earthquake resistant design of low-rise open ground storey framed building … · 2017-04-07 ·...

@IJMTER-2015, All rights Reserved 94

EARTHQUAKE RESISTANT DESIGN OF

LOW-RISE OPEN GROUND STOREY FRAMED BUILDING

ADITYA DESHMUKH1

1P.G. Student (M-Tech - Structures), Nagpur University, Maharashtra

Abstract - Present study RC framed building (G+10) with open ground storey located in Seismic Zone-

II, III, IV and V is considered. The main objective of present study is the study of strengthing

performance of Open ground storey(OGS) buildings according to various cases such as: (a) bare frame

building (b)building with uniform infill in all storey (c) building with OGS (d) OGS with stiffer column

(e) OGS with corner shear wall (f) OGS with corner cross bracing (g) OGS with composite columns.

The separate models were generated using commercial software ETABS. Infill stiffness was modeled

using an equivalent diagonal strut approach. Parametric studies on displacement, storey drift, shear

force, bending moment and base shear have been carried out using equivalent static analysis to

investigate the influence of this parameter on the behavior of building with OGS.

Keywords – stiffness, infill wall, equivalent diagonal strut, strengthing of OGS building, seismic

analysis

I. INTRODUCTION

In general, multi-storeyed Reinforced concrete (RC) frame buildings in metropolitan cities require open

taller first storey for parking of vehicles i.e., columns in the ground storey do not have any partition

walls (of either masonry or RC) between them and/or for large space for meeting room or a banking hall

owing to lack of horizontal space and high cost are becoming increasingly common in India. Such

buildings are know as open ground storey buildings or stilts storey building. Open ground storey

buildings are inherently poor systems with sudden drop in stiffness and strength in the ground storey. In

the current practice, stiff masonry walls are neglected and only bare frames are considered in design

calculations. Thus, the inverted pendulum effect is not captured in design.

II INDIAN STANDARD IS 1893-2002

Stiffness Irregularity( soft storey) : a soft storey is one in which the later stiffness is less than 70

percent of that in storey above or less than 80 percent of the average lateral stiffness of the three storey

above

Stiffness Irregularity( Extreme soft storey) : a extreme soft storey is one in which the later stiffness is

less than 60 percent of that in storey above or less than 70 percent of the average lateral stiffness of the

three storey above. For example, building on STILTS will fall under this category

Clause 7.10.3 : The column and beams of the soft storey are to be designed for 2.5 times the storey

shears and moments calculated under seismic loads specified in the other relevant clauses.

III OBJECTIVE OF THE STUDY

Based on the literature review the salient objectives of the present study have been identified as follows:

International Journal of Modern Trends in Engineering and Research (IJMTER) Volume 02, Issue 04, [April – 2015] ISSN (Online):2349–9745 ; ISSN (Print):2393-8161


The effect of masonry infill stiffness in the seismic analysis of Open ground storey buildings.

Strengthening of Open Ground Story RC buildings.

IV. STRUCTURAL MODELLING

It is very important to develop a computational model on which analysis is performed. In this regard,

ETBAS software has been considered as tool to perform. Hence we will discuss the parameters defining

the computational models, the basic assumptions and the geometry of the selected building considered

for this study. A detailed description on the modeling of RC building frames is discussed. Infill walls are

modeled as equivalent diagonal strut elements.

An OGS framed building located at India (Seismic Zone I, II, IV, and V) is selected for the present

study. The building is fairly symmetric in plan and in elevation.

.

Fig 1 - Typical floor plan of the selected building

In the present study different building components are modeled as described below Using Software. In

this study the seven models are studied as described below

Case1- Bare Frame Building Case2- Building with

Uniform-Infill in All Storey



Case3- Building with Open

Ground Story

Case4- OGS with Stiffer

Column (MF 2.5)

Case5- OGS with Corner

Shear wall

Case6- OGS with Cross

Bracing

Case7- OGS with Composite

Column



BUILDING DESCRIPTION

Plan dimensions : 31 m x 22m

Number of Storey : G+10

Total height of building : 33 m

Floor height : 3 m

Beam sizes : 300 x 500 mm

Column sizes : 300 x 600 mm

Slab thickness : 150 mm

Floor Live Load : 3 kN/m2

Roof live load : 1.5 kN/m2

Floor Finish Load : 0.5 kN/m2

Concrete grade : M25

Steel : Fe415

Earthquake parameters

Seismic zone : II, III, IV and V

Response Reduction Factor : 5

Importance Factor : 1

Type of soil : Medium

Damping of structure. : 5%

Modeling of Infill Walls In present study, infills wall in stories are modeled as equivalent diagonal strut (Proposed by Hendry in

1998) and its equivalent width (W) of a strut is given as,



To determine αh and αl which depends on the relative stiffness of the frame and on the geometry of the

panel.

