INTERNATIONAL JOURNAL
OF PROFESSIONAL ENGINEERING STUDIES Volume VIII /Issue 3 / MAR 2017
ANALYSIS AND DESIGN OF REGULAR AND IRREGULAR FLAT SLAB FOR
MULTISTOREYED BUILDING UNDER TWO SEISMIC ZONES USING ETABS AND SAFE
THIMMAYAPALLY DILEEP KUMAR1, A.MOWNIKA VARDHAN2
1
M. Tech (Structural Engineering), Department of Civil Engineering, Vishwa Bharathi College of Engineering
Adj. Brundavan colony, Nizampet road, Opp. JNTUH, Kukatpally, Hyderabad-500085,
2
Assistant Professor (M.Tech), Department of Civil Engineering, MVR College of Engineering and Technology,
Adj. Brundavan colony, Nizampet road, Opp. JNTUH, Kukatpally, Hyderabad-500085
ABSTRACT: connecting together and stiffening the various
vertical frame elements. Under the action of lateral
Construction industry is being revolutionised with
loads, the floor diaphragms behave rigidly (owing to
growing technology and innovation. Man started to reach
its high in plane flexural stiffness) and effectively
sky not in any aeroplane but with the height of building.
distribute the lateral load to the various vertical frame
Tall structures have considerably reduced the problem of
shelter but are considered highly susceptible to seismic
elements and shear walls. In cast in situ reinforced
loads and uneconomical. Both the problems are aroused concrete construction the floor system usually
due to high weight of the building. Of all the structural consists of one of the following
members in a building slabs are considered to be
occupying high area and the load of the building is mostly
contributed due to slab. In general for commercial areas
normal slabs are not been considered, as the spans
between the supports are more which leads to increasing
in deflection and ultimately provision of huge depth and
percentage of steel is increased beyond the codal
provision ,once such solution to reduce the slab depth and
provide economical design is flat slabs technology.
Wall Supported slab systems
I.INTRODUCTION:
The horizontal floor system resists the
gravity load (dead load and live load) acting on it and
transmits this to the vertical framing systems. In this
process, the floor system is subjected primarily to
flexure and transverse shear, whereas the vertical
frame elements are generally subjected to axial
compression, often coupled with flexure and shear.
The floor also serves as a horizontal diaphragm
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Beam Supported Slab System supporting column. Drop panels or simply drops are
provided mainly for the purpose of reducing shear
stress around the column supports.
Column Capital: The column capital or column head
provided at the top of a column is intended primarily
to increase the capacity of the slab to resist punching
shear. The flaring of the column at top is generally
done such that the plan geometry at the column head
is similar to that of the column.
Two way ribbed (waffle) slab system
Drop panel and column capital
Types of FLAT SLAB:
1. FLAT PLATE
Flat Slab Systems
RC slabs with long spans extended over several bays
and only supported by columns, without beams
known as flat slab. Flat slab system is very simple to
construct and is efficient in that it requires the
minimum building height for a given number of
2. FLAT PLATE WITH COLUMN HEAD OR
stories. Such structure contains large bending
moment and vertical forces occur in a zone of CAPITAL
supports. This gives a very efficient structure which
minimizes material usages and decreases the
economic span range when compared to reinforced
concrete. Post-tensioning improves the structural
behaviour of flat slab structure considerably. This is
more acceptable concept to many designers. It is
adopted in some office buildings.
Drop Panels: The 'drop panel' is formed by the local
thickening of the slab in the neighbourhood of the
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3. FLAT PLATE WITH DROP systems which is presented in the paper show that flat
slab system with certain modifications (design of
beam in the perimeter of the building and/or RC
walls) can achieve rational factor of behaviour
considering EC8 and can be consider as a system
with acceptable seismic risk. Modifications with
additional construction elements improve small
bearing capacity of the system and increase strength
and stiffness, improving seismic behaviour of flat-
slab construction system. Selected result from the
analysis is presented in the paper.
4. FLAT PLATE WITH DROP AND COLUMN
HEAD
Mohd. Rizwan Bhina1, Waseem Khan2,
and D.K.Paul3
Flat-Slab building is very popular from the aesthetic
and architectural point of view. From functional
aspect a flat-slab building is more efficient than a
R.C. frame building. So, construction of Flat-Slab
building is increasing also in high seismic zone.. In
this paper the response of Flat-Slab building and a
normal symmetric R.C. frame building of same
dimension have been studied for varying seismic
intensities and serviceability. Static, Response
II.LITERATURE REVIEW
Spectrum, have been performed to assess the
1 2
R. P. Apostolska , G. S. Necevska-Cvetanovska , performance of buildings. The costs of construction
3 4
J. P.Cvetanovska and N. Mircic : for these two buildings have also been compared. An
extensive study of serviceability has also discussed in
Flat-slab building structures possesses major
the paper. The paper also comments on the cost of the
advantages over traditional slab-beam-column
flat slab building and conventional building and there
structures because of the free design of space, shorter
serviceability. Papers also conclude that which
construction time, architectural –functional and
building is more serviceable during earthquake.
economical aspects. Because of the absence of deep
beams and shear walls, flat-slab structural system is S.D.Bothara et.al
significantly more flexible for lateral loads then
traditional RC frame system and that make the Studies about comparative effect of earthquake on
system more vulnerable under seismic events. The flat slab & Grid floor system consisting of beam
results from the analysis for few types of construction
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spaced at regular intervals in perpendicular span to effective depth ratio. For this purpose larger
directions, monolithic with slab. span is to be considered. If drop as specified in 3.2.1
is provided, then the maximum value of ratio of
V.K. Rahman1 et.al work on design of R.C.C. as
larger span to thickness shall be
well as pre-stressed concrete flat slabs for various
spans and then compare the results. Programming in = 40, if mild steel is used
MS EXCEL is done to design both types of flat slabs. = 32, if Fe 415 or Fe 500 steel is used
The idea is to reach a definite conclusion regarding If drops are not provided or size of drops do not
the superiority of the two techniques over one satisfy the specification 3.2.1, then the ratio shall not
another. Results reveal that a R.C.C. flat slab is exceed 0.9 times the value specified above i.e.,
cheaper than pre-stressed concrete flat slab for
= 40 X 0.9
smaller spans but vice versa is true for larger span.
