Conventional Slab (solid Slab)
The slab which
is supported on Beams and columns is called conventional slab. In this kind,
the thickness of slab is small whereas depth of the beam is large and load is
transferred to beams and then to columns. It requires more formwork when
compared with the flat slab. In conventional type of slab there is no need of
providing column caps. The thickness of
conventional slab is 4″ or 10cm. 5″ to 6″ inches is recommended if the concrete
will receive occasional heavy loads, such as motor homes or garbage trucks.
Conventional
concrete slabs are square in shape and has a length of 4m. Reinforcement is
provided in conventional slab and the bars which are set in horizontal are
called Main Reinforcement Bars and bars which are set in vertical are called
Distribution bars.
Based on
length and breadth of Conventional Slab is classified into two types:
u1.One-Way Slab.
u2.Two-Way Slab.
1. One Way
Slab:
One way slab
is supported by beams on the two opposite sides to carry the load along
one direction. The ratio of longer span (l) to shorter span (b) is equal or
greater than 2, considered as One-way slab. In this type slab will bend in one
direction i.e. in the direction along its shorter span. However minimum
reinforcement known as distribution steel is provided along the longer span
above the main reinforcement to distribute the load uniformly and to resist
temperature and shrinkage stresses.
In general
length of the slab is 4m. But in one way slab one side length is 4m and another
side length is more than 4m. So it satisfies the above equation. Main
reinforcement is provided in shorter span and distribution reinforcement is
provided in longer span. Distribution bars are cranked to resist the formation
of stresses.
Example: Generally all the Cantilever slabs are one
Way slab. Chajjas and verandahs
are a practical example of one way slab.
2. Two Way
Slab:
Two way slab
is supported by beams on all the four sides and the loads are carried by the
supports along both directions, it is known as two way slab. In two way slab,
the ratio of longer span (l) to shorter span (b) is less than 2. The slabs are
likely to bend along both the directions to the four supporting edges and
hence distribution reinforcement is provided in both the directions.
In this kind
of slab, the length and breadth of the slab are more than 4m. To resist the
formation of stresses distribution bars are provided at both the ends in two
way slab.
These types of
slabs are used in constructing floors of multi-story building.
ADVANTAGES
uHigh span time
due to relatively deep beams.
uResisting
lateral loads due to the beams.
uSlab is light
due to the relatively less thickness.
uPunching shear
failure is not crucial.
DISADVANTAGES
uFloor to floor
height is high which increases the building height.
uBeans disturb
the air circulation and light in the building.
uFormwork is
complex.
uReinforcement
is complex.
uConstruction
time is high.
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