Analysis of rc framed structures with central and partial openings in masonry infill wall using diagonal strut method

IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
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Volume: 04 Issue: 04 | Apr-2015, Available @ http://www.ijret.org 640
“ANALYSIS OF RC FRAMED STRUCTURES WITH CENTRAL AND
PARTIAL OPENINGS IN MASONRY INFILL WALL USING
DIAGONAL STRUT METHOD”
Chidananda HR1
, Raghu K2
, G Narayana3
1
Post graduate student, Dept of Civil Engineering, SJCIT, Chickballapura, Karnataka, India
2
Assistant professor, Dept of Civil Engineering, SJCIT, Chickballapura, Karnataka, India
3
Head of the department, Dept of Civil Engineering, SJCIT, Chickballapura, Karnataka, India
Abstract
In Reinforced concrete frames the masonry infill walls are a common practice in countries like India, where the region is prone to
seismic activity. In general, the masonry infill walls are treated as nonstructural element in structural analysis and only the
contribution of its mass for is considered and it’s structural parameters like strength and stiffness is generally ignored in practice,
such an approach may lead to an unsafe design. Infill walls resist lateral loads but because of the openings in the infill wall the
resistance may slightly reduce. The IS code provisions do not provide guidelines for the analysis and design of RC frames with
infill wall and for different percentage of openings. In this study, an office or residential building outer side central opening or
outer side partial openings are used and analysis is carried for Bare Frame model, infill walls without opening, infill walls with
outer periphery central opening and infill wall with outer periphery partial opening models. In ETABS software G+14 RC framed
building models has been prepared, Equivalent Static Lateral force method, Response spectrum method has been performed for
analysis as per IS 1893 : 2002 including p-delta effects. Storey displacement, Storey shear, Storey drift, with soft storey
considering the effects of infill wall with central and partial openings are the parameters considered in this study. For modeling,
the Equivalent diagonal strut method has been used to find out the width of Strut using FEMA 273 .The results for bare frame,
infill wall, and infill wall with central and partial openings are discussed and conclusions are made.
Keywords: Equivalent diagonal strut, stiffness, Drift limitation.
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1. INTRODUCTION
Earthquake is responsible for the ground motion in all
directions, inducing the inertial forces on the structures.
Thus the structure has to withstand lateral loads due to
earthquake, wind loads along with the gravity loads.
Nowadays RC frames are the common construction practice.
The gap created between the columns, beams are filled by
infill materials like bricks. Due to functional requirements
the openings are provided in wall for windows, doors etc.,
In RC buildings the gravity loads do not cause effect, but the
lateral loads like wind, earthquake tremors are a matter of
great concern and need special design consideration. These
lateral loads create critical stress in a building, causing
lateral sway and can reach a stage of causing discomfort for
the occupants.
The presence of infill walls increases the lateral stiffness,
strength and reduces the fundamental period. The presence
of openings in the infill walls can reduce some amount in
the increase of lateral stiffness due to infill wall.
The behavior of the infill walls subjected to the lateral loads
is represented as shown in fig 1. When the lateral loads are
applied the infill walls resists to some extent creating gaps at
the corners as shown.
If the openings provided in the infill walls are small, its
effect may be negligible in stiffness calculation. If the
openings are large, it may interfere the diagonal bracing
action (fig 2), thereby causing premature shear failure.
Fig -1: Behavior of the infill wall as a strut member.

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Fig -2: Bracing action of the infill wall
1.1 Types of Infill Provisions
Fig -3: Bare frame
Fig -4: Fully infilled frame
Fig -5: Infilled frame with central opening
Fig -6: Partially infilled frame
The infill walls are provided in different manner as shown in
Fig 3, 4, 5, 6.
2. LITERATURE REVIEW
Many Researchers have developed equations for calculating
the “Equivalent Diagonal Strut width”. Some of the major
are:
1. In 1961 Holmes,
W =
dz
3
where, dz = Diagonal length of infill panel
2. In 1962 Smith,
W = H L
2 2
α +α
h
h
α π 1
= .
L' 2 λ L'
panel
h.
p p
E .tsin2θ
λ L' = L'
4.E I .h
L
l.
α 1
= π.
L' λ L'
panel
L.
p b
E .tsin2θ
λ L' = L'
4.E I .L
3. In 1969 Smith and Carter,
W = 0.58    
h
-0.445
0.335dz x1
λ H'
H
 
 
 
where x=
0.064
1
H
 
 
 

