Comparison III. KEYWORDS: Flat Slab, Conventional Two Way

Comparison between flat and Conventional
slab of high rise buildings with varying geometry under seismic loading
condition

 

SOHAN LAL

*M. Tech. Student of Patel Institute of
Engineering & Science Bhopal M.P. India.*

Email: [email protected]

Mr. Vinay Kumar Singh Chandrakar

**Faculty Of Civil Engg. Department**

Email: [email protected]

                                                          
 Prof. J. P. Gupta

**H. O. D. Of Civil Engg. Department**

Email: [email protected]

 

 

 

1           
  ABSTRACT

This paper focuses on comparative study in the behavior of high rise
building structures under seismic loading condition and wind pressure by using
different types of slabs in various types of geometries. The whole analysis is
done by taking conventional slab and flat slab in various geometries and various
floors separately. The parametric studies comprise of maximum lateral
displacement, beam shear, storey drift and axial forces generated in the beam
and column. For these case studies we have created 18 models for conventional
two-way slabs and flat slab without shear wall in rectangular, hexagonal and
octagonal geometry. The modelling is done in STAAD.pro V8i for seismic zones
III and rectangular, hexagonal and octagonal geometries have considered for
analysis. Plan size of rectangle 16X28 m, Hexagonal 16 m in diameter, and
octagonal 12 m in diameter have considered. The models have also
developed for different number of floors taking G+9, G+15 and G+23 storey for
all above geometries. Seismic loadings, wind loadings are considered separately
to evaluate the performance of all the 18th models
and conclusions have drawn on the best slab framing system. Hence a deep comparative
study is done to identify the best slab system in seismic zone III.

 

KEYWORDS:
Flat Slab, Conventional Two Way Slab, RCC Structure, Design & STAAD.pro V8i

1           
INTRODUCTION

There is an increasing demand for
construction of high rise buildings due to urbanization and an ever increasing
population. Earthquake and wind pressure are the biggest enemy of such tall
structures. These earthquake forces are hazard in nature and are thus
unpredictable. The structure designers needs to analysing the structures under
the action of these seismic forces and varying wind intensity. Thus a careful analysis
is required of such loads, so as to evaluate the external forces on tall
structures with a clear perspective of the damage that is to be expected.  The structures are analysed for various
earthquake intensities and wind intensities then apply check for various performing
criteria at each level. It is become an essential practice for the last some decades
occurs in the century. Hence the seismic characteristics and wind
characteristics of buildings having same layout needs to be understood under various
different intensities of earthquake. It is necessary to carry out seismic
analysis and wind analysis of the building structure using different  methods for determination of seismic characteristic
and wind characteristic  in structure. 

The main objective of this paper is to analysis
and comparison between flat slabs and conventional two way slabs using
STAAD.proV8i, to get the best slab system. The design involves various load
calculations, beam shear, beam moment and nodal deflection and analysing the
whole structure by STAAD.pro V8i using Limit State Design method using Indian
Standard Code of Practice (IS: 456-2000). The STAAD.pro features are to
state-of-the-art user interface, and powerful analysis and design engines. It
offers visualization tools, modelling tools and advanced finite element &
dynamic analysis capabilities. STAAD.pro offers a very interactive user
interface which allows the users to draw the new frame section and input the
member property, element property, supports and load values. Then according to
the specified assigned property of the structure, it analyses the structure and
finally designs the all members with reinforcement details for RCC frames.

2.1           
STAAD-pro V8i

STAAD pro is the leading Structural analysis
and Design Software developed in Yorba Linda, CA by Research Engineers
International. In the late months of year 2005, Research engineer was brought
by Bentley Systems. The professional version STAAD.PRO is few of the majorly
used structural design and analysis software. It is quite user friendly and
supports a number of steel, concrete and timber design codes. It can make
utilization of different manifestations of structural analysis from the
conventional first order static analysis, second order p-delta investigation
and geometrical non-linear analysis.

2.2     FLOOR SYSTEMS:-

Slabs are used as flat surfaces, usually horizontal in building, floors,
roofs, bridges slab and many other types of structures. The slab may be
supported on directly walls, on reinforced concrete beams usually cast monolithically
with the slab, on structural steel beams, on directly columns, or on the ground
surface. Slabs may be classified in different 16 types used in different
structures. Flat slab and conventional slab are one of them. Which are
discussed below:-

2.2.1  Flat
Slab Floor System-

Flat slab is a
reinforced concrete element supported directly on concrete columns or on the
drop panels used above the columns. There are no beams in a flat slab. Slab is
supported directly on columns itself and all applied loads are transferred to directly
columns. In flat slab construction there are a plain ceiling is obtained and
hence it offers attractive appearance from architectural point of view. The
construction of flat slab is easy and economical compare to other beam slabs and
requires less formwork. And also required less time for construction compare to
other beam slabs. The light is diffuses better by plain ceiling and also less
vulnerable in the case of fire compare to other beam slabs The flat slab is
easier to construct. The thickness of Flat slab is provided minimum 8? or 0.2m.

                                                       

2.2.2  Conventional
Slab Floor System:-

The slab which is
supported with Beams is known as conventional slab. In conventional slab the
thickness provided is small and depth of beam is provided large and hence all loads
are transferred to beams, to Columns and then finally to foundations. It
requires more time for construction as formwork increases compared to the flat
slab system. The thickness of conventional slab is provided as 5? to 6?or 150
mm.  The main reinforcement is provided
in conventional slab in one direction or in both direction according to length
and breadth of Conventional Slab. Based on the length and breadth of
Conventional Slab is classified into two types: These types of slabs are used
in constructing floors of multistory building.

 

 

Classification of Conventional Slab:-

One-Way
Slab

Two-Way
Slab

 

2.3     OBJECTIVE
OF STUDY:-

Ø  Analysis
of multi storied RCC buildings with Flat slab &Conventional slab (G+9,G+15
& G+23 Storey) having Rectangle, Hexagonal, Octagonal geometry, by
STAAD.pro V8i using Limit State Design method considering earthquake Zone III
as per the Indian Standard code of practice IS 1893-2002 part-I: Criteria for
Earthquake resistant structure.

 

Ø  To
model different structures with aforementioned configuration and compare them
using design aids like STAAD.pro V8i.

 

Ø  To
compare the seismic behavior of multi storied RCC building with Flat slab &
Conventional slab for different earthquake intensities in terms of various
responses such as, Beam Shear, Beam Moments, Maximum Nodal Deflection and
Maximum Axial load on Columns.

 

Ø  To
find the relationship between earthquake intensities and responses.

 

Ø  To
find the best slab system for high rise buildings in different geometries.

 

Author: