Dynamic Analysis of Outrigger Braced Systems in High …ijifr.com/pdfsave/19-08-2017140IJIFR-V5-E12-007.pdfhave been studied in detail and ... In this study The Analysis of the tall

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International Journal of Informative & Futuristic Research ISSN: 2347-1697

Volume 4 Issue 11 July 2017 www.ijifr.com

Abstract

Braced frame structures provide high stiffness and moderate ductility. By employing the braced frame system, the damage is more uniformly distributed over the height. However structures taller than 8-storey are prone to lateral drift amplification due to the higher mode effects. In this study, in order to control the lateral drift, it is proposed to add a set of outrigger trusses at various storey level and to locate the optimum location. Accordingly, in this study G+40 storey steel building is varied with double diagonal bracing and chevron bracing along with varying positioning of outrigger location, in a high risk seismic zone IV and soil type II. Response spectrum analyses conducted in ETABS software are considered in this study to analyze the behavior of the steel frame building with double diagonal bracings and chevron bracings with combination of outriggers at different storey levels in the G+40 storey building.

Dynamic Analysis of Outrigger Braced

Systems in High Rise Steel Building

Paper ID IJIFR/V4/ E12/ 007 Page No. 8521- 8537 Research Area Civil

Engineering

Key Words Bracings, Outrigger, Steel Structure, Tall Building, Earthquake Load,

ETABS

1st Sathyamurthy K.

P G Student,

Department of civil engineering,

Vijaya Vittala Institute of Technology,

Visvesvaraya Technological University ,

Karnataka, India

2nd Kavitha A. S.

Professor,

Department of civil engineering,

Vijaya Vittala Institute of Technology,

Visvesvaraya Technological University ,

Karnataka, India

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ISSN: 2347-1697

International Journal of Informative & Futuristic Research (IJIFR)

Volume - 4, Issue -11, July 2017

Continuous 47th Edition, Page No. : 8521- 8537

Dr. Gajanan L. Gulhane :: Correlative Study of Anxiety and Study Habits with Academic Achievement of Secondary Students

I. INTRODUCTION

People from rural areas are migrating to cities due to the Industrial Revolution, the

availability of jobs and facilities. Therefore metro cities are very densely populated.

Availability of land has decreased and the price of the land has increased. To solve this

problem the use of multistorey building is needed. However, such provisions only

increase the weight and live load of the structure along with earthquake forces. With an

increase in the amount of stress, strain, deformation and displacement in the structure

there is ultimately increases in the cost of construction due to the increased sectional

elements. Obviously, bare frames are to be more flexible and have great section

requirement to withstand the forces induced. The same can be minimized by making the

structure more rigid, but it appears to be not feasible and also uneconomical. The lateral

stability in the overall frame-work can be improved by using bracing systems. The

bracing members of such braced frame act as truss system to resist lateral forces and are

subjected primarily to axial stress in the elastic range. The efficiency of the braced frame

structure can be further more increased by introducing braced frames with outrigger

system.

To increase the strength and stiffness of steel frames and composite frames the use of

Steel bracing is comparatively effective. It reduces the forces caused by earthquake and

also makes the structure very good in absorbing energy. The structures will safely resist

forces and deformations due to severe ground motions which are good in energy

dissipation.

There are two types of Steel Bracing System such as,

a) Concentric bracing system.

b) Eccentric bracing system

Mentioned below are the bracing schemes for concentrically braced frames,

1. Double diagonal Bracing / X bracing

2. Chevron bracing /Inverted V bracing

3. V-bracing

4. K- bracing

5. Single diagonal bracing

The idea of use of outrigger is nowadays often utilized in tall structures. In this idea,

"outrigger” frames (sometimes, girders) are extended from the core to columns that resist

lateral load at the exterior section of the building. The center or core of the building may

comprise of either shear walls or trusses. It leads to an extremely efficient use of the

structural materials by improving the axial strength and stiffness of exterior columns to

resist part of the overturning moment produced by lateral forces. The bracing system

comprising of core with outriggers is most effective for tall structures in development of

strengths against wind and earthquake loads. In this way, the flexible nature of tall

structures can be reduced and also the structure will have controlled displacement and

inter-storey drift. The incorporation of the outrigger to the concrete core can be

