid deck
3.Weight
40% less than a solid slab
4.Fire resistance - 65% of solid slab
Scope of future use
• Used for constructing all types of building
especially sky scrapers.
• Best for larger span halls like theatres and
auditoriums.
• Pedestrian bridge decks.
• Used in parking areas as less number of
columns are required.
Conclusion
• Weight reduction is 50% compared to solid.
• The bubble deck technology is environmentally green
and sustainable; avoiding the cement production allows
reducing global Co2 emissions.
• In comparative of conventional slab the volume of
concrete in bubble deck (continuous) are less required,
that is 25% approximate.
• Cost and time saving by using bubbles in the slab like
weight of slab, concrete volume indirectly load on the
beam and walls also decrease/ less so that building
foundations can be designed for smaller dead loads.
REFERENCES
• [I] Tina Lai "Structural behavior of bubble deck slab and their
applications to lightweight bridge decks" ,M.Tech thesis, MIT, 2009.
• Arati Shetkarand & Nagesh Hanche an Experimental Study On
bubble deck slab system with elliptical balls, NCRIET-2015
&Indian J.Sci.Res. 12(1):021-027, 2015
• [3] Martina Schnellenbach-Held and Karsten Pfeffer,"Punching
behavior of biaxial hollow slabs" Cement and Concrete Composites,
Volume 24, Issue 6, Pages 551-556, December 2002
• [4] Sergiu Calin, Roxana Glntu and Gabriela Dascalu, "Summary of
tests and studies done abroad on the Bubble deck slab system", The
Buletinul Institutului Politehnic din LV (LIX), f. 3, 2009
THANK YOU
For your attention