Buckling Analysis of RC Framed Structures with and without Bracings

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 04 Issue: 10 | Oct -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 607
Buckling Analysis of RC Framed Structures With and Without Bracings
Sudha S Goudar1 , R.G.Talasadar2
1PG Student department of Civil engineering, B.L.D.E.A’s V.P. Dr P.G. Halakatti College of Engineering and
Technology, Vijayapur.
2Associate Professor department of Civil engineering, B.L.D.E.A’s V.P. Dr P.G. Halakatti College of Engineering and
Technology, Vijayapur.karnataka, India
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Abstract - In general, concrete braced reinforced concrete
frame is one of the structural systems used to resist buckling
loads and buckling of multi-storey structures. The use of
concrete bracing systems for strengthening buckling
inadequate reinforced concrete frames is a viable solution for
enhancing buckling resistance. Concrete and steel is
economical, easy to erect and flexible to designformeetingthe
required strength and stiffness. A numerical method for the
solution of the elastic stability of fixed frames is presentedand
the procedure to perform elastic bucklinganalysisforframein
use computing buckling loads and buckling modes in frames
with fixed columns.
In this study buckling analysis of reinforced concrete building
with different types of bracings V, inverted V, X, Diagonal and
K type, bare frame, P-Delta effect, slenderness ratio, andshear
walls studied. The method is illustrated in detail for different
cases of single storey, three storey, five storey and ten storey
buildings is analysed for buckling using ETABS, one and three
storeys buildings is analysed for buckling using ANSYS
software. Comparing the both software’s values, the bracing
system improves not only the stiffness capacity but also the
buckling of the structure. Themainparametersconsideredare
buckling factor, p-delta effect, slenderness ratio and shear
wall.
Key Words: Buckling analysis of the structure using
ETABS and ANSYS, performance of slenderness ratio,
shear wall, P-delta, stiffness, Bracings.
1. INTRODUCTION
Buckling concept of restrained braces was first introduced
by Wakabayashi in 1973. Buckling can be defined as The
basic concept of critical buckling load Pcr the structure
encounters sudden failure when subjected to compressive
load and its length requests of size are greater than both of
its separate measurements such a column is known as a
section. we can see there are 2 types of the frames regard to
side sway where side sway prevented and frames with side
sway permitted. In first type of the frame The bucklingtakes
place when the applied load P is equal to critical Pcr
columns, and at the top end column is flexibly limited by
beam to which the column is firmly associated, and the
critical load of the section depends not only on the column
stiffness, additionally depend on rigidity of the beam.
1.1 Bracings
Different Story’s are selected like one-storey, three-storey,
five-storey and Ten-storey three bays frames was chosen
and five different bracing patterns and locations were
selected. Frame was modelled at Bay widthas4mandstorey
height as 3.5m. Bracing patterns include single Diagonal,
double diagonal (X), Chevron inverted V, K and V bracings.
1.2 Shear wall
For resistance of the earthquake forces shear wall frames
and concrete braced frames structural systems used.
Generally ReinforcedConcreteshear wallshavebeenusedas
main lateral load opposing framework in medium & tall
structures on account of their high lateral unbending nature.
1.3 Slenderness ratio
Slenderness ratio is the proportion length of a column and
minimum range of gyration of its cross area shaped by a
plane. If the slenderness ratio is smaller than (kl/r) min
failure happens by crushing. If the slenderness proportionis
more than (kl/r) min failure happens by buckling,deflection
load or stress diminishing for more slenderness.
1.4 P-Delta
They are second order impacts which increases raise the
deformations, member's method for movement and extend
the effective fundamental period of the structure. P-delta
effects in structure may be restrainedbyincreasingitssidely
rigidity, increasing its strengthorbycombiningofthosetwo.
2. MODELLING
When considering the presents study, an attempt is made to
quantify the influence of Buckling analysis of RC framed
structureWith bracingand Without bracing. and itspossible
to strengthen using shear wall, slenderness ratio, P-Delta
effect and stiffness. For this purpose typical 1,3, 5 and 10
storey structures are modelled & analysed using ETABS and
ANSYS software.