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λh =
s
h s
4
Etsin2θ
4E IH
4. In 1971 Mainstone,
W = 0.175dz (λhH)-0.4
5. In 1984 Liaw and Kwan,
W =
h
(0.95Hcosθ)
λ H
6. In 1992 Paulay and Priestley,
W =
dz
4
7. In 2009 Chethan.K,
W = 1.414αh ,
h
π
α =
2λ
m
c c
4
E tsin2θ
λ =
4E I h
3. METHOD OF ANALYSIS OF THE INFILL
WALL
3.1 Data Taken
Storey G+14 (6X4 BAYS)
Typical storey height 3.5m
Beam size 400 X 500 mm
Column size 600 X 600 mm
Live load 3.5 KN/m2
Floor finish 0.6 KN/m2
Water proof on terrace load 1.5 KN/m2
Response reduction factor 5
Type of soil Medium
Damping factor 5%
Grade of concrete M30
Steel Fe500
Density of concrete 25 KN/m3
Density of brick infill 20 KN/m3
Poisson’s ratio of concrete 0.2
Poisson’s ratio of brick infill 0.15
Modulus of elasticity of
concrete
22360.67 KN/m2
Modulus of elasticity of brick
infill
4000 KN/m2
Thickness of slab 150 mm
Thickness of wall 230 mm
Seismic zone V
Wind speed 50 m/s
Terrain category 2
Structure class C
3.2 Types of Model
ID Description
BFGSS0% Bare frame with ground soft
storey without opening.
storey with 30% opening.
storey with 60% opening.
SFGSSC0% Strut frame with ground soft
storey without opening.
storey with 30% central
opening.
storey with 60% central
opening.
SFGSSP30% Strut frame with ground soft
storey with 30% partial
opening.
SFGSSP60% Strut frame with ground soft
storey with 60% partial
opening.
3.3 Modeling of Infill Wall
Fig -6: Plan view of the model

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Fig -7: Elevation view of Bare frame and Strut frame
3.4 FEMA Approach
In the case of an infill wall located in a lateral load resisting
frame the stiffness and strength contribution of the infill are
considered by modeling the infill as an equivalent
compression strut. Because of its simplicity, several
investigators have recommended the equivalent strut
concept. According to FEMA 273, infills are assumed as an
equivalent diagonal strut with pin joint at the corners as
shown Fig 8.
Fig -8: Equivalent diagonal strut for the infill panel
W=0.175 [λ’
h]-0.4
d’
Where, λ’
= 4 ( 2 ) / (4 ')EiTSin EfIcH
T= thickness of wall
Ei = Elasticity of concrete
Ef = Elasticity of brick infill
Fig -8: Reduction factor curve
Reduction factor = 1-2αw
0.54
+ αw
1.14
Opening Percentage (%) =
op
infill
Area of opening (A )
Area of the infill(A )
4. RESULT AND DISCUSSION
4.1 Displacement:
Table -1: Displacement in X direction
EQ RS Wind
BFGSS0% 62.5 48.8 30.8
BFGSS30% 59.8 41.7 30.6
BFGSS60% 55.8 38.9 30.6
SFGSSC0% 32.4 23.9 7.4
SFGSSC30% 34.6 24.9 8.7
SFGSSC60% 35.5 25.5 9.1
SFGSSP30% 33.4 24.2 7.9
SFGSSP60% 32.8 24.6 8.4
Table -2: Displacement in Y direction
EQ RS Wind
BFGSS0% 66.3 51.3 50.8
BFGSS30% 63.4 44.2 50.8
BFGSS60% 59.1 41 50.8
SFGSSC0% 37.6 27.7 13.8
SFGSSC30% 37.9 27.9 14.6
SFGSSC60% 38 28.3 14.8
SFGSSP30% 37.8 27.8 13.9
SFGSSP60% 37.9 27.9 14.2
The displacements values for different models as shown in
table 1 and table 2. The displacement is reduced by 51%
from the bare frame model to the infilled frame model. But
when we consider the infilled frame with central opening
and partial opening 40 – 45 % of the displacement is
reduced.

