International Journal of Civil Engineering and Technology (IJCIET)
Volume 10, Issue 1, January 2019, pp.342–355, Article ID: IJCIET_10_01_032
Available online at http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=1
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
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ASSESMENT OF SEISMIC PERFORMANCE FOR
G+5 MULTI-STOREY BUILDING WITH
BRACINGS AT DIFFERENT STORIES
T.S.D. Phanindranath
Research Scholar, Department of Civil Engineering,
GITAM University, Visakhapatnam, Andhra Pradesh, India
Assistant Professor (c) University College of Engineering Vizianagaram (JNTU-K UCEV)
Vizianagaram, Andhra Pradesh, India
Balaji K.V.G.D
Professor, Department of Civil Engineering,
GITAM University, Visakhapatnam, Andhra Pradesh, India
PoleswaraRao, Kovela
Research Scholar, Department of Civil Engineering,
GITAM University, Visakhapatnam, Andhra Pradesh, India
ABSTRACT
The main aim of this paper is to identify the type of bracing for the better seismic
performance of the structure by building
steel bracings at different floor
levels.Duringearthquakes the human loss is mainly due to the failure of structures.
Seismic deficitstructures will crumble even at low magnitude earthquakes.Many
existing structures need to be retrofitted,installation of steel bracing for existing
structure will be easiest way instead of buildingshear walls.Steel tubular X-bracing
system have been installed to the strcuture at different floor levels for choosen G+5
RCC building and analyzed by Non-linear static push over analysis.Six cases are
considered in this study, in each case the placement of bracing were changed to find
out the better performane of the structue with variation in the placement of bracings at
different storey levels.The comparisions made between these six cases by keeping base
model as ideal model along with the parameters like base shear,displacement and
inter-storey drift.After comparing it was found that there is a significant increase of
Base Shear by 14.90%,16.53% for case-3,case-5 models respectively when compared
with basemodel i.e. case-1with out bracing. The displacement is reduced by 17.39%,
17.39% for case-3 and case-5models respectively when compared with base model.
There is a reduction of inter-storey drift by 33.33%, 33.33% for case-3 and case-5
models respectively when compared with base model. Case-3 and case-5 braced
frames has been significantly performed well with the reduction in storey drifts and
displacements and increase in base shear.
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Assesment of Seismic Performance for G+5 Multi-Storey Building with Bracings at different Stories
Keywords: Push Over Analysis, Bracings, Sesimic Performance of Multistorey
Building,Placement of Bracings,Base Shear,Displacement,Storey Drift, Storey Level.
Cite this Article: T.S.D. Phanindranath, Balaji K.V.G.D, PoleswaraRao and Kovela,
Assesment of Seismic Performance for G+5 Multi-Storey Building with Bracings at
different Stories, International Journal of Civil Engineering and Technology (IJCIET),
10 (1), 2019, pp. 342–355.
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1. INTRODUCTION
1.1. General
Structure may experience sesimic forces occasionaly during its life time.When an existing
structure is designed only for gravity loads or incapable of resisting the lateral loads induced
due to earth quake loads, it should be able towithstand seismic loads without any structural
damage.The implementation of earthquake design is important in high seismic zones and
evenfor tall structures in low sesimic zones.To avoid human and property loss the structure
should be checkedas per the revised seismic code. Various lateral load resisting systems are
available even for existing structures The behaviours of structure under seismic load is studied
to select theconfiguration of resisting system.It is important to know the behaviour of
structure due to sesimic loads and finding out the type of resisting system and configuration
of resisting system.The major common problem in the structure is lateral stability especially
with5 or 6 stories structures.Displacement is aconcern parameter in the tall structures which
disturbs the structure and increases the chance of major failure in structural elements.If the
