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International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 8, August 2017, pp. 609–616, Article ID: IJCIET_08_08_062

Available online at http://http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=8&IType=8

ISSN Print: 0976-6308 and ISSN Online: 0976-6316

© IAEME Publication Scopus Indexed

A COMPARATIVE STUDY ON EFFECT OF

LATERAL LOADING ON STEEL BRACED

REINFORCED CONCRETE STRUCTURE OF

UNSYMMETRICAL BUILDING PLAN

M. Prasanna Kumar

Assistant Professor Sr-Scale, Department of Civil Engineering, Manipal Institute of

Technology, Manipal University, Manipal, Karnataka, India,

Raja Madhukar Vishnu

Post Graduate Student, Department of Civil Engineering, Manipal Institute of Technology,

Manipal University, Manipal, Karnataka, India

ABSTRACT

Steel bracings are lateral load resisting structural members which help in increase

of strength and satisfy both architectural and structural requirements considering

gravity and lateral loads. Present analytical research deals with optimum location of

bracing and bracing system in unsymmetrical building plan (T-shape) of G+30

storeys by considering both wind and seismic effect. Bracings such as X and single

diagonal are compared and provided at various exterior locations of structure. In the

present research the comparison is done for five different types of bracings system

such as braces are connected within the storey is type 1, In type 2- bracing are

connected between two storeys, in type 3- bracing are connected between three

storeys, type 4- bracing are connected between four storeys, type 5- bracing are

connected between five storeys. The results are compared with bare frame and steel

braced structure considering ductility, drift control and torsional effect. The analytical

results concluded that providing more stiffness leads to control of drift, reduces

ductile nature and increase of torsional effect. Bracings connecting for more than two

stories increases ductility, reduces stiffness and reduces torsional effect- compared to

bracing connected within the storey.

Keywords: Ductility, Steel bracing, RC structure, Response Spectrum Analysis,

Torsional effect, Unsymmetrical Building Plan,

Cite this Article: M. Prasanna Kumar and Raja Madhukar Vishnu, A Comparative

Study on Effect of Lateral Loading on Steel Braced Reinforced Concrete Structure of

Unsymmetrical Building Plan, International Journal of Civil Engineering and

Technology, 8(8), 2017, pp. 609–616.

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=8

M. Prasanna Kumar and Raja Madhukar Vishnu


1. INTRODUCTION

Functionality of all kinds of structural forms is to transfer gravity load effectively and

structure should resist lateral load caused by wind and seismic forces. Lateral loads influences

structure in developing high stresses and more sway in order to overcome this problem a

lateral force resisting systems such as bracings, shear wall are used to increase the strength of

RC framed structures and control structural damage caused by earthquake.

Today to serve serviceability conditions architects are preferring irregularities for

aesthetic and other conditions. The shape and proportion of the structure effects the

distribution of forces. Due to irregularities structure causes deficient in stiffness, continuous

load path and also tension capacity will be less at re-entrant corners.

In braced frame structures lateral loading is resisted by diagonal members which

transforms the system into girders with web of vertical truss and columns acting as chords.

Diagonal members provide high stiffness to the structure and resist lateral forces by

developing internal axial tensile or compressive actions.

Raja et-al (2015) done performed dynamic analysis considering steel bracing for

unsymmetrical building plan of G+30 storeys. They compared performance of the structure

considering bracing within storey and more than one storey. They concluded that ductile

nature increases when bracings are connected for more than one storey [13] .Raja et-al (2015)

performed research on linear static and response spectrum analysis considering

unsymmetrical building plan of G+30 storeys. They provided internal braces to the structure.

They concluded that X and inverted V braces provide good stiffness and control

displacements but base shear increases [12]. Kadid and Yahiaoui (2011) done research on the

static non-linear pushover analysis of three and six storied RC structure considering X,

inverted V, ZX, and Zipper braces. They concluded that selection of section for steel bracing

effects the global capacity of building and X, Zipper braces provides good results [1]. Badoux

and James (1990) done experimental and analytical research on the retrofitting of steel

bracing for RC frame. The analytical study focusing inelastic response of plane structures

subjected to seismic loading. They concluded that steel bracing is well suited for lateral

strengthening of multistorey RC structure from drift and collapse prevention. Combining

bracing with beam provides significant improvement in elastic behaviour of braced frame [2].

Murali and Arunakanthi (2013) performed an analytical research of optimum location of shear

wall for unsymmetrical building plan using linear static and response spectrum analysis. They

concluded that providing different shapes of shear walls effects the eccentricity, time period,

controls displacement and dynamic analysis is necessary for evaluating actual performance of

the structure [3]. Pincheira, and James (2014) conducted study on seismic performance of

non-ductile reinforced concrete (RC) frames using inelastic static and dynamic response

analyses for five ground motions representative of major earthquakes on firm and soft soil

conditions of 3,7 and 12 storied RC frames using DRAIN-2D. They concluded that steel

braces would adversely affect lateral strength of reinforced concrete member [5]. Maheri,

Kousari and Razazan (2011) conducted experimental research on ductile nature of RC frames

with X and Knee braces. They concluded that X and Knee braces increases strength and

capacity. X increases stiffness and decreases ductility and Knee bracing provides good

ductility [7]. In the present investigation two different types of bracing systems X, and single

diagonal braces are considered to the structure and models are divided into five different types

and results are compared considering all the five types.

2. MODELLING INFORMATION:

Building plan is T-shape, No. of stories- G + 30, Height of Building 105.6 m, Length of

building 40m(unsymmetrical along X Direction), 40 m(symmetrical along Y Direction),

A Comparative Study on Effect of Lateral Loading on Steel Braced Reinforced Concrete Structure of

Unsymmetrical Building Plan


Material Properties: Grade of concrete M40, Grade of steel 415, Density of reinforced

concrete 25 KN/m 3, Thickness of slab 0.150 m, Beam Cross Section 0.3m X 0.9 m,

Plinth Beam Cross Section 0.3m X 0.75m, Column Cross Section 1.2m X 1.2m, (Up

to storey 10), 1.0m X 1.0m (11 to 20 storey), 0.8m X 0.8m (21 to 30 storey), Steel Bracing

SectionISA 200X200X25 [12]. Rigid diaphragms are provided to the structure. Figures 1,

2,3,4,5 and 6 are taken from [12]. In the present investigation two different types of bracing

systems X, and single diagonal braces are considered to the structure and models are divided

into five different types. In type 1 bracing is connected within the storey and results are taken

from [12]. In type 2 bracing are connected between two storeys, type 3 three storeys, type 4

four storeys, type 5 five storeys. Results are compared considering all the five types. In each

type there are 8 models (figure 2, 3, 4 and 5) and model 1 is bare frame (fig: 1). Fig: 6 isthe

elevation of each type considering X bracing. Loading condition: Live Load 3 KN/m2,

Floor Finish 1.5 KN/m2,

Seismic Loading Conditions: Zone-V, Soil Type- Medium, Importance Factor- 1, Response

reduction- 5%,

Wind Loading Conditions: Wind Speed 47m/s, Terrain Category- 1, Structure Class- C,

Topography factor (k3)-1.2 [12].Table 1 Historical tsunami that affected the western coast of

India

Figure 1 Top view of Model1 (Without steel bracing)

Figure 2 Top view of Model 2 (X bracing) and Model 3 (Single Diagonal bracing)




(a) (b) (c) (d) (e)

Figure 6 Elevation view of five types of models (a) Type-1, (b) Type-2, (c) Type-3, (d) Type-4, (e)

Type-5.

3. RESULTS AND DISCUSSION

The response of structure was compared considering time period, eccentricity, torsion and

storey drift.

Figure 7 Time period considering all models

Time period is very important parameter for ductile behaviour of a structure. As the time

period increases ductile nature increases and collapse time also increases. From fig: 7 we can

observe that when compared to bare frame (model 1) time period of other models is

decreased. There is increasing trend in time period for type 1 to type 5. So by connecting

bracing for more than one storey improves ductile nature.

3

3.2

3.4

3.6

3.8

4

4.2

4.4

4.6

4.8

5

1 2 3 4 5 6 7 8 9

TIM

E P

ER

IOD

(se

c)

MODEL NUMER

TYPE 1

TYPE 2

TYPE 3

TYPE 4

TYPE 5



Figure 8 Eccentricity along Y-direction considering all models

Eccentricity is distance between center of mass and center of stiffness of a structure.

Basically it happens when building has irregularities. From figure 8 we can observe that when

compared to model 1 in type 1 eccentricity is maximum and decreases from type 2 and

minimum in type 5. Hence by provide required stiffness and mass then eccentricity can be

decreased.

Figure 9 Maximum storey torsion along X-direction considering all models

Figure 10 Maximum storey torsion along Y-direction considering all models

Torsion depends upon eccentricity. From figure 9 and 10 we can observe that when

compared to model 1 in type 2 torsion is maximum and decreases from type 3 and minimum

in type 5. by connecting bracing for more than one storey torsion decreases.

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

1 2 3 4 5 6 7 8 9

EC

CE

NT

RIC

TY

(m)

MODEL NUMBER

TYPE 1

TYPE 2

TYPE 3

TYPE 4

TYPE 5

275000

300000

325000

350000

375000

400000

425000

450000

475000

500000

525000

1 2 3 4 5 6 7 8 9

ST

OR

EY

TO

RS

ION

(KN

-m)

MODEL NUMBER

TYPE 1

TYPE 2

TYPE 3

TYPE 4

TYPE 5

275000

300000

325000

350000

375000

400000

425000

450000

475000

1 2 3 4 5 6 7 8 9

ST

OR

EY

TO

RS

ION

(KN

-m)

MODEL NUMBER

TYPE 1

TYPE 2

TYPE 3

TYPE 4

TYPE 5




Figure 11 Maximum storey drift considering DL+WLX load combination

Figure 12 Maximum storey drift considering DL-WLY load combination

Storey drift is controlled by increase of stiffness. From figure 11 and 12 we can observe

that in type 1 controls maximum drift because stiffness is maximum. For type 2 drift

decreases because stiffness is less when compared to type 1.

4. CONCLUSION

1. Time period increases when connectivity of bracing is more than one storey. There by

improving ductile nature of the building.

2. Eccentricity decreases when connectivity of bracing is more than one storey. Hence by

provide required stiffness and mass then eccentricity can be decreased.

3. Torsion decreases when connectivity of bracing is more than one storey. Here

eccentricity decreases when connected more than one storey. Single diagonal bracing

provides good results when connected to five storeys both along X and Y directions

4. Storey drift decreases when connectivity of bracing is more than one storey. Here

stiffness decreases when connectivity of bracing is more than one storey. X bracing

provides good results when connected to within the storey both along X and Y

directions.

5. X bracing provides maximum stiffness and mass but single diagonal bracing provides

less stiffness and mass.

6. Providing required stiffness and checking ductile nature is very important to a

structure. Reducing mass of a structure improves ductility.

0.0007

0.0009

0.0011

0.0013

0.0015

0.0017

0.0019

0.0021

1 2 3 4 5 6 7 8 9

MA

XIM

UM

ST

OR

EY

DR

IFT

(m)

MODEL NUMBER

TYPE 1

TYPE 2

TYPE 3

TYPE 4

TYPE 5

0.0006

0.0008

0.001

0.0012

0.0014

0.0016

0.0018

1 2 3 4 5 6 7 8 9

MA

XIM

UM

ST

OR

EY

DR

IFT

(m)

MODEL NUMBER

TYPE 1

TYPE 2

TYPE 3

TYPE 4

TYPE 5



REFERENCES

[1] A.Kadid and D.Yahiaoui,“Seismic Assessment of Braced RC Frames”, Procedia

Engineering, Volume No. 14, PP. 2899-2905, 2011.

[2] Marc Badoux and James O.Jirsa, “Steel Bracing for RC Frames for Seismic Retrofitting”,

Journal of Structural Engineering (ASCE), Volume No. 116 Issue No.1, pp- 55-74,1990.

[3] A.Massumi and M.Absalan “Interaction between bracing system and moment resisting

frame in braced RC frames”, Archives Of Civil and Mechanical Engineering, Volume No.

13, PP. 260- 268, 2013.

[4] Jose A.Pincheira and James O.Jirsia, “Seismic Response of RC Frames Retrofitted with

steel braces Or walls”, Journal of Structural Engineering (ASCE), Volume No. 121 Issue

No.8, pp- 1225- 1235,1995.

[5] A.murali Krishna and Dr.E.Arunakanthi “Optimum Location of Different Shapes of Shear

Walls in Unsymmetrical High Rise Buildings”, International Journal of Engineering

Research and Technology Volume No.3 Issue No.9, ISSN 2278-0181,2014.

[6] T.Mahdi and V.Bahreini,“Seismic response of Asymmetrical Infilled concrete frames”,

Procedia Engineering, Volume No. 54, PP. 341-352, 2013.

[7] M.R.Maeri, R.Kousari and M.Razazan,“Pushover tests on steel X-braced and Knee braced

RC frames”, Engineering structures, 2011

[8] S.Bungale and Ph.D.S.E.Taranath, Wind and Earthquake Resistant Buildings Structural

Analysis and Design, Marcel Dekker, 2005.

[9] Bureau of Indian Standards, IS 456:2000-code of practice for Plain and Reinforced

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[10] Bureau of Indian Standards, IS 1893 (Part 1): 2002 criteria for earthquake resistant design

of structures, fifth revision, June 2002.

[11] Bureau of Indian Standards, IS 800:2007 –code of practice for General Construction in

Steel, third revision, December 2007.

[12] Raja Madhukar Vishnu, M.Prasanna Kumar, Y.Balakoti Reddy,“Seismic Response of

steel braced RC structure of Unsymmetrical building”, International Conference On

Advances in Civil Engineering Materials and Processes at Coimbatore Institute Of

Technology during 7th,8th and 9th of January 2015.

[13] Raja Madhukar Vishnu, M.Prasanna Kumar, Y.Balakoti Reddy and A.Murali

Krishna,“Dynamic analysis of steel braced RC structure of Unsymmetrical building plan”,

International Conference On Earth Science and Engineering at Nehru Institute Of

Technology during 20th and 21st of March 2015.

[14] Santhosh H.P, Harsha M.S, Manohar K and Pradeepa B.B, Seismic Isolation of RC

Framed Structure with and without Infills. International Journal of Civil Engineering and

Technology, 8(2), 2017, pp. 316–327.

[15] Anusha Kudumula, Dr. Vaishali G Ghorpade and Dr. H. Sudarsana Rao, Seismic

Performance of RC Framed Buildings Under Linear Dynamic Analysis. International

Journal of Civil Engineering and Technology, 8(1), 2017, pp. 09–16.

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