International Journal of Engineering Trends and Technology (IJETT) – Volume 28 Number 7 - October 2015
Analysis of Earthquake Resistant Properties of RC Core Steel
Composite Columns & RCC Sections Using Finite Element Analysis
Shahanaj P Hussan1, Anooja Bashir2
1
M-Tech student, Department of Civil Engineering, Ilahia College of Engineering and Technology, Mulavoor, Muvattupuzha,
Ernakulam, Kerala, India
2
Asst.Professor, Department of Civil Engineering, Ilahia College of Engineering and Technology, Mulavoor, Muvattupuzha,
Ernakulam, Kerala, India
Abstract — This study focuses on earthquake
resistant properties of RCC core steel composite columns of
different sections and conventional concrete column. A model
is proposed using ANSYS with proper boundary conditions.
The model is for RCC sections, core steel circular sections,
core steel I-section, core steel channel sections and column
with steel tube covering. The all composite materials are of
same cross sections. Values of deflections from the modal
analysis (in case of static) it is evident that using composite
column sections is better than RCC columns. These core steel
composite column types help in improve the ductile nature of
the column when compared to the conventional reinforced
concrete column. Encased core steel is useful for resisting
large axial compressive force and little bending moment, and
for preventing columns from shear failure.
The purpose of this study to describe the elastic
plastic behaviour of the core steel composite columns under
large compressive axial load and earthquake horizontal load,
and to show the composite columns have large better
earthquake resistant performance than RCC columns. Max
deflection, von-mises stress and a strain are obtained for
different cases and are to be compared.
Keywords — RCC – Reinforced Cement Concrete
I. INTRODUCTION
During the past few decades, several composite steelconcrete structural systems have been used in the construction
of tall buildings. One such systems employs composite
column that consist of steel shape encased in concrete and
composite girders that use metal deck between the steel
section and concrete slab. This system combines the rigidity
and formability of reinforced concrete with the strength and
speed of construction associated with structural steel to
produce economic structures. The concrete used for encasing
structural steel section not only increases its strength and
stiffness, but also protects it from fire damages. As a result,
the use of such columns is on the rise in building construction
in addition to applications in marine structures.
A large number of reinforced concrete (RC) buildings
collapsed with storey failures by 1995 Hyogoken-Nanbu
earthquake in Japan. Especially RC columns at the corner post
on the failure storey collapsed in shear brittle under large
compressive axial forces generated by large horizontal and
vertical accelerations. In order to prevent happening brittle
shear failure of RC columns and occurring the storey failure
ISSN: 2231-5381
of building structures, it is necessary to make the ductility of
columns larger. It can be thought using core steel composite
columns is useful as one of the reinforcing RC columns. The
purpose of this study to describe the elastic plastic behaviour
of the core steel composite columns under large compressive
axial load and earthquake horizontal load, and to show the
composite columns have large better earthquake resistant
performance than RC columns.
II. FEATURES OF PROJECT
The project consists of finite element analysis of
conventional and composite concrete column. In order to find
out the reinforcement in column, the structural modelling was
done by STAAD Pro.V8i. The concrete mix used for all the
structural member is M25 and steel is Fe415. The load
combinations were taken to obtain the maximum design loads,
bending moment and shear forces. The reinforcement can be
found out from STAAD designing.
Here one conventional concrete column and three
composite concrete columns were modelled. The concrete
specimen wants to be modelled using ANSYS package.
1. The conventional column of 400mm x 400mm
with 3.2m height.
2. The conventional column with ISWB 250
section inside it.
3. The conventional column with 76.2mm diameter
circular core steel section inside it.
4. The conventional column with ISMC 300
channel section inside it.
III. STAAD MODELLING AND DESIGNING
Here, A ground plus four Storey RC office building is
considered.
Plan dimensions
: 12 m x 10 m
Location considered
: Zone-III
Soil Type considered
: Medium stiff Soil
Grade of concrete
: M25
Grade of steel considered
: Fe 415
Live load on roof
: 1.5 KN/m2
Live load on floors
: 3 KN/m2
Roof finish
: 1.0 KN/m2
Floor finish
: 0.5 KN/m2
Brick wall in both direction
: 200 mm thick
Beam size
: 200 x 200 mm
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International Journal of Engineering Trends and Technology (IJETT) – Volume 28 Number 7 - October 2015
Column size
: 400 x 400 mm
Density of concrete
: 25 KN/m3
Density of brick wall including plaster : 20 KN/m3
Thickness of slab
: 150mm.
