Seismic Analysis of Multi Storied Irregular Building using Flat Slab and Grid Slab in Zone III & V

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 06 | June -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 664
Seismic Analysis Of Multi Storied Irregular Building Using Flat Slab
And Grid Slab In Zone III & V
Reshma R1, Arunima V R2
1PG Scholar, Department of Civil engineering SBCE Elavumthitta, Pathanamthitta, Kerala, India
2 Assistant Professor, Department of Civil engineering SBCE Elavumthitta, Pathanamthitta, Kerala, India
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Abstract - As of late there has been a significant increment in
the quantity of tall structures, both private and business, and
current pattern is towards taller structures. The Flat section
arrangement of development is one in which the pillar is
utilized as a part of the regular techniques for development
discarded the specifically lays on segment and the heap from
the pieces is straightforwardly exchangedtothesegmentsand
afterward to the establishment. To enhance the execution of
building having level pieces under seismic stacking,
arrangement of level section with drop is proposed. Drops or
segments are for the most part given segment heads or
capitals. Network floor frameworks comprising of shafts
separated at customary interims in opposite bearings, solid
with chunk. They are by and large utilized for compositional
explanations behind substantial rooms, for example,
amphitheaters, vestibules, theater lobbies, indicate rooms of
shops where section free space is frequently the fundamental
necessity. The protest of the present work is toconcentratethe
conduct of multi-story structures having level sections with
drops network piece framework under direct powerful
examination (Response range investigation) in two distinct
zones i.e. zone III and zone V with medium soil sort conditions.
Programming ETABS is utilized for this reason. The
parameters of this study are Base shear
Key Words: flat slab, drop, conventional slab, storey
shear, ETABS
1. INTRODUCTION
The rapid growth of the urban population and scarcity of
space have considerable influence the development of
vertical growth consisting of low rise, medium rise and high
rise buildings. Generally reinforced concrete is the major
construction material used for these buildings and it has
been used for building construction since 19th century.
Reinforced concrete structures are always subjected to
gravity and lateral loads, that is live load, dead load,
superimposed load, and lateral loads are such as seismic
load and wind load. Previously buildings were designed for
only gravity loads that may not have resistance to lateral
loads. In reinforced concrete structures horizontal loadsare
first which will increase proportionally with increase floor
height of the buildings as a result lateral loads are higher in
the top storey compare to the bottom storey due to which
building tends to act as cantilever and that forces develop
high stresses, produce sway movement leads to severe
damages and hence at last failure of buildings. The failure of
buildings occurs mostly in theseismicproneareaswhere the
structures are not well designed for earthquake load and
wind loads. Therefore, it is very much necessary to design
the structures to have sufficient stiffness to resist the lateral
forces. For this purpose an earthquake resistant design of
reinforced concrete structures is a current part of research
across the world. The main purpose of this earthquake
resistant design of reinforced concrete research is to design
structural members of building like column, beam, and slab
withstand against the dynamic forces and make sure the
building should be safe and stiff under effect of worst
condition. Usually in reinforced concrete buildings to resist
against lateral load, sometimes a structural members are
modified that may be column, beam and slab, but in this
project is more concern about slabs. Generally there is so
many types of slab but here will discuss about two different
type of slabs that is flat slab and grid slab
2. OBJECTIVES
The main purpose of this analysis is to study thecomparison
between grid slab and flat slab with drop structures for
various seismic parameters such as
1. To study the maximum base shear of flat slabandgridslab
of RCC structure for zone III and zone V
3. BUILDING PLAN AND DIMENSIONAL DETAILS
The building is modeled using the flat slab and grid slab
feature in ETABS. The span lengths in X and Y are specified.
Storey height and number of floorsare entered. Thematerial
properties and section properties are defined for the slab,
column and beam. The complete detail of the structure is
given in Table 4.1.Table 1: Details and dimension of the
building models
Number of stories 15
Seismic zone III & V
Floor height 3 m
Grade of Concrete M40
Grade of steel Fe 500
Beam dimension 450mm x 600mm
Column dimension 600mm x 900mm

Slab thickness 125mm
Flat slab thickness 200 mm
Size of drop 350 mm
Dead load 1 kN/m2
Live load : 3 kN/m2
Importance factor(IF): 1.5
Fig.1 Plan of T shaped building with grid slab
Fig 2 3D View of T shaped building with grid slab
Fig.3 Plan of T shaped building with flat slab
Fig 4 3D View of T shaped building with flat slab
Fig.5 Plan of L shaped building with grid slab
Fig.6 3D view of L shaped building with grid slab

Fig.7 Plan of L shaped building with flat slab
Fig.8 3D view of L shaped building with flat slab
4. ASSIGNING LOADS
 Dead Load
Slab Weight calculation:
Thickness of slab = 0.125m
Density of concrete = 25kN/m3
Self-weight of slab = Density of concrete x Thickness
of
= 25x0.125 = 3.125kN/m2
Floor Finish load calculation:
Floor load = Density of floor material x
thickness of floor
= 20 x 0.05 = 1 kN/m2
 Live Load
Floor load:
Live Load Intensity specified (Commercial building) =
4kN/m2(IS: 875 (Part 2) – 1987)
Live Load at roof level = 1.5 kN/m2
 Load Combinations
Following are the load combinations provided for each
models for the analysis purposes.
1. DL
2. DL+LL
3. 1.5(DL+LL)
4. 1.2(DL+LL+ELX)
5. 1.2(DL+LL+ELY)
6. 1.2(DL+LL-ELX)
7. 1.2(DL+LL-ELY)
8. 1.5(DL+ELX)
9. 1.5(DL+ELY)
10. 1.5(DL-ELX)
11. 1.5(DL-ELY)
12. 0.9DL+1.5ELX
13. 0.9DL+1.5ELY
14. 0.9DL-1.5ELX
15. 0.9DL-1.5ELY
5. ANALYSIS
After assigning the loads to the structure, Response
spectrum analysis is carried out to evaluate the shear force
bending moment, axial force and dynamicresultsintheform
of storey shear.
Response spectrum analysis
The response spectrum represents an envelope of upper
bound responses based on several different ground motion
records. For the purpose of seismic analysis, the design
spectrum given in Figure 1 of IS: 1893 (Part 1): 2002 isused.
This spectrum is based on strong motion records of eight
Indian earthquakes. This method is an elastic dynamic
analysis approach that relies on the assumption that the
dynamic response of the structure can be found by
considering the independent response of each natural mode
of vibration and then combining the response of each in the
same way. This is advantageous in the fact that only a few of
the lowest modes of vibration have significance while
calculating moments,shearanddeflectionsatdifferentlevels
of the building.

Fig.9 Response Spectrum Curve
Analysis results
From the output of ETABS, various results are obtained.
And these results are tabulated and evaluated by
preparing various graphs.
Storey Shear
The base shear is a estimate of the maximum expected
lateral force that will occur due to the seismic ground
motion at the base of a structure. Calculations of base
shear depend on soil conditions at the site, proximity to
potential sources of seismic activity
Table 4 Maximum Storey Shear for plan irregular
Buildings with flat slab and grid slab in zone V
FLAT SLAB GRID SLAB
L T L T
Zone
5
X 6254.45 6257.86 7568.92 7544.00
9
Y 4097.4 6032.6 7165.8 7488.01
Fig 10 Maximum Storey shear in zone V for different
types of structures with flat slab and grid slab
Table 5 Maximum storey shear in zone III for different
types of buildings with flat slab and grid slab
FLAT SLAB GRID SLAB
L T L T
Zone
3
X 2779.75 2781.271 3363.96 3352.89
Y 1821.08 2681.16 3184.82 3284.23
Fig 11 Maximum Storey Shear in zone III for different
types of structures with flat slab and grid slab
6. CONCLUSIONS
In this the seismic analysis is carried out to study the
comparison between flat slab with drop structures and grid
slab structures under different conditions for different
parameters and from the above results it can be concluded
that
1. Grid slab structures have maximum base shear in
comparison with flat slab with drop in both zones
ACKNOWLEDGEMENT
The authors can acknowledge any person/authoritiesinthis
section. This is not mandatory.
REFERENCES
[1] Apostolska et al. (2008), “Use of flat slabs in multi-
storey commercial building situated in high seismic zone”,
Vol.03, No. 08, IJRET: International Journal of Research in
Engineering and Technology
[2] Bothara and Varghese (2012),”Dynamic analysis of
multi-storey RCC building frameWithflatslabandgridslab”,
Al Int. Journal of Engineering ResearchandApplications, Vol.
4, No. 2, Version 1, pp. 416-420.
[3] Sable et al. (2012),”Comparative study of RC flat slab
and shear wall with conventional framed structure in high

rise building”,Volume No.05, International Journal of
Engineering Research.
[4] Navyashree K and Sahana T S (2014), “Parametric
study of flat slab building with and without shear wall to
seismic performance”, Vol.04, No. 04, IJRET: International
Journal of Research in Engineering and Technology.
[5] Basavaraj and Rashmi B. A (2015),“Seismic behaviour
of flat slab framed structure with and without masonry infill
wall”, Vol.02, No. 07, IJRET:International Journal ofResearch
in Engineering and Technology

Seismic Analysis of Multi Storied Irregular Building using Flat Slab and Grid Slab in Zone III & V

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