Where,

Em and Ef = Elastic modulus of the masonry wall and frame material, respectively

t, h, l = Thickness, height and length of the infill wall, respectively

Ic, Ib = Moment of inertia of the column and the beam of the frame, respectively

Ѳ = tan-1(h/L)

V. RESULT AND DISCUSSION

Later Displacement :-

The later displacement in columns in X-direction and Y-direction direction is considered for

analysis in seismic zone II, III, IV, and V shown in graphical representation of data is shown in Graph

no. 1 to 8

Graph 1 : Zone II, X-direction Graph 1: Zone II, X-direction

Graph 3 : Zone III, X-direction Graph 4 : Zone III, Y-direction

0

5

10

15

20

25

30

35

0 2 4 6 8 10 12

Dis

pla

ce

me

nt (

mm

)

Floor Level

Variation in X-Displacement Floorwise

CASE 1 CASE 2 CASE 3 CASE 4 CASE 5 CASE 6 CASE 7

0

5

10

15

20

25

30

35

40

45

0 2 4 6 8 10 12

Dis

pla

ce

me

nt (

mm

)

Floor Level

Variation in Y-Displacement Floorwise


0

5

10

15

20

25

30

35

40

0 2 4 6 8 10 12

Dis

pla

ce

me

nt (

mm

)

Floor Level



0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12

Dis

pla

ce

me

nt (

mm

)

Floor Level





Graph 5 : Zone IV, X-direction Graph 6: Zone IV, Y-direction

Graph 7 : Zone V, X-direction Graph 8 : Zone V, Y-direction

For comparison of the later displacement of the selected building, plots of the storey level displacement

in X-direction or Y-direction versus height are made for the seven cases, all imposed on the same graph.

The displacement is inversely proportional to the stiffness.

From the graphs it is observed that the displacements are large occurs in case of open ground storey

building (case 3).

In case 2, case 4, case 5, case 6 and case 7 displacement are reduced as compared to case 3 (open

ground storey).

Percentage reduction in displacement with respect to case 3 (OGS)

In zone II

Displacement Case 2 Case 4 Case 5 Case 6 Case 7

% reduction 25 47 58 22 25

In zone III

Displacement Case

2

Case

4

Case

5

Case

6

Case

7

% reduction 40 48 71 23 25

In zone IV

Displacement Case

2

Case

4

Case

5

Case

6

Case

7

% reduction 48 48 71 24 25

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12

Dis

pla

ce

me

nt (

mm

)

Floor Level



0

10

20

30

40

50

60

0 2 4 6 8 10 12

Dis

pla

ce

me

nt (

mm

)

Floor Level



0

10

20

30

40

50

60

0 2 4 6 8 10 12

Dis

pla

ce

me

nt (

mm

)

Floor Level



0

10

20

30

40

50

60

70

80

0 2 4 6 8 10 12D

isp

lace

me

nt (

mm

)Floor Level





In zone V

Displacement Case

2

Case

4

Case

5

Case

6

Case

7

% reduction 52 50 71 26 30

Percentage reduction of displacement is more in Case 5 as compared to other Cases. So the best model

of OGS building with corner shear wall (case5)

Bending Moment

The bending moment in columns in X-direction and Y-direction direction is considered for analysis in

seismic zone II, III, IV, and V shown in graphical representation of data is shown in Graph no. 9 to16

Graph 9 : Zone II, X-direction Graph 10 : Zone II,Y-direction

Graph 11: Zone III, X-direction Graph 12: Zone III,Y-direction

Graph 13 : Zone IV, X-

direction Graph 14 : Zone IV, Y-

direction


Story 1 15.5 24.1 87.8 93.8 26.9 44.8 75.6

Story 2 13.2 27.4 38.0 42.2 23.2 40.9 43.2

0

10

20

30

40

50

60

70

80

90

100

Be

nd

ing

Mo

me

nt (

KN

-m)