Table -1: Structural details of the model
Number of storey 1,3,5 and 10
Storey height 3.5m
Number of Bays 3 bays in both
directions
Spacing of Bays 4 m in both direction
Beam Size 230x450 mm
Column size 500x500 mm
Bracing size 300x300 mm
Grade of Materials M25 and Fe 500
Slab Thickness 150mm
Load Considered (Deadload
+ Floor finish + Live load )
8.2 kN/m2
2.1 Using ETABS Software
The bare frame models considered are described as
following
Fig-1 Shows models of Regular building without bracing 1,
3, 5 and 10 storeys structures.
Fig-2 Shows models of Regular building with bracing 1, 3,
5 and 10 storeys structures, and 3D model of shear wall.
The analysis is carried out for the bare frame as well as for
the braced frames by considering X, V , K, Diagonal,Inverted
V type bracing, slenderness ratio, shear wall, Stiffness and p
delta effect for the same model configuration described
above. The regular building elevation views with different
types of bracings are shown.
2.2 By using ANSYS
Fig-3 Bare model, Diagonal, K type bracing models using
Finite element method by using ANSYS Software.
Similarly models are prepared for the 1, 3, 5 storeys and 10
storeys. A finite element buckling study determines the
lowest buckling factors and their corresponding buckling
modes.
The bare frame models of 5 different configurations such
as Regular, one, three, five and ten are analyzed. Later X, V,
Diagonal, V, Inverted V and K bracings are applied to
strengthen the structures. The results are compared for
structures with and without bracingsfor3storeysstructures
of all models. The results are basically compared to find
which type of bracing will be more effective for different
regular structures.
 Buckling Analysis of frames
Analytic buckling studies identify additional classes of
instability besides Euler buckling. They include lateral
buckling, torsion buckling, and other buckling modes. A
finite element bucklingstudy determinesthelowestbuckling
factors and their corresponding modes.A buckling, or
stability, analysis is an Eigen problem. The size of the scalar
Eigen value is known as the “buckling load factor”. The
processed displacement Eigen vector is referred to as the
"buckling mode" or mode shape.
The results of analysis compared include P-delta,
slenderness ratio, Stiffness and Buckling of the structures
with bracing and without bracings.

Fig-4 3D models of buckling modes (first buckling modes
of models with bracing and without bracings)
Similarly buckling modes for diagonal,X,K,InvertedVtypeof
bracings for different stories.
2.3 Buckling modes of3storeystructuresbyusingANSYS
Fig-5 first buckling modes of 3 storey structures
Table-2 Variations of buckling modes values for 3 stroreys
structures.
Bare
model
X Diagonal K
61.888 327.27 206.96 347.24
Results of the buckling analysis were compared between the
ETABS and ANSYS the variations of buckling factor for bare
model 38%, X bracing 22%, K bracing 17% and diagonal
bracing 39%. The average difference betweenbothsoftware
values is 25%.
Similarly the buckling factor results are calculated for one,
five and ten storey by using ETABS and buckling factor is
calculated for one and three storey using ANSYS.
2.4Graphical representation of buckling factor values
Storey 3
0
50
100
150
200
250
1 2 3 4 5 6
Modes
Bucklingfactor
Fig- 6 Buckling modes v/s Buckling factor
Table-3 Buckling factor values for storey 3
Buckling
mode
1 2 3 4 5
Storey 3 26.686 38.557 79.223 160.2 175.06
The columns sizes for three storey structures considered
C300x300. The above graphs shows variations of buckling
factor for different modes. Number of stories increases the
buckling factor goes on decreases.
storey 3
0
200
400
600
800
1000
1200
Bare frame diagonal v bracing x bracing inverted v
bracing
bucklingfactor
C500x500
Fig-7 bracing v/s buckling factor.
Table-4 Variations of buckling modes values for 3 stroreys.
for different bracings by using ETABS software
Bare Inv V V X Diagonal K
100.753 942.67 369.979 421.508 726.077 286.075
Type of bracing system as lateral load resisting system,
material of bracing system also increases the stiffness and
ductility of the structure. Bracing system is good practice of
scheme for high rise RCC structures to strengthen against
buckling. So it can be concluded that Inverted V bracing
system is good practice for implementation in high rise
structures and reduces the damages in RCC structures
during lateral load resisting capacity of the structures.
Mode 1
0
500
1000
1500
2000
2500
Storey 1 Storey 3 Storey 5 Storey 10
Num ber of Stories
BucklingFactor
Without shear w all
With shear w all
Fig-8 comparison of without shear walls and with shear
walls for different stories.
Table-5 buckling modes values for 3 stroreys without
shear wall and with shear wall.
Buckling
mode
Without
Shear wall
With shear wall
1 100.753 580.709

As per analysis, it is concluded that buckling factor for three
storey building with shear wall is 82% more as compared to
R.C.C. building Without Shear Wall.
Mode 1
0
50
100
150
200
250
300
350
400
450
500
Number of stories
BucklingFactor
Membrane
Shell
Fig-9 Comparison of membrane and shell
Table-6 Buckling factor values for membrane and shell
Buckling Factor
Membrane 100.753 197.817 360.656 559.848
Shell 123.556 218.873 402.887 627.082
Load which is applied to the membrane objects transfers
directly to supporting structural objects, whereas meshed
shell objects have bending stiffness and therefore resist a
portion of the load through flexural deformation. Asa result,
less load will be available to transfer to beams locatedunder
a shell, while 100% of the load will transfer through a
membrane.
Storey 3
0
20
40
60
80
100
120
140
20 13.33 10 8
Slenderness ratio
Buckling
Fig-10 Slenderness ratio v/s buckling factor.
Table-6 Slenderness values and buckling factor values
Storey 3
Slenderness
Ratio Buckling
C200X200 20 5.962
C300X300 13.33 26.686
C400X400 10 62.475
C500X500 8 100.753
From the above mentioned graph it can be observed that
slenderness ratio (L/D) ratio is less. The deflection rate
considerably increases when L/D ratio is more.
Mode 1
0
50
100
150
200
250
300
350
400
450
Number of stories
BucklingFactor
bare frame
P-delta effect
Fig-11 Comparison of bare frame v/s p-delta effect.
Table-7 buckling factor values of p-delta effect
Storey 3
Buckling mode Bare frame P-Delta effect
1 100.753 61.475
One, three, five and 10 storey buildings were analysed with
P-delta effect and bare models. The buckling factor of the
building with P-delta effect and bare model that were
compared from the result shows that the buckling factor for
3 storey 40% less than without P-delta effect.Hence building
with P-delta effect resists the load effectively.
3. CONCLUSIONS
From the comparative study of various parameters, it is
observed that the building with bracingsdemonstratebetter
performance over the building without bracings
The following conclusion has been drawn based on the
results obtained from the present study.
 Storey forces are reduced inthebuildingframewith
bracings, which gives the stability of the building.
Subsequently the use of bracings is viewed as more
secure than the without bracings in the building.
 by Comparing the buckling factor valuesfora frame
with and without bracing, the buckling factor of
building increases using bracings like K type by
65%, V type 73%, X bracing 76%, diagonal 86%,
and Inverted V by 89%. So Inverted V type of
bracing have more buckling factor.
 The maximum buckling factor is observed incaseof
Inverted V bracing model for all i.e. 1, 3, 5, and 10
stories building frames.
 Slenderness ratio of thecolumnplay veryimportant
role in buckling analysis of the RC buildings. From
the results observed that, as theslendernessratioof
the column increases the buckling factor will
decrease as there will be a minimum bucklingfactor
even on maximum load.
