Composite floors

COMPOSITE FLOORS
Ar. Pradeep Kumar Yadav
Assistant Professor
Institute of Architecture & Town Planning
Bundelkhand University, Jhansi

COMPOSITE FLOORS (CONTENTS)
• INTRODUCTION
• CLASSIFICATION
• DOUBLE FLAGSTONE FLOORS
• FILLER JOIST FLOORS
• JACK ARCH FLOORS
• R.C.C. FLOORS
• HOLLOW BLOCK & RIB FLOORS
• PRE-CAST CONCRETE FLOORS
• BIBLIOGRAPHY
COMPOSITE FLOORS By Ar. Pradeep Kumar Yadav, Assistant Professor, IATP, BU, Jhansi

COMPOSITE FLOORS (Introduction)
• The floors composed of more than one material are known as the composite floors.
• They are found to possess the following advantages over timber floors:
1. Resist fire in a better way
2. Can be easily cleaned & hence, they posses better hygienic properties than the timber floors.
3. Can be conveniently adopted for greater spans.

CLASSIFICATION OF COMPOSITE FLOORS
Composite floors are classified into following types:
1. Double Flagstone Floors
2. Filler Joist Floors
3. Jack Arch Floors
4. R.C.C. Floors
5. Hollow Block & Rib Floors
6. Pre-Cast Concrete Floors

Double Flagstone Floors
• The flagstones are used in the two layers.
• If the span is about 4 m, only rolled steel joists are provided.
• If the span exceeds 4m, a framework consisting of rolled steel beams & joists is formed.
• The steel beams are placed at a distance of about 3m centre to centre & the joists are placed at right angles to
the beams.
• The flagstones of about 40 mm thickness & of suitable widths are fixed on the lower flanges & upper flanges.
• The joints of top layer of flagstones are finished in a better way to give a appearance.
• The filling of selected earth or concrete is done in the space b/w the two layers of flagstone.

Filler joist Floors
• The small sections of rolled steel joists are placed in concrete.
• The joists may either rest on wall or on steel beams.
• The joists act as a reinforcement & are spaced at a centre to centre distance of 600 mm to 900 mm.
• The concrete should completely surround the rolled steel joists & beams with a minimum cover of 25 mm over the
filler joists.
Filler joist floor
Connection of R.S. beam with R.S. Joists

Jack arch floors
• In this type of floors, the brick arches or cement concrete arches are constructed.
• These arches rest on the lower flanges of mild steel joists.
• The joist in turn rest either on wall or on beam.
• The joists are placed at a distance of about 800 mm to 1200 mm centre to centre.
• The rise of arch should be 100 mm to 200 mm.
• Minimum depth of concrete at the crown should be 150 mm.
• The disadvantage of this type of floor is that it does not give a plain ceiling surface.
• There are two types of Jack arch floor
1. Brick jack arch floor 2. Cement concrete jack arch floor

Jack arch floors (Construction of Brick Jack arch floor)
• The centering for brick arch is prepared.
• It is usually in the form of a segmental piece of wood of thickness of about 40 mm.
• Its length is equal to the span of arch & its shape corresponds to the soffit of the arch.
• The ends of the centering are slightly cut off at ends.
• The bricks are laid on edge from both the joists.
• The end bricks are cut to fit firmly with the joists.
• The key brick is introduced at the centre of arch.
• The top flooring is provided on a bedding of lime concrete or cement concrete.

Jack arch floors (Construction of Cement concrete Jack arch floor)
• The centering for cement concrete arches is prepared.
• It usually consists of a steel plate of about 3 mm thickness & bent to the shape of the jack arch.
• The steel plate has pair of holes at 750 mm centre to centre all along the length of the plate.
• The plate is supported by means of steel bars with eyes & wooden blocks.
• The concrete is then laid on the centering to the required thickness.
• The centering is removed only when the cement concrete has obtained sufficient strength.
• The surface is kept wet for about 10 days & then, the finishing of top surface & finishing of arch surface are
carried out.
• If the span between the supports exceeds 3.60 m, the rolled steel beams of required section are provided.
• The rolled steel joists rest on rolled steel beam.
• The beams are placed at a centre to centre distance of about 2 to 3 m & concrete or stone bed blocks are
provided at their ends.

Jack Arch Floors ( Construction of Concrete jack arch floor)

R.C.C. Floors
•
• This type of floor is widely used in modern construction.
• The steel bars & concrete are used to form a floor.
• The slab & beam are designed as per loading coming on the floor & proper reinforcement is placed at a suitable place.
• In case of R.C.C. slab, the thickness varies from 80 mm to 150 mm .
• Main reinforcement is generally in the form mild steel bars of diameter varying from 9 mm to 12 mm.

R.C.C. Floors

R.C.C. Floors (Flat slab)
• An important development in R.C.C. floor is that of a flat slab R.C.C. floor.
• It is a typical type of R.C.C. construction in which the slab is built monolithically with the supporting columns without
any provision for beams.
• The flat slab may be with drop or without drop.
• The term drop is used to indicate that part of slab around the column having greater thickness than the rest of the slab.
• The reinforcement in the flat slab can be arranged either in two- way system or four- way system.
• For ordinary loading conditions, the two-way system of reinforcement is generally adopted.
The flat slab construction grants the following advantages:
1. As the slab is constructed without any beam, a flat ceiling is obtained which gives attractive appearance from the
architectural point of view.
2. It is considered less vulnerable in case of fire as compared to the ordinary slab-beam construction.
3. The formwork is simple & economical.
4. Economical for large spans with heavy live loads. It grants better diffusion of light.

R.C.C. floors (Flat slab)

Hollow Block & Rib Floors
• The hollow blocks of concrete are used to reduce the total weight of the floor.
• The blocks are placed 100 mm apart & in this space, the mild steel bars are placed.
• A minimum cover of 80 mm is kept at the top.
• Suitable flooring at top & ceiling finishes are provided.
• The blocks are provided with rough or grooved surface so that they can develop enough bond with the concrete.
• This type of floor is economical, fire proof, sound proof & light in weight.
• If properly designed, this type of floor can even be used to carry heavy loads.

Pre-cast concrete floors
• Pre- cast units are used for floor.
• They may be supported either on walls or on rolled steel joists.
• The sides of each unit contain grooves which are used to connect the adjacent units.
Advantages:
• The construction work can be carried out speedily as there is absence of operations like watering , curing etc.
• The members are light in weight & hence the foundation cost proves to be economical.
• They are fire- proof & sound- proof.
• They do not require formwork during construction.
• They have good thermal insulation.

Disadvantages:
• There are chances for breakages to occur during their transport from factory to the site work.
• They prove to be economical & cheap only when manufactured on a large scale.
• They require careful supervision & skilled labour during their manufacturing process.
• They require fairly uniform spacing of beams & columns throughout the structure which becomes practically difficult.
• They should be properly designed to resist the stresses developed during transportation & handling operations.

BIBLIOGRAPHY
• Floors by Barry’s book “The Construction of Buildings Volume-I”
• Floors & floorings by S.C. Rangwala’s book “Building Construction”.
• https://www.dimensions.guide/element/two-way-concrete-flat-slab-floor-system
• https://in.pinterest.com/pin/339247784417106366/
• https://www.quora.com/Is-it-ok-to-construct-a-building-without-any-type-of-beams
• http://www.sketchup3dconstruction.com/const/how-to-design-slab.html
• https://www.sciencedirect.com/science/article/abs/pii/S0950061812007945

THANK YOU

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