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additionally upgraded by optimizing strengths into the outriggers. Based on the

connection to the outer columns, the system is of two types:

a) Conventional outrigger concept

b) Virtual outrigger concept

II. LITERATURE REVIEW

The study of structural performance of tall buildings during the past earthquakes

and wind loading gives the clear picture that these are the causes of irregularities in the

structure due to asymmetric distribution of mass, stiffness and strength, is the main

source of severe damage to the structures. In most of the studies the researches include

the study of use of lateral load resisting systems like bracings, outrigger and combination

of both bracings and outrigger in the building frames. A number of literatures associated

have been studied in detail and the highlights of each are reported below.

Kiran Kamath et al. [1] in this study three-dimensional 40 storey RCC building

with total height of 140m using ETABS. A variation of Hs/H proportion from 0.975 to

0.4 having relative stiffness between 0.25 and 2 was modeled and analyzed for static and

dynamic condition for a six different arrangements of outriggers. The static analysis is

carried out according to the lateral wind load IS-875-Part 3 (1987) and the equivalent

static analysis for seismic according to IS 1893-2002. Displacement is diminished by

37% by giving the outriggers at the top and it is lessened up to 61% by giving the

outriggers at midheight. There is 34% in decreased displacement at the top because of

seismic loads when the outrigger is installed at the top and it is diminished by 64% when

outriggers are set at the midheight (Hs/H). By the introduction of outriggers on each level

the shear force is negligible and also the peak acceleration is reduced upto 30%. Kiran

Kamath et al. [2] in this study three-dimensional structure having 40 stories, each storey

height is of 3.5 m and 140 m is the total height of the building . Results of lateral

displacements, storey drifts, shear forces and bending moments in the core wall are

obtained through ETABS analysis. When the displacement criteria are considered,

31.74% a reduction in the lateral displacement was observed at the top for the structure

with outrigger for a relative height of 1.5 as compared to the structure in the absence of

outrigger. Considering bending moment criteria, the bending moment is reduced by

32.60% when the outrigger structure is compared to a model without a model without

outrigger with a relative height of 6.67. Patil S.S et al. [3] the behavior of the moment

resist V-bracings(complete, partial bay tense and partial level tense and outrigger frame)

5 Bay 12-storey structures are modeled and numerically analyzed, in this study. In the

ninth level V braced completely which claim 7.70% and 7.87% saving in the material

cost respectively has been tried. The net saving in the cost of the structure is 14.31%. In

case of outriggers considering 12th levels and 7th levels braced at a time with the central

bay braced as before it is found that the net saving in the cost of the structure is 13.70%

and 13.23% respectively. It is concluded that Frames with combination of bay wise and

level wise bracing at a time (outrigger) give more economy as compared to bare frame

but give less economy as compared to the separate cases of bay wise and level wise

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braced frames. Maximum saving is found to be 14.31% as compared to bare frame.

Dhanaraj M. Patil and Keshav K. Sangle [4] in this study the seismic behaviour of the

outrigger braced system in high rise 2-D steel buildings has been studied with different

locations of the outrigger. Assessment of the structural performance of outrigger braced

high rise 2-D steel buildings of 20, 25, 30 and 35 storeys, with different locations of the

outrigger and Evaluation of seismic performance of different outrigger braced systems

under application of different invariant lateral load patterns in nonlinear static pushover

analysis. A nonlinear static pushover analysis is carried on example outrigger braced high

rise buildings using SAP2000v16 software. Example outrigger high rise buildings are

designed using IS1893 (Part-I):2002, IS875-1987 and IS800:2007. It concludes that

adding outrigger at 0.3H to 0.6H height of building increases stiffness thereby can resist

higher forces during seismic excitation. So optimum locations of the outrigger is 0.3H to

0.6H. Providing multi-outrigger is found to be very effective with one outrigger at the top

and another at the suggested height of buildings. Jagadish J. S and Tejas D. Doshi [5] a G

+15 storey steel frame building is used with different bracing systems such as Single-

Diagonal, X bracing, Double X bracing, K bracing, V bracing is used and analyzed using

STAAD.Pro, in this study. Seismic parameters such as displacement, base shear, axial

force, weight and storey drift of the structure are considered. It explains that According to

displacement criteria, braced frames are good at reducing displacement, and in the case of

K bracings and V bracings, the displacement is higher than without bracings due to

irregularity in the shape of the structure. A S Jagadheeswari and C Freeda Christy [6] In

this study a three-dimensional 40 storey building with 3 bays along x direction and 3 bays

along y direction with the typical storey height is 3.5m and total height of 140m is

considered. The structure consists of central core comprises shear wall with horizontal

girders or cantilever type trusses called outriggers made up of steel bracing, connecting to

the outer columns of building. The size of outrigger is 0.45m x 3.5m. For belt truss and

outrigger bracing ISLB250 structural steel is considered. The shape of outrigger bracing

and belt truss is X-shaped .A total of 9 different arrangements of outriggers by varying

Hs/H ratio has been modeled and analyzed using SAP2000 software. It is concluded that

the 20th and 26th storey (H2/H1=1.3) of the building is considered as the optimum

location of the building because overall the maximum displacement is effectively reduced

in this location. Shivacharan K et al. [7] In this study The Analysis of the tall building is

carried out to find the optimum position of outrigger system and belt truss by using

lateral loads. The three dimensional model is considered and designed for the gravity load

and placing of first and second position of the outrigger. Considering the design of Wind

load is calculated by using IS 875 (Part 3) and Design of Earthquake load is calculated by

using code IS 1893(part-1): 2000 in order to achieve reduction in drift, Deflection and

story shear. The analysis is done by considering tall vertical irregularity of 30th storey of

7 X 7 bay for 1 to 10th storey and 7X6 bay 11th to 20th storey and 7X5 Bay 21st to 30th

storey. It concludes that the by placing outrigger and belt-truss system in tall buildings

increases rigidity and also increases the load bearing capacity and makes the building

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efficient from lateral load. The maximum drift at the top of the structure when only core

employed is about 206.9 mm and is reduced by appropriately selecting the outrigger

system by placing them at 0,67 height is 130,4 mm. by placing second outrigger at 0.67h

results in the reduction of 16.64% and 13% for drift and deflection. The optimum

position is the midheight of the building for placing the second outrigger. Krunal Z.

Mistry et al.[8] In this study 40−storey 3D models of outrigger and belt truss systems are analyzed and compared to wind and earthquakes forces to find the lateral displacement

reduction associated with the outrigger and belt truss system. The ETABS software is

used and analyzed for a 150m tall steel concrete building frame, and arrangements of ten

different outriggers are considered. A 40-storey office building of plan area 42m x 42m

with columns spaced 6m from center to center is considered with a height of each storey

being 3m and keeping all floors as typical floors. It concludes that There is maximum

displacement reduction when 1st outrigger is placed at 20th floor i.e. at mid height and

maximum displacement reduction when 2nd outrigger is placed at 10th floor i.e. at 1/4th

height. There is also maximum reduction in drift index when 3rd outrigger is placed at

30th storey i.e. at 3/4th height of the building. P.M.B. Raj Kiran Nanduri et al.[9] In this

study, the use of outrigger and belt truss set at various location subjected to wind or

earthquake force. The position of outrigger and belt truss for decreasing lateral

displacement, moments and building drift can be achieved. The earthquake load was

obtained using IS 1893 (Part-1): 2002 and the wind load was calculated using IS 875

(Part-3). Analysis is carried out using ETABS software.The building models was

analysed for 30 stories with storey a height 3m . The bay-width along 2 horizontal

directions and the number of base are kept constant for all the model.In this study the

building considered here is a 90m tall reinforced concrete structure. A 30 storey office

building with a plan area of 38.5m × 38.5m with columns spaced at 5.5m from center to

center is the model used for analysis. The storey height is 3m and all the floors are

considered as typical Floors. It states that the utilization of outrigger and belt truss

framework in tall structures improves the rigidity and makes the structure safe under

lateral loading. By using second outrigger with cap truss gives the reduction in

displacement of 18.55% and 23.01% with and without belt truss. The ideal area of second

outrigger is midheight of the building. It can be infer that the optimum position of the

outrigger is 0.5 times the building height. Shruti B. Sukhdeve [10] A G+40 reinforced

concrete building was analysed using ETABS software. Building was analysed under

wind and earthquake loads as per the recommendation of IS: 875 (Part 3) 1987 and IS

1893 (Part 1) 2002 respectively. The building was analysed for Delhi city considering its

respective seismic zone basic wind speed. To improve the performance of building in

lateral load outrigger was provided. The analysis was carried out for building with

outrigger in the form of 300mm thick concrete wall provided at each floor from bottom to

top respectively. After running analysis the maximum deflection of building were

calculated and first position of outrigger were fixed at location where maximum

deflection reduction occurs as compare to building without outrigger. Then to find second

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position of outrigger first outrigger were fixed at its position and second outrigger were

provided at each floor from bottom to top respectively and maximum deflection reduction

were calculated. Same procedures were followed for third position of outrigger where

first and second outrigger positions were fixed and third outrigger were provided at each

floor from bottom to top respectively. Comparative graphs have been plotted for building

with and without outrigger. It concludes that the maximum deflection at top of structure

reduces up to 272.77mm by providing third outrigger at 1/3rd height of structure i.e.

54.98 % deflection reduction occurs for third position of outrigger. The Axial force goes

on decreasing as infill wall with different openings like corner and centre are provided.

With the application of lateral loads, tall buildings with outriggers shows higher stiffness

making the structure efficient. Outrigger system is not only efficient in controlling the

overall lateral displacement but also very capable of reducing the inter-storey drifts in tall

structures.

III. PROBLEM DEFINITION

The building in this project is a G+40 storey building and has been analyzed and

modelled using ETABS software by applying loads as per IS code requirements i.e.

Gravity loads, Imposed loads, lateral loads as per IS 456, IS 875, IS 1893. Analysis is

carried out for 40 storey bare steel frame structure, steel frame structure with X bracing

and Chevron bracing and also along with outriggers in addition to bracings at various

locations in the building. Static and dynamic linear analysis along with modal analysis is

carried out to obtain natural time period, storey displacement, storey drift, storey shear

and base shear.

The methodology consists of,

1. To carryout extensive literature review, to establish the objective of the study.

2. ETABS Software is used for the modeling and analysis of bare steel frame structure

for 40 storeys and steel frame structure with X bracing and Chevron bracing along

with outriggers.

3. Analyze the models using response spectrum analysis as per IS 1893-2002.

Comparing the parameters such as natural time period, storey displacement, storey

drift, storey shear and base shear.

4. Conclusions are made based on the performance of each structural system under

study.

IV. OBJECTIVES

To carry out the dynamic analysis on bare steel frame structure (equivalent static

analysis and response spectrum analysis).

To carry out the dynamic analysis on steel frames structure with chevron bracings.

To carry out the dynamic analysis on steel frames structure with double diagonal (X)

bracings.

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To carry out the dynamic analysis on steel frames structure with chevron bracings

along with outriggers at 13th, 26th and 40th storey level.

To carry out the dynamic analysis on steel frames structure with double diagonal

bracings along with outriggers at 13th, 26th and 40th storey level.

To carry out the dynamic analysis on steel frames structure with chevron bracings

along with outriggers at 10th, 20th and 30th storey level.

To carry out the dynamic analysis on steel frames structure with double diagonal

bracings along with outriggers at 10th, 20th and 30th storey level.

To study the seismic behaviour of all the models based on seismic parameters such as

time period, base shear, storey displacement, storey shear and storey drift.

To compare the results obtained from all the analysis carried out and hence quantify

the effectiveness of outrigger in braced steel structure.

To establish the better type of bracing amongst X and Chevron bracing that can be

adopted along with outriggers.

To observe the effect of variation of outrigger positions in the models and to compare

the results established by various researchers.

To check and establish the effectiveness of outriggers in the absence of a core frame

or core shear wall.

To fix the optimum positioning of outriggers.

V. MODELING AND ANALYSIS

The building in this project is a G+40 storey steel building and has been analyzed and

modelled using ETABS software by applying loads as per IS code requirements i.e.

Gravity loads, Imposed loads, lateral loads as per IS 456, IS 875, IS 1893. Analysis

will be carried out for the following seven models,

1. Bare steel frames structure

2. Steel framed structure with chevron bracings

3. Steel framed structure with X bracings

4. Steel framed structure with chevron bracings and outriggers at 13th, 26th and 40th

storey level.

5. Steel framed structure with X bracings and outriggers at 13th, 26th and 40th

storey level.

6. Steel framed structure with chevron bracings and outriggers at 13th, 26th and 40th

storey level.

7. Steel framed structure with X bracings and outriggers at 13th, 26th and 40th

storey level.

Static and dynamic linear analysis will be carried out to obtain natural time period,

storey displacement, storey drift, storey shear and base shear for all the seven models.

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Table 1: Building Modelling and Loading Data

1 Base Units kN-m

2 Type of Structure Steel Moment resisting frame with outrigger

braced

3 Grid Data Plan regular - Rectangle geometric shape

Grid Spacing Two bays of 6m and one 4m central bay

Total Dimension 16m x 16m Base dimension

Storey Height Uniform – 3 meters

No. of Stories 40

4 Material Properties Standard Values input in N-mm

Grade of Structural Steel FE 350

Grade of Concrete Deck M30

Poissons ratio 0.2

5 Frame Section Properties Standard Values input in N-mm

Column Built-up column

Beams ISMB

Wall/Slab Section properties Standard Values input in N-mm

Deck 200 mm

6 Static Loads kN/m2

Self-weight Considered

Super dead load (SDL) 2

Live load (Reducible) 4

Wall load (kN/m) Glazing load considered

7 Seismic Data Values as per IS 1893

Response Reduction

Factor (R)

4

Importance Factor (I) 1

Zone(z) 0.24 (IV)

Soil type II

8 Type of Analysis

Dynamic Analysis Response spectrum

Figure 1: Plan view of model

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Model 1: Bare steel frames structure

Figure-2: 3D-view of model

Model 2: Steel framed structure with chevron bracings

Figure-4: Elevation view

Figure-3: Plain view

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Model 3: Steel framed structure with X bracings

Figure-5: Plan view of model Figure-6: Elevation View

Model 4: Steel framed structure with chevron bracings and outriggers at 13th, 26th

and 40th storey level.


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Model 5: Steel framed structure with X bracings and outriggers at 13th, 26th and

40th storey level.


Model 6: Steel framed structure with Chevron bracings and outriggers at 10th, 20th

and 30th storey level.


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0

5

10

15

20

25

30

35

40

45

0 50 100 150 200 250 300

ST

OR

EY

NU

MB

ER

DISPLACEMENT (mm)

STOREY DISPLACEMENT

Bare Steel Frame Chevron bracing

X bracings Chevron bracing with outrigger (13-26-40)

X bracing with outrigger (13-26-40) Chevron bracing with outrigger (10-20-30)

Model 6: Steel framed structure with X bracings and outriggers at 10th, 20th and

30th storey level.


VI. RESULTS AND DISCUSSIONS

The results obtained from analysis are observed and graphs are plotted and compared

and discussed for all the seven models. The variation of seismic parameters like natural

period, story displacement, story drift, storey shear and base shear has been studied. By

comparing the results obtained the optimum location of outriggers is determined.

6.1 DISPLACEMENT:

Figure 15 : Variation of displacement

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The graph shows the variation of displacement of dynamic response spectrum

analysis in X direction between bare Steel framed structure, Chevron bracing Steel

framed structure, X bracing Steel framed structure, Chevron bracing with outiggers at

13th, 26th and 40th storey level, X bracing with outiggers at 13th, 26th and 40th storey

level, Chevron bracing with outiggers at 10th, 20th and 30th storey level and X bracing

with outiggers at 10th, 20th and 30th storey level. It can be inferred that X bracing with

outiggers at 10th, 20th and 30th storey level gives the least displacement of 154.54 mm

and bare Steel framed structure gives the maximum displacement 281.68 mm.

6.2 STOREY DRIFT:

Figure 16: Variation of Storey drift

The graph shows the variation of storey drift of dynamic response spectrum analysis

in X direction between bare Steel framed structure, Chevron bracing Steel framed

structure, X bracing Steel framed structure, Chevron bracing with outiggers at 13th, 26th

and 40th storey level, X bracing with outiggers at 13th, 26th and 40th storey level,

Chevron bracing with outiggers at 10th, 20th and 30th storey level and X bracing with

outiggers at 10th, 20th and 30th storey level. It can be inferred that X bracing with

outiggers at 10th, 20th and 30th storey level gives the least storey drift and bare Steel

framed structure gives the maximum storey drift.

0

5

10

15

20

25

30

35

40

45

0 0.001 0.002 0.003 0.004

ST

OR

EY

NU

MB

ER

DRIFT

STOREY DRIFT

Bare Steel FrameChevron bracingX bracingsChevron bracing with outrigger (13-26-40)X bracing with outrigger (13-26-40)

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012345678

Bare Steel

Frame

Chevron

bracing

X bracings Chevron

bracing with

outrigger

(13-26-40)

X bracing

with

outrigger

(13-26-40)

Chevron

bracing with

outrigger

(10-20-30)

X bracing

with

outrigger

(10-20-30)

Tim

e p

er

iod

mode

TIME PERIOD (s) Mode 1 Mode 2 Mode 3

6.3 TIME PERIOD:

Figure 17: Variation of time period

The graph shows the variation of time period in seconds between bare Steel

framed structure, Chevron bracing Steel framed structure, X bracing Steel framed

structure, Chevron bracing with outiggers at 13th, 26th and 40th storey level, X bracing

with outiggers at 13th, 26th and 40th storey level, Chevron bracing with outiggers at

10th, 20th and 30th storey level and X bracing with outiggers at 10th, 20th and 30th

storey level. It is inferred that X bracing with outiggers at 10th, 20th and 30th storey level

gives the least modes of time period and bare Steel framed structure gives the maximum

modes of time period.

5.4 BASE SHEAR :

Figure 18: variation of base shear

11801185119011951200120512101215

Bare Steel

Frame

Chevron

bracing

X bracings Chevron

bracing with

outrigger

(13-26-40)

X bracing

with

outrigger

(13-26-40)

Chevron

bracing with

outrigger

(10-20-30)

X bracing

with

outrigger

(10-20-30)

bA

SE

SH

EA

R

Base shear

RSX RSY

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The graph shows the variation of base shear between bare Steel framed structure, Chevron

bracing Steel framed structure, X bracing Steel framed structure, Chevron bracing with outiggers

at 13th, 26th and 40th storey level, X bracing with outiggers at 13th, 26th and 40th storey level,

Chevron bracing with outiggers at 10th, 20th and 30th storey level and X bracing with outiggers

at 10th, 20th and 30th storey level. The X bracing with outriggers gives maximum base shear and

the bare steel frame gives the least base shear.

VII. CONCLUSIONS AND SCOPE OF FURUTHER STUDY CONCLUSIONS

Based on the study conducted on various models of G+40 steel framed structure the

following conclusions can be drawn:

The use of chevron bracings reduces top storey displacement upto 25.62% when

compared to bare steel frame structure, whereas the use of X-bracings reduces 24.3%.

The use of chevron bracings increases the base shear by 0.25% and X bracings shows an

increase by 0.85%, when compared with bare steel frame structure.

It is observed that steel frame model with chevron bracings reduces drift upto 37.5%

when compared to bare steel frame structure, whereas the model with X bracings reduces

drift upto 37.8%.

From the above three conclusions it can be inferred that chevron bracings can be more

effective in high rise structures in controlling displacements and drifts without increasing

much of the base shear.

The use of outriggers at three different stories in addition to bracings is found to be very

effective in reducing the storey displacements.

It is found that use of steel frame structure with X bracings along with outrigger at 13th

,

26th

and 40th

storey level have reduced displacement upto 40.99% when compared to bare

steel frame structure, whereas X bracings along with outrigger at 10th

, 20th

and 30th

storey

level have reduced displacement upto 45.33%.

The top storey displacement could be reduced by 5.1% with a combination of X bracing

and outriggers at 10th

, 20th and 30th

storey when compared to outriggers at 13th

, 26th

and

40th

storey level.

It is also found that use of steel frame structure with X bracings along with outrigger at

13th

, 26th

and 40th

storey level have reduced drift upto 49.1% when compared to bare steel

frame structure, whereas X bracings along with outrigger at 10th

, 20th

and 30th

storey level

have reduced drift upto 54%.

The maximum storey drift reduced upto 11.1% in case of X bracing and outriggers at at

10th

,20th

and 30th


, 26th

and 40th

storey level.

The base shear has increased by 1.5% in case of X bracing with outriggers at 10th

,20th

and

30th

storey and also with outriggers at 13th

, 26th

and 40th

storey level.

From the above conclusions it can be inferred that with a combination of X bracings,

outriggers at 10th

, 20th

and 30th

storey performs better than outriggers at 13th

, 26th

and 40th

storey.

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It is found that use of steel frame structure with Chevron bracings along with outrigger at

13th

, 26th

and 40th

storey level have reduced displacement upto 38.7% when compared to

bare steel frame structure, whereas Chevron bracings along with outrigger at 10th

, 20th

and 30th

storey level have reduced displacement upto 44.3%.

The top storey displacement could be reduced by 6.4% with a combination of Chevron

bracing and outriggers at 10th

,20th

and 30th


,

26th

and 40th

storey level.

It is also found that use of steel frame structure with Chevron bracings along with

outrigger at 13th

, 26th

and 40th

storey level have reduced drift upto 47.2% when compared

to bare steel frame structure, whereas Chevron bracings along with outrigger at 10th

, 20th

and 30th

storey level have reduced drift upto 52%.

The maximum storey drift reduced upto 8.3% in case of Chevron bracing and outriggers

at 10th

,20th

and 30th


, 26th

and 40th

storey level.

The base shear has increased by 1.5% in case of Chevron bracing with outriggers at

10th

,20th

and 30th

storey and also with outriggers at 13th

, 26th

and 40th

storey level.

From the above conclusions it can be inferred that with a combination of Chevron

bracings, outriggers at 10th

, 20th

and 30th

storey performs better than outriggers at 13th

,

26th

and 40th

storey.

This study concludes that placing three outriggers at 10th

, 20th

and 30th

storey level is not

only proficient in controlling the overall lateral displacement but also very capable of

reducing the inter-storey drifts in tall building and hence for a G+40 steel structure

10th

,20th

and 30th

storey level can be considered as optimum position.

Hence it is also concluded that the use of bracings and outrigger system in high-rise

buildings increase the stiffness and makes the structural form efficient under lateral load.

Scope for further study

1. This study is based on the linear dynamic analysis therefore the results can be compared

with non-linear dynamic analysis of the building.

2. The dynamic analysis is carried out for G+40 storey building and the same dynamic

analysis can be out for G+50 storey and G+60 storey tall buildings.

3. The models may be compared by changing the type of soil and other zones to provide

better information about the response of the system.

4. Composite steel-concrete structure with concrete outrigger can be considered for this

study.

5. The K bracing and V bracings can be used and their effectiveness can be compared with

X bracings and Chevron bracings.

VIII. REFERENCES

[1] A S Jagadheeswari and C Freeda Christy, (2016) “Optimum Position of Multi Outrigger

Belt Truss in Tall Buildings Subjected to Earthquake and Wind Load”. Volume 09, No. 03,

P.P.373-377.

[2] Shruti B. Sukhdeve, (2016) “Optimum Position of Outrigger in G+40 RC Building” IJSTE

- International Journal of Science Technology & Engineering, Volume 2, Issue 10.

8537

ISSN: 2347-1697





[3] Krunal Z. Mistry, Proff. Dhruti J. Dhyani, (2015) “Optimum Outrigger Location In

Outrigger Structural System For High Rise Building”, International Journal of Advance

Engineering and Research Development ,Volume 2, Issue 5.

[4] Shivacharan K, Chandrakala S, Narayana G, Karthik N M, “(2015)Analysis Of Outrigger

System For Tall Vertical Irregularites Structures Subjected To Lateral Loads”, IJRET:

International Journal of Research in Engineering and Technology, Volume: 04, Issue: 05.

[5] Dhanaraj M. Patil and Keshav K. Sangle, (2015) “Seismic Behaviour of Different Bracing

Systems in High Rise 2-D Steel Buildings”, Structures, 3, PP 282-305.

[6] Kiran Kamath, Avinash A.R., Sandesh Upadhyaya K, (2014) “A Study on the Performance

of Multi-Outrigger Structure Subjected to Seismic Loads. PP 27-32.

[7] Karthik.N.M, N.Jayaramappa, (2014) “optimum position of Outrigger system for High

Raised RC Buildings using etabs 2013.1.5 (push over analysis)”, International Journal of

Advanced Technology in Engineering and Science, Volume No.02, Issue No. 12.

[8] Jagadish J. S and Tejas D. Doshi, (2013)” A Study On Bracing Systems On High Rise Steel

Structures” Vol. 2 Issue 7.

[9] Patil S.S., Aland S.S., Kore P.N, (2013)” Seismic Response of Concentrically Barced

Reinforced Concrete Frames” Volume 4, Issue 7.

[10] P.M.B. Raj Kiran Nanduri1, B.Suresh, MD. Ihtesham Hussain, (2013) “Optimum Position

of Outrigger System for High-Rise Reinforced Concrete Buildings Under Wind And

Earthquake Loadings”, American Journal of Engineering Research (AJER) e-ISSN: 2320-

0847 p-ISSN: 2320-0936 Volume-02, Issue-08, pp-76-89.

[11] Kiran Kamath, N. Divya and Asha U. Rao, (2012) “A Study on Static and Dynamic

Behaviour of Outrigger Structural System for Tall Buildings”, Bonfring International

Journal of Industrial Engineering and Management, Vol 2, No. 4, PP 15-20, December

[12] Indian Standard Code of Practice for Design Loads (other than earthquake) For Buildings

and Structures, Part – 3 Wind Loads, IS: 875 (Part 3) – 1987 (Second Revision), Bureau of

Indian Standards, New Delhi, India.

[13] Indian Standard Criteria for Earthquake Resistant Design of Structures, IS: 1893 (Part 1)

2002, Part 1 General Provisions and Buildings (Fifth Revision), Bureau of Indian

Standards, New Delhi, India.

TO CITE THIS PAPER

Gulhane, L.G. (2017) :: “Correlative Study of Anxiety and Study Habits with Academic

Achievement of Secondary Students” International Journal of Informative & Futuristic

Research (ISSN: 2347-1697), Vol. (4) No. (11), July 2017, pp. 8434-8441, Paper ID:

IJIFR/V4/E11/082. Available online through- http://www.ijifr.com/searchjournal.aspx

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Dynamic Analysis of Outrigger Braced Systems in High …ijifr.com/pdfsave/19-08-2017140IJIFR-V5-E12-007.pdfhave been studied in detail and ... In this study The Analysis of the tall