 Buckling factor values for a frame is better when
slab is considered asshell insteadofmembrane.The
Variations betweenbuckling factorvaluesforstorey
one is 12%, storey three it is 18%, for five storeys
21 % and for ten storeys it is 23%. From the results

observed that shell model will give more bulking
factor for the frame.
 1,3,5, & 10 stories buildings wereanalyzed withand
without P-delta effect for bare models. From the
results it shows that the buckling factor for 1 storey
is 47%, for 3 storey 40%, 5 storey 36% and for 10
storey it is 34% less than without P-delta effect.
Hence building with P-delta effect resists the load
more effectively.
 From the results, it is concludedthatbucklingfactor
for the building with shear wall is more as
compared to R.C.C. building Without Shear Wall.
 Results of the simulations were compared between
the ETABS and ANSYS, the variations of buckling
factor value are 0-25%.
 From the results, adding bracings totheRCmoment
resisting frame, it will increase strength and
stiffness to the structure.
FUTURE SCOPE
 It is concluded that as per the analysis with the help
of ANSYS software it can used to develop five and
ten storey modelswithbracingandwithoutbracing.
 And models like V and Inverted V bracings can also
be prepared.
REFERENCES
 Nazim Abdul Nariman,MohammedA.Msekh(2013)
“Finite Element Analysis of the Buckling Critical
Loads in Un-Braced Steel Frames with Multiple
Slenderness Ratio Configurations”. (IJCSER) Vol. 1,
Issue 1, pp: (1-13), Month: October 2013-March
2014,
 Shadiya.K.P 1, Anjusha.R (2015) “Bracing
Configurations Effect on Buckling Restrained
Braced Frames”. International Journal ofInnovative
Research in Science, Engineering and Technology
(An ISO 3297: 2007 Certified Organization) Vol. 4,
Issue 4, April 2015.
 Z. Qu, Y. Maida, H. Sakata & A. Wada (2012)
“Numerical Assessment of Seismic Performance of
Continuously Buckling Restrained Braced RC
Frames”. Tokyo Institute of Technology, Japan
15WCEE LISBOA 2012.
 Timoshenko S.P. and Gere, J.M: Theory of Elastic
Stability, McGraw Hill Kogakusha Ltd., New York.
 Ratnesh Kumar, K.C.Biswal (2014)“Seismic analysis
of braced steel frames”. National institute of
technology rourkela, Orissa India May - 2014.
 Viswanath K.G et.al. (2010), Seismic Analysis of
Steel Braced Reinforced Concrete Frames,
International Journal of Civil and Structural
Engineering, 1(1), pp 114-116.
 W. N. Deulkar, C. D. Modhera and H. S. Patil,
”Buckling Restrained Braces for vibrationcontrol of
building structure”, International Journal of
Research and Reviews in Applied Sciences,
September 2010, 4(4).
 Neuss C. – Maisson B., (1984): “Analysis for P-Δ
effects in Seismic Response of Buildings”.Computer
and Structures, Vol. 19, No 3.
 Kulkarni J.G., Kore P. N., S. B. Tanawade, “Analysisof
Multi-storey Building Frames Subjected to Gravity
and Seismic LoadswithVaryingInertia”ISSN:2277-
3754, International Journal of Engineering and
Innovative Technology (IJEIT) Volume 2, Issue 10,
April 2013.
 Carlos Couto, Paulo Vila Real, Nuno Lopes, Joao
Paulo Rodrigueson“Bucklinganalysisofbracedand
unbraced steel frames exposed to fire”.Engineering
Structures, ASCE, 2013.
 G. Brandonisio, et al., "Seismic design of concentric
braced Frames," Journal of Constructional Steel
Research, vol. 78, pp. 22-37, 11// 2012.
 Londhe R.S. and Chavan. A. P. (2010). “Behavior of
building frames with steel plate shear wall”. Asian
Journal of Civil Engineering (building and housing)
vol. 11, 2010.

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