The load combinations are taken as per IS: 456-2000,
IS: 1893-2002 and IS: 13920
IV. FINITE ELEMENT MODELLING
ANSYS software has been used for conducting the finite
element analysis of conventional and composite column. Both
ends of the column were fixed. The concrete was modelled
using Solid65 element. The reinforcement was modelled using
beam188 element. The composite materials are modelled with
Solid 185 element. Here in this project mapped meshing is
used for the models.
A. Material Specifications
Steel
Young’s Modulus,
Poison’s ratio,
Density,
E
μ
ρ
= 2e5 MPa
= 0.3
=7850 kg/m3
Concrete
Young’s Modulus,
Poison’s ratio,
Density,
E
μ
ρ
= 2.5e4 MPa
= 0.15
=2414 kg/m3
TABLE 1
SPECIMEN DETAILS
Fig. 1 3D rendered view of G+4 building
By designing the required building in STADD, the column
have 8 numbers of 20mm diameter bars and 12mm diameter 2
legged stirrups are provided and as the shear reinforcement at
150mm spacing. Lateral ties are providing 12mm diameter at
300mm spacing.
Description
R.C.C
Column
Circular
Section
Column
Column
Size (mm)
400 x
400
Length
(mm)
Reinforcem
ent (mm)
Core Steel
(mm)
Axial
Load(KN)
Core
Steel
Channel
Section
Column
400 x
400
Rectang
ular
steel
tube
400 x
400
Core
Steel
ISection
Column
400 x
400
3200
3200
3200
3200
3200
8 No
20mm
-
8 No
20mm
76.2m
m Dia
8 No
20mm
ISWB
250
8 No
20mm
ISMC
300
1400
1400
1400
1400
8 No
20mm
3mm
thick
steel
section
1400
B. Modelling and Meshing
Fig.2 Details of column
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Fig.3 Modelling and Meshing of Conventional column
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400 x
400
International Journal of Engineering Trends and Technology (IJETT) – Volume 28 Number 7 - October 2015
Fig.8 Boundary condition and loading
Fig.4 Modelling and Meshing of column with I-section inside
V. ANALYSIS OF STRUCTURE
Fig.5 Modelling and Meshing of column with Circular core steel inside
It includes Static analysis, Modal analysis and finally
Response spectrum analysis.
Static analysis means that, it accounts only static cases.
That means at the time of time varying loads occur, the static
analysis avoids the inertia and effects due to damping. In this
analysis, it is used to determine the displacements of the
structure. And also, it determines the stresses and strains in the
structure.
Modal analysis means that, it simply find out the natural
frequencies and mode shape of the structures. When the
machine components were designed, the modal analysis is
used to find out the vibration characteristics also. The final
results of modal analysis are very important at the initial stage
of response spectrum analysis.
Spectrum analysis, it is the most important analysis used
in the earthquake analysis. Here, the final results of modal
analysis are used at the initial stage of spectrum analysis for
the calculation of stresses and displacements of the modal.
This stresses and displacements are used to determine the
response of structures at varying loading conditions like
earthquake, wave effects from sea etc.
According to the results of static and modal
analysis, the response spectrum analysis was carried out. The
input of response spectrum is get from static and modal
analysis. Earthquake resistant properties of the modals are
getting from the response spectrum analysis.
A. Design Spectrum
Fig.6 Modelling and Meshing of column with Channel section inside
C. Boundary Condition and Loading
Here, In ANSYS fixed support at bottom and hinged
support at top of the column. The axial load 1400kN is get
from STAAD is applied in the column axially.
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For the purpose of determining seismic forces, the
country is classified into four seismic zones. The design
horizontal seismic coefficient Ah for a structure shall be
determined by the following expression:
Ah
=
Provided that for any structure with T<= 0.1s, the value of
Ah will not be taken less than Z/2 whatever be the value of I/R
Where,
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International Journal of Engineering Trends and Technology (IJETT) – Volume 28 Number 7 - October 2015
Z = Zone factor
I = Importance factor
R = Response reduction factor
Sa/g = Average response acceleration coefficient
TABLE 2
Zone Factor, Z
Seismic zone
II
III
IV
V
Seismic
intensity
Low
Moderate
Severe
Very
severe
Zone factor, Z
0.10
0.16
0.24
0.36
Fig.9 Deflection of conventional column
For finding average response acceleration coefficient,
For rocky or hard soil sites
Sa/g
= 1+1.5T;
0.00 ≤ T ≤ 0.10
= 2.50
0.10 ≤ T ≤ 0.40
= 1.00/T 0.40 ≤ T ≤ 4.00
For medium soil sites
Sa/g
= 1+1.5T;
0.00 ≤ T ≤ 0.10
= 2.50
0.10 ≤ T ≤ 0.55
Fig.10 Von-mises stress of conventional column
= 1.36/T 0.55 ≤ T ≤ 4.00
For soft soil sites
Sa/g
= 1+1.5T;
0.00 ≤ T ≤ 0.10
= 2.50
0.10 ≤ T ≤ 0.67
= 1.67/T 0.67 ≤ T ≤ 4.00
In this work, using zone factor as 3, ie; seismic
intensity is moderate and the value of Z is 0.16, importance
factor = 1, response reduction factor = 3. The value of time
period, T is taken from graph, spectral acceleration Vs time
period. The Sa/g value is obtained as per time period. The
value of design horizontal seismic coefficient, Ah is done by
these values. The spectral acceleration value is obtained by Ah
x g, where, g = acceleration due to gravity. Frequency table
values are obtained from the time period value T and also we
know the spectral values. Thus, we can perform the spectrum
analysis.
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Fig.11 Deflection of I-section inside
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International Journal of Engineering Trends and Technology (IJETT) – Volume 28 Number 7 - October 2015
Fig.15 Deflection of Channel section inside
Fig.12 Von-mises stress of I-section inside
Fig.16 Von-mises stress of Channel section inside
Fig.13 Deflection of circular core steel inside
VI. RESULTS AND DISCUSSIONS
Explicit response spectrum analysis was conducted
on RCC conventional column and several composite column
models using ANSYS 14.5 for investigating the earthquake
resistance properties of columns under large compressive
axial loads and earthquake horizontal loads.
A. Numerical Results and Discussions from ANSYS Analysis
TABLE.3
Response Spectrum Analysis Result of Deflection and Von-Mises Stress
Fig.14 Von-mises stress of circular core steel inside
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Specimen
Convent
ional
column
Circular
core
steel
inside
Channel
section
inside
I-section
inside
Length
(m)
3.2
3.2
3.2
3.2
Deflection
(mm)
0.0595
0.00239
0.00311
Von-mises
stress
(N/mm2)
0.637
0.134
0.159
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0.00331
0.1669
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International Journal of Engineering Trends and Technology (IJETT) – Volume 28 Number 7 - October 2015
columns. Analysis is been carried out using ANSYS14.5.
Modelling and analysis criteria were validated using available
results in literature.
B. Conclusions
a) An analytical study reveals that, the introducing
composite action in column influences the load
carrying capacity of column significantly. The
selection in geometry of composite section is one of
the important factors. Its greatly influences the static
deformation characteristics of the column structure.
b) From Response spectrum analysis, the deformation is
greater at conventional column and lesser at column
having channel section inside.
c) Maximum stress concentration is occurring at
conventional column. And minimum stress
concentration is occurring at column having channel
section inside.
Fig.17 Deflection chart for Response spectrum analysis
Fig.18 Von-mises chart for Response spectrum analysis
VII. SUMMARY AND CONCLUSIONS
A. Summary
The RCC conventional and composite columns were
analysed using response spectrum analysis. 4 basic models
were created, one is conventional and the remaining are
composite columns. The whole models are used for analysis.
Analytical method was used to evaluate and compare the
earthquake resistant properties of conventional and composite
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ACKNOWLEDGMENT
I wish to thank the Management, Principal, and Head of Civil
Engineering Department of Ilahia college of engineering and
technology, affiliated by Mahatma Gandhi University for their
support. This paper is based on the work carried out by me
(Shahanaj P Hussan), as part of my PG course. The fruitful
interactions held with Mrs. Anooja Bashir during my project
are duly acknowledged.
REFERENCES
[1] Hasan Abdulhadi Ajel, Abdulnasser M Abbas “Experimental and
Analytical Investigations of Composite Stub Columns” Vol. 4, Issue 2,
February 2015.
[2] Rahel H. Khizer, B.R.Narayana, N.S.Kumar, “Numerical modeling of
concrete composite steel tubes” Volume: 03 Special Issue: 06 | May-2014 |
RRDCE
–
2014.
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