same structure experiences consecutive earthquakes there might be a chance of failure of the
structure, due to the execssive deflections in weak structural elements.
The columns of RCC structure will resist lateral loads, including wind and seismic loads.
Steel moment frames like bracings will improve resistance capacity of lateral loads through
flexural strength of members. Bracing members will resist lateral loads by transferring axial
forces both compression and tension through diagonal bracing members.These bracings will
transfer loads from roof or floor diaphragms through shear connections and to foundation A
few common configurations are cross bracings, chevron bracing, V-bracing, single diagonal
bracing, double diagonal bracing etc.
The configuration of bracings in a structure may show the variation in the resistance
criteria.Due to the changes in the placement of bracings, base shearand inter-storey driftwill
exhibit considerable varaition.So the placement of bracings will also play a crucial role in the
determination of results.
As the name indicates Push over analysis pushes the structure unitl the maxiumum
capacity of the building is reached.In case of earthquake loads this analysis leads to the
determination of deformation and cracking of the structure.The formation of plastic hinges
can also be studied which throw light on the failure pattern of the structure. Push over
analysis is an approximate tool to understand the building performance under non linear static
analysis and gets the capacity of the building for maximum displacement.
Various research papers are availble in the scope of this work Hendramawat A Safariki
et.al[3]evaluated the improvement of sesimic performance for RCC existing structure with
the installation of steel bracing.In this work three methods are adopted for the seismic
evaluation,Nonlinear static push over displacement coefficient method as explained in FEMA
356, Nonlinear static pushover displacement coefficient method as described in FEMA440
and dynamic time history analysis following indonesian code of seismic resistance building
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T.S.D. Phanindranath, Balaji K.V.G.D, PoleswaraRao and Kovela
criteria.The displacement determined from non linear push over analysis of the existing
building is 0.188m in X-direction and 0.132m in Y–direction.The performance of the existing
building could be improved by introducing steel bracings.Displacements are reduced by 16%
–55% if the proposed steel braces are used.MagudeaswaranPalanisamy et.al[7] concluded
that steel structures will have more advantages when compared with RCC structures because
of its cost efficient, sustainable, durable, ductile and safe. To analyze dynamic behavior of the
structure due to dynamic loads non–linear behavior of the structure is to be considered. The
non-linear performance of the structure can be determined by push over analysis. In this work
the push over analysis is carried out to two frames namely bare frame and steel frame using
Ansys software under lateral loading and it is validated experimentally. Yield load and
ultimate load for steel braced frame is greater and deflection for steel braced is less when
compared with bare frame due to increase its diagonal stiffness of the frame.
DhangarLaxmiBalappa et.al [2] concluded that the buildings may collapse in the event of
earthquake even if they appear strong enough. The building collapsed in the bhuj earthquake
is seismic deficient structure, which is not constructed in the favor of seismic code. To
determine the performance of framed buildings under expected earth quakes a non-linear
static push over analysis has been conducted. In this work 4 models of G+10 has been
prepared with and without bracings and analyzed in SAP 2000 software. The results
compared in terms of base shear, displacements, time period, location of hinges and push over
curves obtained from the study shown the improved performance of the braced structure when
compared with bared structure. Prince kaley et.al [9] determined the seismic performance of
multi storied building according to IS 800-2007.By introducing steel bracing system to the
structure the ductility of the structure can be increased. Different types of bracings like X, V,
