DETAILS OF ONE WAY SLAB REINFORCEMENT

Reinforcement detailing of a slab is performed on the basis of its support conditions. Support to slab is generally provided through walls or beams or columns.

A slab is called one way if the supported is provided from two opposite edges. So, the prime load is transmitted onward the spanning direction. Here, the proportion of longer extent to shorter extent is over 2. In one way slab, one side is greater than the other one. In one way slab, the bending occurs mainly in one direction only (spanning direction).

Consequently, the main reinforcement is necessary to withstand the moments produced and designed for the same. The main reinforcement is arranged at the bottom of the slab that is usually described as the tension face.

In one way slab, as one side is larger as compared to the other one, the greatest load is carried by the larger side. To give more support on the larger side, main reinforcement is set perpendicular to that side or parallel to the shorter direction. Distribution steel is arranged in the extended direction that will not be very useful for carrying any load.

In one way slab, the main reinforcement is calculated with a formula (In limit state design) and to obtain the result the comparison is made between the comparing compressive force and tensile forces.

Ast = 0.5 Fck/Fu[1-√1-2.6Mu/Fck.b.d]b.d

and the distribution steel is calculated as

0.15% of Ag, for mild steel.

0.12% of Ag, for tor steel.

Where, Ast denotes Area of the steel in tension.

Fu denotes Ultimate strength of steel.

Mu denotes Ultimate moment of resistance.

b denotes Breadth of the slab section.

d denotes Depth of the slab section.

Ag denotes Gross area of the section.

Article Source : www.dailycivil.com

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Published By

Rajib Dey

www.constructioncost.co

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Benefits And Drawbacks Of Flab Slabs Toward Flab Slab Floor System

A flat slab belongs to a one-way or two-way method that is condensed in the slab at the columns and load bearing walls known as ‘drop panels’. Drop panels are used as T-beams over the supports. They improve the shear capacity and the rigidity of the floor system below vertical loads, which consequently enhance the economical span range. Now-a-days, this type of construction is not recommended as the perimeter on economical spans is approximately 9.5 m for reinforced slabs and approximately 12 m for pre-stressed slabs. Reinforced flat slabs should be reasonably pre-cambered (not overdone) to manage deflection.

The primary features of a flat slab floor are a flat soffit, plain formwork and simple construction. The economical span ‘L’ of a reinforced concrete flat slab is roughly D x 28 for simply supported, D x 32 for an end span and D x 36 for an interior span. Prestressing the slab expands the economical span to D x 35, D x 40 and D x 45 correspondingly, where D denotes the depth of the slab exclusive of the drop panel.

Benefits and Drawbacks of Flat Slabs

Benefits :

• Uncomplicated formwork

• No beams—make things easier under-floor services outside the drops

• Lowest structural depth

• Generally no need of shear reinforcement at the columns.

Drawbacks:

• Moderate spans

• Usually not appropriate for supporting brittle (masonry) partitions

• Drop panels hinder in bigger mechanical ducting

• Vertical penetrations should prevent area around columns

• For reinforced flat slabs, deflection at the middle strip becomes complicated.

Ref.: civildigital.com

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Published By

Rajib Dey

www.constructioncost.co

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