void slabs

8/13/2019 void slabs

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GUIDED BY: Prof. V.R.SHAHMrs. DHARA SHAHMrs. AANAL SHAH

PREPARED BY: APURV S. BOKILSD 0210



HISTORY OF HOLLOW CORE SLAB BUBBLE DECK TECHNOLOGY SITE INSTALLATION

COMPOSITION/THEORYTYPES OF BUBBLE DECK/COMPONENTSEXAMPLES

REFERENCES



The first hollow concrete block was designed in 1890 byHarmon S. Palmer in the United States. After 10 years ofexperimenting, Palmer patented the design in 1900.Palmer's blocks were 8 in (20.3 cm) by 10 in (25.4 cm) by30 in (76.2 cm), and they were so heavy they had to belifted into place with a small crane. By 1905, an estimated1,500 companies were manufacturing concrete blocks inthe United States.

These early blocks were usually cast by hand, and theaverage output was about 10 blocks per person per hour.Today, concrete block manufacturing is a highly automatedprocess that can produce up to 2,000 blocks per hour



BUBBLE DECK TECHNOLOGY

Bubble deck slab is the slab in which some amount of theconcrete is replaced by the plastic bubbles or ellipsoidwhich are made by the waste plastic material, whichreduces the self weight of the structure.

Design of this type of the slab is based on the euro andthe British codes.



In the 1990ies, a new system was invented, eliminating

the some of the problems. It is used in Dutch:Germaninvented by JORGEN BREUNING. He locks ellipsoidsbetween the top and bottom reinforcement meshes,thereby creating a natural cell structure, acting like a

solid slab.The slab is created with the same capabilities as a solidslab, but with considerably less weight due to theelimination of excessive concrete.



Russia

Australia

Brazil

North America

Denmark

New Zealand

uk



Saves 30 to 50 % weight compared to a correspondingsolid slab – equal stiffness.20% concrete reduction in other components.The reduced weight of the slab will typical result in achange in design to longer spans and/or reduced deckthickness.It is also seismic friendly as it lowers the total weight of thebuilding.

Reduced concrete usage – 1 kg recycled plastic replaces 100kg of concrete. The company estimates that building costs are reduced by8 to 10 %.



SITE INSTALLATION( Type A- Filigree Elements)

• Temporary Support Propping on parallel beams

• Placing Elements – Semi pre-cast elements mechanicallylifted into position

• Joint Reinforcement – Insert loose bottom splice barsand tie top mesh across joints between elements

• Perimeter shuttering Fix shuttering to bottom pre-castconcrete layer & tie to top mesh reinforcement

• Soffit shuttering – Prop plywood across jointsbetween element bays and between elements & columns



Preparation Seal joints between elements, clean and

moisten bottom pre-cast concrete layer• Concreting – Pour, vibrate and aggregate in-situ concrete

• Temporary works – Remove, typically after 3 – 5 days

according to specific site advice• Finishing – no further work required.



Several methods have been introduced during the lastdecades, but with very limited success, due to majorproblems with shear capacity and fire resistance as well asimpractical execution.

Most attempts have consisted of laying blocks of a lessheavy material like expanded polystyrene between thebottom and top reinforcement.

But the use will always be very limited due to reducedresistances towards shear, local punching and fire.

which is why the use of these systems has never gainedacceptance and they are only used in a limited number ofprojects



In principle, Bubble Deck slabs acts like solid slabs.

Designing is consequently like for solid slabs, justwith less load corresponding to the reducedamount of concrete. Thorough investigationsaccording to Euro codes are made at universities in

Germany, Netherlands and Denmark, concludingthat a Bubble Deck slab acts like as a solid slab.



Only top compressive portion and bottomreinforcing steel of a solid concrete slab contributeto flexure stiffness in bending.Bubble deck removes concrete from the center of

the flexural slab and replaces with hollow HDPEspheres. It is having equal bending stiffness as solidslab.But technical university of Denmark also carried

out test on stiffness of bubble deck slab. theyverified the result and they found out, for samestrength, bubble deck has 87% of bending stiffnessof similar solid slab but only 66% concrete volume

due to HDPE spheres.



In calculations, a reduction factor of 0.6 isused on the shear capacity for all bubbledeck slab.

This guarantees a large safety margin. Areaswith high shear loads need therefore a

special attention, e.g. around columns. Thatis solved by omitting a few balls in thecritical area around the columns, thereforegiving full shear capacity.



The simple Bubble Deck may alsobe delivered to the building site aspre-cast factory-made slabs.( pre cast )



COMPONENTS



-Grade of steel: Generally Fe

500,550.

-Rebar size depends on thethickness of the slab and span.

-spacing: Max 1 m. or maximum3 balls between two girder.Two types:(a). Self supporting(b). Trussed type.



- Main bar 10mm minimum – for 200 to 300 mm slabthickness.

- 12mm- for size ≥ 300 mm



Concrete

Type: self compacting concreteGrade: Any grade of concrete can be used,

generally M 20, 30 grade is use.



The largest Bubble Deckstructure so far erected inGreat Britain. The structurecomprises 7,800 m 2 of BubbleDeck floor slabs between 3and 6 stories high supportedon in-situ reinforced concretecolumns. Over £400,000 ofsavings were realized as adirect result of incorporatingBubble Deck into this project,amounting to a 3% saving offthe total project cost.

1.LeCoieHousing:



Sogn Arena, Oslo in Norway

http://en.wikipedia.org/wiki/File:Kb_bdimage022.jpg






City Hall andOffices, inDenmark






Bubble deck-advanced structure engineering by Paulharding,managing director bubble deck C.I.ltd.

Bubble deck structure solution (UNITED KINGDOM)

Structural Behavior of bubble deck slab byMassachusetts institute of Technology

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