Inv-V, diagonally braced configurations have been introduced to structure.G+9 multistory
steel building has been modeled with and without bracings. By using SAP 2000 software
nonlinear static analysis (push over analysis) has been run for these models. Various
parameters like mode shapes, frequencies, mode shapes, deformed shapes, hinge results are
compared between braced and bare models to determine the relative performance of selected
models.
1.2. Objective of the work
The main objective of the study is to improve the resistance capacity of the structure in terms
ofbase shear, storey displacements and inter storey drifts by introducingsteel bracings to the
structure and aslo to identify the configuration of bracings in the strcuturewhich offers
maximun advantage with minimun number of bracing patterns.
1.3. Scope of the work
The scope of the work is shown by the following models.
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Assesment of Seismic Performance for G+5 Multi-Storey Building with Bracings at different Stories
Figure 1.1 With Out BracingFig-1.2 Bracings at Cellar level
Figure 1.3 Bracings at Cellar and 2nd Storey
Figure 1.5 Bracings at First and 4th Storey
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Figure 1.4 Bracings at First Storey
Figure 1.6 Bracings for Entire Structure
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In the first case no bracings are provided to the structure and it is taken as refernce for
comparision.In the second case bracings are erected only at cellar level,bracings are erected
for cellar and to second storey in the third case. In fourth case bracings are installed only at
first storey, and for fifth case bracings are installed at first and fourth storey, for the last model
i.e, sixth case bracings are erected to the whole structure.
2. STRUCTURE MODELLING
Dead loads, live loads and load combinations are assigned to the structure to generate required
models (6 cases) with same structural element specifications. Steel X-Bracing system with
tubular cross section is installed by varying storey levels as shown in the previous
figures.Non–linear static push over analysis has been run to all the 6 cases to determine the
capacity of the structure.
2.1. Material property
Table 2.1 properties of the material
Concrete grade
Steel grade
Compressive strength of concrete
Yeild strength of main reinforcement
Yeild strength of bracing members
Density of rcc
Density of steel
M25
Fe415
25 N/mm2
415 N/mm2
250 N/mm2
25 kN/ m3
7850 kg/m3
2.2. Member property
Table 2.2 properties of the structural elements
Slab thickness
Beam size
Column size
150 mm
230 mm x 450 mm
300 mm x 450 mm
2.3. Description of model
Table 2.3 Model description
Number of stories
Floor height
Buiding height
width of the bay in X-direction
width of the bay in Z-direction
Buidling area
Building type
Live load
Dead load of slab
Load for inner walls(4.5’’)
Load for external walls(9’’)
Dead load for beams in x-direction
Dead load for beams in y-direction
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G+5
3m
18m
5m x 4 bays=20m
4m x 8 bays =32m
640 m2
OMRF and SMRF (residential)
2kN/ m2
4 kN/ m2
5 kN/ m
6.8 kN/ m
2.60 kN/ m
2.60 kN/ m
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2.4. Modeling of Bracing Member
As per IS 15988.2013 [6] code specifications tubular section was adopted due to its high
moment of inertia and radius of gyration for same cross sectional areas while compared with
angular and channel sections.The ratio of end to end width of member to the wall thickness
should not exceed 288/√fy for tubular section [6]. Therefore depending upon the code
specifications the cross section has been adopted for tubular section.
Figure 2.1 Tubular Cross Section
2.5. Property of steel section
Table 2.4 Steel sectional properties
Weight per meter length (kg)
Area of cross section (mm2)
Moment of inertia (m4)
Modulus of section (m3)
Shear area (mm2)
Radius of gyration (mm)
4.09
505
1.227 x 10-7
6.130 x 10-6
300
15.6
3. RESULTS AND DISCUSSIONS
3.1. Base Shear
Table 2.5 Base shear for various cases
CASE
Case-1
Case-2
Case-3
Case-4
Case-5
Case-6
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BASE SHEAR (kN)
7221
7364
8297
7675
8415
9975
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Figure 3.1 Base Shear