Variation in X-Bending Moment Modelwise


Story 1 16.4 28.3 93.8 79.8 39.5 57.1 74.2

Story 2 8.2 30.9 47.6 58.8 36.5 46.0 52.6

0

10

20

30

40

50

60

70

80

90

100

Be

nd

ing

Mo

me

nt (

KN

-m)

Variation in Y-Bending Moment Modelwise


Story 1 26.5 44.1 191.1 181.3 82.3 120.7 164.1

Story 2 22.0 50.0 119.5 135.7 68.1 106.1 133.5

0

50

100

150

200

250

Be

nd

ing

Mo

me

nt

(KN

-m)



Story 1 29.5 31.2 106.4 97.5 44.2 58.9 86.3

Story 2 19.9 23.6 69.9 75.3 41.7 47.8 60.6

0

20

40

60

80

100

120

Be

nd

ing

Mo

me

nt (

KN

-m)



Story 1 69.9 88.7 262.1 233.2 122.0 159.2 172.0

Story 2 40.4 112.6 170.4 190.0 102.6 130.5 117.5

0

50

100

150

200

250

300

Be

nd

ing

Mo

me

nt (

KN

-m)



Story 1 36.6 40.1 183.0 170.4 62.3 90.3 109.1

Story 2 25.5 32.6 78.9 98.7 54.5 68.9 76.1

0

20

40

60

80

100

120

140

160

180

200

Be

nd

ing

Mo

me

nt (

KN

-m)




Graph 15 : Zone V, X-direction Graph 16 : Zone V, Y-

direction

The bending moment is maximum in ground storey columns as compared to above storeys in case of

OGS building (case 3).

In open ground story with corner shear wall and open ground story with corner cross bracing the

moment are reduces by approximate 50-70% as compare to open ground storey building and very

effective from strength point of view these cases.

From the graphs it is observed that stiffer column and composite column (case 4 and case 7) increases

the bending moment in the ground storey column.

Storey Drift

The storey drift in columns in X-direction and Y-direction direction is considered for analysis in

seismic zone II, III, IV, and V shown in graphical representation of data is shown in Graph no. 17 to 24

Graph 17 : Zone II, X-direction Graph 18: Zone II, Y-direction

Graph 19 : Zone III, X-

direction

Graph 20 : Zone III, Y-

direction


Story 1 107.9 161.9 358.7 340.1 185.5 245.6 265.1

Story 2 68.0 185.4 226.2 240.9 188.3 203.2 163.5

0

50

100

150

200

250

300

350

400

Be

nd

ing

Mo

me

nt (

KN

-m)



Story 1 42.1 78.6 248.1 246.5 90.6 145.8 194.2

Story 2 40.0 52.4 139.2 180.0 78.3 99.8 112.6

0

50

100

150

200

250

300

Be

nd

ing

Mo

me

nt (

KN

-m)


0

0

0

1

1

1

1

1

2

2

0 2 4 6 8 10 12

Drif

t (

mm

)

Floor Level

Variation in X-Drift Floorwise


0

1

1

2

2

3

0 2 4 6 8 10 12

Drif

t (

mm

)

Floor Level

Variation in Y-Drift Floorwise


0

1

1

2

2

3

0 2 4 6 8 10 12

Drif

t (

mm

)

Floor Level



0

1

1

2

2

3

3

4

4

0 2 4 6 8 10 12

Drif

t (

mm

)

Floor Level





Graph 21 : Zone IV, X-

direction

Graph 22 : Zone IV, Y-

direction

Graph 23 : Zone V, X-direction Graph 24 : Zone V, X-

direction

From the graphs it is observed that the storey drift is large for open ground storey (case 3).

Storey drift profile becomes smooth from case 4 to case 7 indicating more stiffness.. Stiffer columns

(case 4) and composite column (case 7) reduces the storey drift at first floor level.

