Flat Slab - Types of Flat Slab Design and Its Advantages

Flat Slab – Types of Flat Slab Design and
its Advantages
Home » Flat Slab – Types of Flat Slab Design and its Advantages
Flat slab is a reinforced concrete slab supported directly by concrete columns

without the use of beams. Flat slab is defined as one sided or two-sided
support system with sheer load of the slab being concentrated on the
supporting columns and a square slab called ‘drop panels’.
Drop panels play a significant role here as they augment the overall capacity
and sturdiness of the flooring system beneath the vertical loads thereby
boosting cost effectiveness of the construction. Usually the height of drop
panels is about two times the height of slab.
Flat Slabs are considered suitable for most of the construction and for
asymmetrical column layouts like floors with curved shapes and ramps etc.
The advantages of applying flat slabs are many like depth solution, flat soffit
and flexibility in design layout.
Even though building flat slabs can be an expensive affair but gives immense
freedom to architects and engineers the luxury of designing.
Benefit of using flat slabs are manifold not only in terms of prospective
design and layout efficacy but is also helpful for total construction process
especially for easing off installation procedures and saving on construction
time.
If possible, try to do away with drop panels as much as possible and try to
make the best use of thickness of flat slabs. The reason is to permit the
benefits of flat soffits for the floor surface to be maintained, ensure drop
panels are cast as part of the column.
To utilize the slab thickness to optimum level, the essential aspects that should be kept in
mind are:
1. Procedure related to design
2. Presence or absence of holes
3. Significance of deflections
4. Previous layout application experience
Types of Flat Slab Construction

Following are the types of flab slab construction:
o Simple flat slab
o Flat slab with drop panels
o Flat slab with column heads
o Flat slab with both drop panels and column heads
Uses of Column Heads

o It increase shear strength of slab
o It reduce the moment in the slab by reducing the clear or effective span
Uses of Drop Panels

o It increase shear strength of slab
o It increase negative moment capacity of slab
o It stiffen the slab and hence reduce deflection
Advantages of Flat Slabs

It is recognized that Flat Slabs without drop panels can be built at a very fast
pace as the framework of structure is simplified and diminished. Also, speedy
turn-around can be achieved using an arrangement using early striking and
flying systems.
Flat slab construction can deeply reduce floor-to –floor height especially in the
absence of false ceiling as flat slab construction does act as limiting factor on
the placement of horizontal services and partitions. This can prove gainful in
case of lower building height, decreased cladding expense and pre-fabricated
services.
In case the client plans changes in the interior and wants to use the
accommodation to suit the need, flat slab construction is the perfect choice
as it offers that flexibility to the owner. This flexibility is possible due to the
use of square lattice and absence of beam that makes channelling of
services and allocation of partitions difficult.
Thickness of flat slab
Thickness of flat slab is another very attractive benefit because thin slab
provides the advantage of increased floor to ceiling height and lower
cladding cost for the owner. However, there is profound lower limit to
thickness of slab because extra reinforcements are needed to tackle design
issues. Besides this, added margin must be provided to facilitate
architectural alterations at later stages.
Types of Flat Slab Design
Multitudes of process and methods are involved in designing flat slabs and
evaluating these slabs in flexures. Some of these methods are as following:
o The empirical method
o The sub-frame method
o The yield line method
o Finite –element analysis

For smaller frames, empirical methods are used but sub-frame method is used in
case of more irregular frames. The designs are conceptualized by employing
appropriate software but the fact is using sub-frame methods for very
complicated design can be very expensive.
The most cost effective and homogenous installation of reinforcements can
be achieved by applying the yield line method. A thorough visualization in
terms of complete examination of separate cracking and deflection is
required since this procedure utilises only collapse mechanism.
Structures having floors with irregular supports, large openings or bears
heavy loads, application of finite- element analysis is supposed to be very
advantageous. Great thought is put into choosing material properties or
installing loads on the structures. Deflections and cracked width can also be
calculated using Finite- element analysis.
Areas That Require Attention in Design of Flat Slab
1. Deflections-Usually at the center of each panel deflections are maximum.
Foreseeing deflections can be very tricky and will engage some form of
elastic appraisal. While designing structure layout and during
implementation using sub frame method, one way to evaluate mid-panel
deflection is to use at least two parallel column strips.
2. Proprietary punching sheer reinforcement systems- In case of thin flat slab
construction punching sheer reinforcements are indispensable.
3. Optimization of Main reinforcement- In certain design procedures, especially in
yield line output is better optimized than in other design methods.
Benefits of Using Flat Slab Construction Method
o Flexibility in room layout
o Saving in building height
o Shorter construction time
o Ease of installation of M&E services
o Use of prefabricated welded mesh
o Buildable score
Flexibility in Room Layout

Flat slabs allows Architect to introduce partition walls anywhere required,
this allows owner to change the size of room layout. Use of flat slab allows
choice of omitting false ceiling and finish soffit of slab with skim coating.
Saving in Building Height

o Lower storey height will reduce building weight due to lower partitions and
cladding to façade
o Approximately saves 10% in vertical members
o Reduced foundation load
Shorter Construction Time

Use of flat slabs requires less time for construction by the use of big table
formwork.
Single Soffit Level
Ease of Installation of Flat Slabs

All M & E services can be mounted directly on the underside of the slab
instead of bending them to avoid the beams.
Use of Prefabricated Welded Mesh

Use of prefabricated welded mesh minimizes the installation time of flat
slabs. These mesh are available in standard size and provides better quality
control in construction of flat slab.
Buildable Score
This allows standardized structural members and prefabricated sections to
be integrated into the design for ease of construction. This process makes
the structure more buildable, reduce the number of site workers and
increase the productivity at site, thus providing more tendency to achieve a
higher Buildable score.

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Flat Slab – Types of Flat Slab Design and

Flat slab is a reinforced concrete slab supported directly by concrete columns

2. Presence or absence of holes

4. Previous layout application experience

Types of Flat Slab Construction

o Simple flat slab

o Flat slab with drop panels

o Flat slab with column heads

o Flat slab with both drop panels and column heads

Uses of Column Heads

Uses of Drop Panels

o It stiffen the slab and hence reduce deflection

Advantages of Flat Slabs

o The empirical method

o The sub-frame method

o The yield line method

o Finite –element analysis

o Saving in building height

o Shorter construction time

o Ease of installation of M&E services

o Use of prefabricated welded mesh

Flexibility in Room Layout

Saving in Building Height

o Approximately saves 10% in vertical members

o Reduced foundation load

Shorter Construction Time

Ease of Installation of Flat Slabs

Use of Prefabricated Welded Mesh

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