For case-2 the Base Shear is increased by 2.00% when compared with case-1

For case-3 the Base Shear is increased by 14.90% when compared with case-1

For case-4the Base Shear is increased by 6.28% when compared with case-1

For case-5 the Base Shear is increased by 16.53% when compared with case-1

For case-6 the Base Shear is increased by 38.13% when compared with case-1
3.2. Displacement &Storey Drift
Case-1
Table 3.1. Displacement and Inter Storey Drift for Case-1
Storey Height (m)
Sixth floor
Fifth floor
Fourth floor
Third floor
Second floor
First floor
Ground floor
Plinth level
Displacement (mm)
Inter Storey Drift
(mm)
46
42
38
32
26
14
06
00
04
04
06
06
12
08
06
00
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Allowable Inter
Storey Drift
(mm)
(0.004xh)
12
12
12
12
12
12
12
12
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Assesment of Seismic Performance for G+5 Multi-Storey Building with Bracings at different Stories
Figure. 3.2. Displacement of Base Model
Case-2
Table 3.2. Displacement and Inter Storey Drift for Case-2
Storey Height (m)
Sixth floor
Fifth floor
Fourth floor
Third floor
Second floor
First floor
Ground floor
Plinth level
Displacement (mm)
Inter Storey Drift
(mm)
44
38
33
27
18
08
02
00
06
05
06
09
10
06
02
00
Allowable Inter
Storey Drift
(mm)
(0.004xh)
12
12
12
12
12
12
12
12
Figure3.3 Displacement of Case-2 Model
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T.S.D. Phanindranath, Balaji K.V.G.D, PoleswaraRao and Kovela
Case-3
Table 3.3 Displacement and Inter Storey Drift for Case-3
Storey Height (m)
Sixth floor
Fifth floor
Fourth floor
Third floor
Second floor
First floor
Ground floor
Plinth level
Displacement (mm)
Inter Storey Drift
(mm)
38
35
32
24
16
09
04
00
03
03
08
08
07
05
04
00
Allowable Inter
Storey Drift
(mm)
(0.004xh)
12
12
12
12
12
12
12
12
Figure 3.4 Displacement of Case-3 Model
Case-4
Table 3.4. Displacement and Inter Storey Drift for Case-4
Storey Height (m)
Sixth floor
Fifth floor
Fourth floor
Third floor
Second floor
First floor
Ground floor
Plinth level
Displacement (mm)
Inter Storey Drift
(mm)
41
38
33
28
18
10
05
00
03
05
05
10
08
05
05
00
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Allowable Inter
Storey Drift
(mm)
(0.004xh)
12
12
12
12
12
12
12
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Assesment of Seismic Performance for G+5 Multi-Storey Building with Bracings at different Stories
Figure 3.5 Displacement of Case-4 Model
Case-5
Table 3.5 Displacement and Inter Storey Drift for Case-5
Storey Height (m)
Sixth floor
Fifth floor
Fourth floor
Third floor
Second floor
First floor
Ground floor
Plinth level
Displacement (mm)
Inter Storey Drift
(mm)
39
37
30
27
20
12
06
00
02
07
03
07
08
06
06
00
Allowable Inter
Storey Drift
(mm)
(0.004xh)
12
12
12
12
12
12
12
12
Figure 3.6 Displacement of Case-5 Model
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Case-6
Table 3.6 Displacement and Inter Storey Drift for Case-6
Storey Height (m)
Sixth floor
Fifth floor
Fourth floor
Third floor
Second floor
First floor
Ground floor
Plinth level
Displacement (mm)
Inter Storey Drift
(mm)
30
28
24
21
18
12
06
00
02
04
03
03
06
06
06
00
Allowable Inter
Storey Drift
(mm)
(0.004xh)
12
12
12
12
12
12
12
12
Figure 3.7 Displacement of Case-6 Model
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Figure 3.8 Displacement for Various Cases at each storey level
Figure 3.9 Displacement for Various Cases at Top Storey

For case-2 the Displacement is reduced by 4.34% when compared with case-1

For case-3 the Displacement is reduced by 17.39% when compared with case-1

For case-4 the Displacement is reduced by 10.86% when compared with case-1

For case-5 the Displacement is reduced by 17.39% when compared with case-1

For case-6 the Displacement is increased by 34.78% when compared with case-1
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Figure 3.10 Inter Storey Drift for Various Cases
Figure 3.11 Maximum Inter Storey Drift in Each Case

For case-2 the Inter-Storey Drift is reduced by 16.66% when compared with case-1

For case-3 the Inter-Storey Drift is reduced by 33.33% when compared with case-1

For case-4 the Inter-Storey Drift is reduced by 16.66% when compared with case-1

For case-5 the Inter-Storey Drift is reduced by 33.33% when compared with case-1

For case-6 the Inter-Storey Drift is reduced by 50.00% when compared with case-1
CONCLUSIONS
Non-linear static analysis (push over analysis) has been run to compare the results between
models to find out the effective configuration of bracing system for selected cases. The base
model experiences high displacement and high inter-storey drift with less attraction of base
shear. By introducing X-configuration bracing system into the structure the selected
parameters like displacement, inter-storey drifts has been reduced with a considerable
increase of base shear.
There is an increase of Base Shear by 14.90% for case-3 when compared with base model
i.e. case-1.For case-5 the Base Shear is increased by 16.53% when compared with case-1.
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Assesment of Seismic Performance for G+5 Multi-Storey Building with Bracings at different Stories
The displacement is reduced for case-3 model by 17.39% when compared with case-1.The
displacement is reduced for case-5 model by 17.39% when compared with case-1.Inter storey
drift is reduced by 33.33% for case-3 model when compared with base model. For case-5 the
Inter-Storey Drift is reduced by 33.33 % when compared with case-1.Case -3 and case-5
braced frames has been significantly performed well with the reduction in storey drifts and
displacement percentage and increase in base shear.
Instead of installing bracing members along periphery of the model, finding out the
configuration of bracing members between the storey levels which results in allowing the
selected parameters up to permissible limits gives way to the reduction of quantity of braced
members. Finding out the alternate configuration of bracing members can also reduce
financial efforts. Determination of capacity of the structure and reducing the displacement,
storey drift and enhancing the base shear capacity which gives way in the safety of the
structure against dynamic loads by finding out the exact placement of bracing members in the
structure.
Case-3 and case5 models would be better alternative while resisting the earth quake loads
effectively with less number of bracings
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