Seismic Analysis and Design of Multistoried Building with and without Bracing According to is Code and Euro Code by using ETABS

Seismic Analysis and Design of Multistoried Building with and without Bracing According to is Code and Euro Code by using ETABS

D. Sirisha1

1Student, M Tech (SE), Department of Civil Engineering,

Aditya College of Engineering &Technology, Kakinada

M. Divya Tejaswi 2

2Assistant Professor, Department of Civil Engineering,

Aditya College of Engineering &Technology, Kakinada

Abstract: The construction of multistoried building with increased heights and with usage of light weight, high strength materials leads to flexible structures. Recent earthquakes implies that requirement to estimate the earthquake suitability of structures. Lateral stability is important for the steel structures in the seismic zone, effective way to increase the lateral strength is by means of bracing system. This paper deals with seismic analysis and design of multistoried (G+9)building with and without bracing according to IS code and EURO code by using ETABS 2015 software considering zone II and medium soil condition. The modeling and analysis of the structure have been done by Response Spectrum. The seismic performance of a structure with and without bracing configurations according to IS code and EURO code compared with respect to parameters like storey displacement ,storey drift and storey shear. Diagonal bracings are best bracing system for reducing the storey displacement because of increased stiffness and the structure is proposed to be designed by Limit state method.

Keywords: Bracing, ETABS 2015 Software, storey displacement, storey drift, storey shear, Response spectrum.

1. INTRODUCTION

   For newly constructed structures, Bracing is a system that utilizes a reinforced building structures. Bracing improves seismic performance of building. Braced frame structures are usually considered to resist the lateral forces and also earthquake loads. Braced systems provide due to their strength, stiffness to the structures.

   Under gravity load conditions, only beams and columns shall be considered to resist such loads, without taking bracing members into consideration. The diagonals shall be taken into account as follows in an elastic analysis of the structure for the seismic actions.

   Steel bracing is economical, easy to erect, occupies less space and has flexibility to design for meeting the required strength and stiffness. The advantages of braced buildings are due to bracing of the building, lateral storey displacement storey drift as well as axial force and bending moment in columns reduces to a remarkable level. Braced frame resist the wind and seismic forces, much more than non-braced buildings. Reduction in lateral displacement is a major advantage. Concentric bracing is more effective than the eccentric bracing. Concentrically braced frame are those in which the centerlines of members that meet at joint intersect at a same

   work point to form a vertical truss system that resist lateral forces.

   So overall purpose of bracing is to provide additional safety against the external loads in comparable self- building.

   Diagonal bracing can increase a building capability to withstand seismic activity. Bracing is important in earthquake resistant buildings because it helps keep a structure standing.

2. STRUCTURAL DETAILS OF MODEL

3. DIAGONAL BRACING

   Fig1: Diagonal Bracing

4. MODELLING AND METHODOLOGY

   In this paper we considered four types of models with and without bracing according to IS(Indian standard)code and EN(European )code and Diagonal bracing at storey 1 to 10 completely as shown in figures.

   Fig2: 3Dview of model1(G+9)multistoried bare frame building without bracing in IS code

   Fig3: 3D view of model2(G+9)multistoried bare frame building with bracing in IS code

   Fig4:3D view of model3(G+9)multistoried bare frame building without bracing in EN code

   Fig5:3Dview of model4 (G+9) multistoried bare frame building with bracing in EN code

5. DESIGN

1. Beam design:

   As per IS456:2000 by limit state method Grade of concrete fck=30N/mm2

   Grade of steel fy=500N/mm2 Clear span l=3.65mm

   Width of beam B=230mm

   Depth of beam D=420mm Clear cover=20mm

   Total load W=7.75 kN/m2 Factor load Wu=11.62 kN/m2 Ultimate moments:

   MX=6.76 kN-m MY=4.89kN-m

   Depth check: Mulim=62.63 kN-m

   Slab is safe against moment Ast= 126.53mm2

   Dia of bars=8mm

   Provide Spacing of 8mm# bars @ 300 mm c/c

   Effective depth d=395mm Clear cover=25mm Ultimate moment

   Mu=143.1kN-m (singly Reinforced beam) Provide Ast=402mm2

   Dia of bars =16mm No of bars=2 Deflection check=ok Shear force Vu=79kN Shear check=ok

   Provide Spacing 2 legged vertical stirrups16mm#bars at 296mm center to center

   Hence Beam is safe

2. Slab design:

   Size of slab=3.5×4.34m Ly/Lx=1.23<2

   Two way Slab

   Grade of concrete fck=30N/mm2 Grade of steel fy=500N/mm2 Overall Depth of slab D=150mm Effective depth d=125mm

   Shear force Vu=14.69 kN Shear check:

   Nominal shear stress v=Vu/bd = 0.118N/mm2 Design shear strength c=0.33N/mm2

   c max= 1.7N/mm2 v<c<c max

   Hence shear Reinforcement is not required.

