Types And Classifications Of Slabs
Slabs could be classified
in various ways. The way you classify a slab, depends on the features you want
to put into consideration.
For instance, slabs could
be classified based on the materials they are made of such as concrete slab,
steel slab or composite slab.
As the names suggest, concrete slabs are made
of concrete (mixture of water, cement, fine aggregates and coarse aggregates),
steel slabs are made of steel while composite slabs are made of combinations of
various materials: e.g., steel and concrete.
Slabs could also be
classified based on the support type: e.g., simply supported slabs and
A continuous slab spans across more than two supports, whereas for a simply supported slab, there are
supports at the two opposite edges only. In this case, no moment occurs at the
edges and the critical section for design, is the midspan.
For a restrained slab, the edges are held
down firmly at the supports and develop hogging or negative moments. Here too,
moment coefficients are given in the code for positive and negative moments.
Consequently, slabs could
be classified based on the geometry e.g., circular slab. As the name implies, a circular slab is circular or round in
A flat slab has no beams at the supports all through the geometry of
the slab. It is usually supported on columns which may or may not have column
capitals. The columns themselves are connected to the drop panels of the slab
to reduce punching shear.
A flat plate is also a type of flat slab which usually has no drop
panels. It rests directly on columns hence, serious punching shears develop at
the supports, most especially when they carry enormous stresses. This makes
flat plates unsuitable for large spans.
A stair case slab is a special case of one – way slab. They are found
mainly where there are stairs.
The self-weight of the
flight of steps in open-well and dog-leg stairs is calculated on the basis of
slope length while imposed load is based on the plan length.
The positive moment
coefficients for these stairs are 0.10 for stair slab, either fixed or continuous,
and 0.125 for one with no appreciable restraint.
A hollow slab usually has opening within it.
Other types of slabs
include ribbed slab which has ribs
running in one direction, usually along the span. It is also a special case of
When the ribs run in both
directions, forming dome-like structures, the slab type is a waffle slab. The forms for a waffle
slab could be formed using steel pan forms, with timber falsework. A waffle slab is simply a two way ribbed slab.
A solid slab is a very common type of slab. It normally has beams
running across supports. The beams transfer the slab loads to the columns.
Slabs could also be
classified based on their locations or where they are used:
A grade or ground slab usually forms part of the foundation on or
within the ground, as is the case with a raft foundation.
A floor slab is any slab used in the floor of a building. It forms
the floor for any of the storeys of a building.
A roof slab is any slab located at the roof of a building.
These are the various
types of slabs used in a building. Did I omit any that you know, then let me know in the comment section below.
Originally posted on May 22, 2020 @ 8:57 am