Base Shear

The base shear in columns in X-direction and Y-direction direction is considered for analysis in seismic

zone II, III, IV, and V shown in graphical representation of data is shown in Graph no. 25 to 28

Graph 25 : Zone II Graph 26 : Zone III

0

1

1

2

2

3

3

4

4

0 2 4 6 8 10 12D

rif

t (

mm

)

Floor Level



0

1

2

3

4

5

6

0 2 4 6 8 10 12

Drif

t (

mm

)

Floor Level



0

1

2

3

4

5

6

0 2 4 6 8 10 12

Drif

t (

mm

)

Floor Level



0

1

2

3

4

5

6

7

8

9

0 2 4 6 8 10 12

Drif

t (

mm

)Floor Level




X-direction 1451 8191 5032 6391 7072 5441 5727

Y-direction 1068 6311 3588 5020 5710 4132 3859

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

Ba

se

Sh

ea

r (

KN

)

Variation in Base Shear Building Modelwise


X-direction 2321 13105 8051 10226 11315 8705 9163

Y-direction 1709 10098 5740 8032 9135 6611 6175

0

2000

4000

6000

8000

10000

12000

14000

Ba

se

Sh

ea

r (

KN

)




Graph 27 : Zone IV Graph 28 : Zone V

The base shear is directly proportional to weight of structure

From the graphs base shear profiles it is observed that minimum shear occurs in open ground storey

building (case 3).

It is observed that the use of uniform infill in all storeys in the first storey increase the base shear up to

68% as compared with case3. Stiffer column and beam (case 4) increase the base shear to 33% of case

3. By introducing Corner shear wall (case 5) increase the base shear to 45% of case 3. Corner cross

bracing (case 6) increase the base shear to 12% of case 3. Composite column and beam (case 7) increase

the base shear to10% of case 3.

VI. CONCLUDING REMARKS

1. Underestimation of design base shear in case of bare frame models as compared to the infill

models the design base shear increases with increase in mass and stiffness of masonry infill wall and

vice versa.

2. Infill panel increases the later stiffness of the building, measured in terms of first story

displacement there by reducing displacement in all storey levels compared to open ground story building

cases.

3. Open ground story with shear wall and cross bracing are found to be very effective in reducing

the stiffness irregularity and bending moment in the column.

4. Open ground story with stiffer column and composite columns are effective in reducing the

stiffness irregularity and drift, but there is increase in the shear force and bending moment in the first

story.

5. Ductility if found more in the infill frame panel compare to the open ground story building

models.

REFERENCES Journal paper: 1. Holmes, M. (1961) Steel frames with brick and concrete infilling. Proceedings of Institution of Civil Engineers.

2. Arlekar, J.N.; S. K. Jain and C.V.R Murty (1997) Seismic response of RC frame buildings with soft first storeys.

Proceedings of CBRI golden jubilee conference on natural hazards in urban habitat. New Delhi

3. Riddington, J. R. and S. B. Smith (1977) Analysis of infilled frames subject to racking with design recommendations.

The Structural Engineer.

4. Davis, P. R., (2009) Earthquake Resistant Design of Open Ground Storey RC Framed Buildings. Ph.D. Thesis, Indian

Institute of Technology Madras, Chennai.

5. Smith, S. B. (1966) Behaviour of Square Infilled frames. ASCE Journal of the Structural Division. 92. 381-403

6. S. B. Smith and C. Carter, (1969) A Method of Analysis for Infilled Frames. Proceedings of Institution of Civil

Engineers.

7. P.B.Lamb, Dr R.S. Londhe(2012) Seismic Behavior of Soft First Storey, Proceedings of IOSR Journal of Mechanical

and Civil Engineering.


X-direction 3482 19658 12076 15339 16972 13057 13745

Y-direction 2564 15147 8611 12049 13703 9916 9262

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

Ba

se S

he

ar

(KN

)



X-diretion 5223 29487 18114 23008 25458 19586 20617

Y-direction 3845 22721 12916 18073 20555 14874 13893

0

5000

10000

15000

20000

25000

30000

Ba

se S

he

ar

(KN

)




8. Selvakoodalingam, B.; E. B. Perumal Pillai and P. Govindan (1999) Strengthening of RC Infilled frame with opening.

Concrete International.

9. Bureau of Indian Standards: IS-1893, part 1 (2002), “Criteria for Earthquake Resistant Design of Structures: Part 1

General provisions and Buildings”, New Delhi, India.

10. C.V.R Murty, Indian Institute of Technology Kanpur, Earthquake tips, India.

Books:

P. Agrawal, M. Shrikhande(2009) earthquake resistant design of structures (PHI Learning Pvt.Ltd. New delhi,

earthquake resistant design of low-rise open ground storey framed building … · 2017-04-07 ·...

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