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4.2 Storey Drift:
Chart -1: storey drift in X direction
Chart -4: storey drift in Y direction

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The storey drift versus storey no is ploted for Equivalent
static method , response spectrum method. wind analysis as
shown in chart 1 to chart 6.The storey drift for the first
storey is higher because of the open ground storey. The drift
are within the limitation specified in IS 1893:2002.( ie.
0.004 times storey height)
4.3 Stiffness:
Chart -7: Stiffness in X direction
Chart -11: Stiffness in Y direction
Chart -12: Stiffness in Y direction

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The stiffness for different models as shown in Chart 7 to
Chart 12. The stiffness is increased by 68 % by considering
the effect of infill walls and about 10% reduction due to the
opening has been observed.
4.4 Time Period:
Table -3: Time period
The time period for different models is as shown in table 3.
The time period is found to be decreased by 46% from bare
frame model to infilled frame model. Because of the
presence of the opening the time period has slightly incresed
compared to infilled frame model.
5. CONCLUSION
In this paper bare frame , infilled frame models with and
without opening are prtepared for linear static analysis and
response spectrum analysis. The p-delta effect also been
analysed but the result showed a negligible amount of
variations, in that time period has significant changes. From
this analysis, it shows thast p-delta effect can be considered
for higher storey buildings. The displacement values shows
that there is a significant decrease in displacement by
considering the effect of infills and slight increase in
displacement due to openings.
The stiffness is increased by about 70% by considering the
effect of infills. The base shear was alson found to be
incresed. It can also be concluded that, the increase in
percentage of opening leads to decrease in the lateral
stiffness.
ACKNOWLEDGEMENTS
I am thankful to my guide Mr. Raghu K and Dr. G Narayana
for their guidance and also thankful to department civil
engineering S J C Institute of technology, chickaballapur.
Thanks to my dear friends who have supported me to
complete this work.
REFERENCES
[1].. “Analysis Of RC Frame With and Without Masonry
Infill Wall with Different stiffness with Outer Central
Opening” by Mohammad H. Jinya, V. R. Patel ,Volume: 03
Issue: 06, Jun-2014, http://www.ijret.org.
[2].. “Dynamic Analysis of Infills on R.C
FramedStructures” by Manju G, Volume 3, Issue 9,
September 2014, www.ijirset.com.
[3].. “Seismic Performance of Friction Pendulum Bearing by
Considering Storey Drift and Lateral Displacement” by
Vindhya Bhagavan, G.V Sowjanya, Chethan Kumar B,
Sandeep Kumar D.S, Volume: 03 Issue: 08 | Aug-
2014,www.ijret.org.
[4].. “The Influence of Infill Walls on RC Frames under
Seismic Excitation” by Lului,Ziyan Wu, November 2014,
volume 2, issue 4, http://www.ivypub.org.
[5].. “Influence of Masonry Infill Walls On Seismic
Performance of RC Framed Structures a Comparision of
AAC andConventional Brick Infill” by Vikas P. Jadhao,
Prakash S. Pajgade, Volume-2, Issue-4, April 2013, IJEAT.
[6].. “Earthquake Analysis of High Rise Building with and
Without In filled Walls” by Wakchaure M.R, Ped S. P,
Volume 2, Issue 2, August 2012, www.ijeit.org.
[7].. “Equivalent Strut Width for Partial Infilled Frames” by
Prachand Man Pradhan, DOI: 10.5923/j.jce.20120205.03,
Journal of Civil Engineering Research 2012, 2(5): 42-48.
[8].. “Seismic Analysis of RC Frame Structure with and
without Masonry InfillWalls” by Haroon RasheedTamboli
and Umesh.N.Karadi , Volume.3 / Issue 14/ October2012,
www.tnsroindia.org.in.
[9].. E-tabs version 2013 manual
[10].. IS1893 (part 1):2002 “Criteria for Earthquake
Resistant Design of Structures”- General Provisions and
Buildings (fifth revision).
[11].. IS 875 (part 3):1987 “Code of practice for design
loads (other than Earthquake loads) for Buildings and
Structures “- Wind loads (second revision).
[12].. Proposed Draft Provisions and Commentary on Indian
seismic code IS 1893 (part1) by Dr. Sudhir K Jain and Dr. C
V R Murthy – IITK-GSDMA-EQ15-V3.0.
BIOGRAPHIES
Chidananda H R is a M.tech Disseration
student doing his thesis under the
guidance of Mr. Raghu K from
Visveswaraya Technological University,
Belgaum
He is Mr. K Raghu Assistant Professor,
Department of civil engineering, S J C
Institute of Technology, Chickaballapur.
He is also a structural Design consultant.
He has more than 6 years of experience in
the field of structural and civil
engineering. He has more than 3 years of
teaching Experience. He has designed various projects
which includes steel structures and High rise buildings.

_______________________________________________________________________________________
He DR. G Narayana, Professor and
Head of Department, Department Of
Civil Engineering, S J C Institute of
Technology, Chickaballapur. He has a
wide experience in teaching and research
in the field of Structural engineering. He
is also a structural designed consultant for many projects.

Analysis of rc framed structures with central and partial openings in masonry infill wall using diagonal strut method

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