= 36, if mild steel is used.
III PROPORTIONING OF FLAT SLABS:
= 32 X 0.9
IS 456-2000 [Clause 31.2] gives the following = 28.8, if HYSD bars are used
guidelines for proportioning. It is also specified that in no case, the thickness of
flat slab shall be less than 125 mm.
DROPS
The drops when provided shall be INTRODUCTION TO SOFTWARES
rectangular in plan, and have a length in each
ETABS:
direction not less than one third of the panel in that
direction. For exterior panels, the width of drops at The innovative and revolutionary new ETABS is the
right angles to the non-continuous edge and ultimate integrated software package for the
measured from the centre-line of the columns shall be structural analysis and design of buildings.
equal to one half of the width of drop for interior Incorporating 40 years of continuous research and
panels. development, this latest ETABS offers unmatched 3D
object based modeling and visualization tools,
COLUMN HEADS blazingly fast linear and nonlinear analytical power,
Where column heads are provided, that sophisticated and comprehensive design capabilities
portion of the column head which lies within the for a wide-range of materials, and insightful graphic
largest right circular cone or pyramid entirely within displays, reports, and schematic drawings that allow
the outlines of the column and the column head, shall users to quickly and easily decipher and understand
be considered for design purpose as shown in Figs. analysis and design results.
3.2 and3.4.
SAFE:
Thickness of flat slab
SAFE is the ultimate tool for designing
From the consideration of deflection control
concrete floor and foundation systems. From framing
IS 456-2000 specifies minimum thickness in terms of
layout all the way through to detail drawing
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production, SAFE integrates every aspect of the DESIGN OUT PUT:
engineering design process in one easy and intuitive
PUNCHING SHEAR:
environment. SAFE provides unmatched benefits to
the engineer with its truly unique combination of
power, comprehensive capabilities, and ease-of-use.
IV MODEL IN ETABS AND SAFE:
ETABS:
Punching shear: Max of =0.9885 which is less than 1 safe
SAFE:
EXPORT TO SAFE
BENDING MOMENT IN THE STRIPS
CELLER FLOOR PLAN IN SAFE
AREA OF STEEL ALONG THE STRIPS Y- AXIS
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CELLAR PLAN:
AREA OF STEEL ALONG THE STRIP X-AXIS
V DRAWINGS:
FOUNDATION DETAILS:
COLUMN DETAILS:
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FLOOR PLAN: VI RESULTS:
STRIP FORCES
FOUNDATION REACTIONS:
DESIGN OF FOUNDATION:
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DISPLACEMENT: COLUMN DESIGN:
CONCLUSIONS
1. Flat-slab building structures possesses major
advantages over traditional slab-beam-column
structures because of the free design of space, shorter
BEAM DESIGN: DESIGNED FOR CRITICAL construction time, architectural –functional and
LOAD ONLY BEAM 40 economical aspects.
2. Because of the absence of deep beams and shear
walls, flat-slab structural system is significantly more
flexible for lateral loads then traditional RC frame
system and that make the system more vulnerable
under seismic events.
3. The purely flat-slab RC structural system is
considerably more flexible for horizontal loads than
the traditional RC frame structures which contributes
to the increase of its vulnerability to seismic effects.
4. The critical moment in design of these systems is
the slab-column connection, i.e., the penetration force
in the slab at the connection, which should retain its
bearing capacity even at maximal displacements.
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5. The ductility of these structural systems is [7] The other code books referred for this project are,
generally limited by the deformability capacity of the SP 16 (design aids for IS 456), IS 875 – Part I, II, III,
column-slab connection. V.
6. To increase the bearing capacity of the flat-slab [8] Mahdi hosseini , Ahmed najim Abdullah
structure under horizontal loads, particularly when alaskari,Prof.N.V.RamanaRao, International Journal
speaking about seismically prone areas and limitation of Civil Engineering and Technology (IJCIET), ISSN
of deformations, modifications of the system by 0976 –6316(Online), Volume 5, Issue 8, August
adding structural elements are necessary. (2014).
REFERENCE:
[1] ISSN 2321-6905 (Paper) IJSEAT, Vol 4, Issue 2
,2016 “Analysis and Design of Flat Slabusing Etabs
Software” by B. Anjaneyulu et al.
[2] Sunayana Varma , B. Venugopal, K. Karthikeyan
International Journal of Civil Engineering and
Technology (IJCIET), ISSN 2321 –919X(Online),
Volume 2, Issue 8, August (2014)
[3] Mahdi hosseini , Ahmed najim Abdullah
alaskari,Prof.N.V.RamanaRao, International Journal
of Civil Engineering and Technology (IJCIET), ISSN
0976 –6316(Online), Volume 5, Issue 8, August
(2014).
[4] CSI, (2011), extended 3D analysis of building
structures (ETABS), Computers and Structures Inc.,
USA
[5] IS: 1893 (Part 1), (2002), Indian Standard Criteria
for Earthquake Resistant Design of Structures,
Bureau of Indian Standards, New Delhi.
[6] IS: 456:2000, Indian Standard Code of Practice
for Plain and Reinforced Concrete, Bureau of Indian
Standards, New Delhi.
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