3. Footings design:

   Size of column (lxb)=400x300mm Grade of concrete fck=30N/mm2 Grade of steel fy=500N/mm2

   Load Pu=800kN

   SBC of soil=200kN/m2 Area of footing A=4.4m2

   Size provided B=3m Soil Reaction qu=0.267N/mm2 Depth of footing:

   From shear consideration, IS456:2000

   Length between edge of footing to edge of column L=1.35m

   Critical shear stress c=0.32N/mm2 Depth d=600mm

   Overall depth D=650mm Bending moment: Mulim=216.4kN-m

   Two way shear:

   Critical section at d/2=300mm Perimeter of section p=3600mm Area of section a=2160000mm2 Upward pressure=985230N

   Two way shear stress=0.456N/mm2 Maximum shear=0.25fck=1.369N/mm2 Hence depth is sufficient

   Area of Reinforcement: In long direction :

   Moment Mu=364955625Nmm Ast=1436.51mm2

   Spacing Sv=180mm

   Provide Reinforcement of bars 16mm@180mm c/c In short direction:

   B=0.6m

   Moment Mu=144180000Nmm Ast=570.65mm2

   Spacing Sv=250mm

   Provide reinforcement of bars16mm@250mmc/c

4. column design:

Size of column=400x300mm Grade of concrete fck=30N/mm2 Grade of steel fy=500N/mm2 Pu=1200kN

Factored load=1800kN Mu=66.66kN

Factored Moment=100kN-m d|=50mm

d|/D = 50/500= 0.10

From IS 456, chart no36 y=0.36

x=0.04 PSC=0.4%

Asc=1000 mm2 No of bars=9

Provide transfer reinforcement of bars:8mm Pitch :

a)Least lateral dimension = 500

b)16 times the smallest diameter of the longitudinal reinforcement bar =16*12=192mm

c)300mm

Provide 8mm#@192mmc/c

6. RESULTS:

Table1: Storey Displacement with bracing

Displacement(mm)

Displacement(mm)

30

25

ShearKN

ShearKN

20

Grapp: Comparison of Storey Displacement with bracing

IS&EURO codes. 15

10

5

0

Model 4 shear storey(KN)E UROCODE

Model 2 shear storey (KN )IS CODE

0.000008

0.000006

0.000004

0.000002

0

Model 4

Drift EUROCODE

Model 2 Drift IS CODE

0.000008

0.000006

0.000004

0.000002

0

Model 4

Drift EUROCODE

Model 2 Drift IS CODE

Storey

Storey

Drift

Drift

Story10

Story8 Story6 Story4 Story2 Base

Story10

Story8 Story6 Story4 Story2 Base

Grapp: Comparison of Storey Drift with bracing IS&EURO codes.

Table3: Storey shear with bracing

Storey

Grapp: Comparison of storey shear with bracing IS&EURO codes.

Table4: Storey Displacement without bracing

Storey IS code EURO code

14000

12000

10000

8000

6000

4000

2000

0

Model 1

Displacement (mm)IS CODE

Model 3 Displacement(mm)E URO CODE

14000

12000

10000

8000

6000

4000

2000

0

Model 1

Displacement (mm)IS CODE

Model 3 Displacement(mm)E URO CODE

Storey

Storey

Displacement(mm)

Displacement(mm)

Story10

Story9 Story8 Story7 Story6 Story5 Story4 Story3 Story2 Story1 Base

Story10

Story9 Story8 Story7 Story6 Story5 Story4 Story3 Story2 Story1 Base

Graph4: Comparison of Storey Displacement without bracing IS&EURO codes.

Table5: Storey Drift without bracing

0.00018

0.00016

0.00014

0.00012

0.0001

0.00008

0.00006

0.00004

0.00002

0

Model 3 Drifts

EURO CODE

Model 1 Drifts

IS CODE

0.00018

0.00016

0.00014

0.00012

0.0001

0.00008

0.00006

0.00004

0.00002

0

Model 3 Drifts

EURO CODE

Model 1 Drifts

IS CODE

Storey

Storey

Drift

Drift

Grapp: Comparison of storey Drift without bracing IS&EURO codes.

Table6: Storey shear without bracing

0.004

0.0035

0.003

0.0025

0.002

0.0015

0.001

0.0005

0

Model 3

storyshear(KN)EU ROCODE

Model 1 storyshear(KN)ISC ODE

0.004

0.0035

0.003

0.0025

0.002

0.0015

0.001

0.0005

0

Model 3

storyshear(KN)EU ROCODE

Model 1 storyshear(KN)ISC ODE

Storey

Storey

Shear(KN)

Shear(KN)

Story10

Story9 Story8 Story7 Story6 Story5 Story4 Story3 Story2 Story1

Base

Story10

Story9 Story8 Story7 Story6 Story5 Story4 Story3 Story2 Story1

Base

Grapp: Comparison of storey shear without bracing IS&EURO codes.

CONCLUSION:

1. Bracings are the most critical members for the structure. To have a good control over the forces and displacements.

2. It is observed that the presence of bracing influences the overall behavior of structures when subjected to lateral displacements are reduced about 40%to89%in plan.

3. The presence of diagonal bracing subjected to storey displacement and storey drift are increased about 20% and base shear reduces to 60%

4. From present work it has been identified that storey drift of a structure with bracing is more compare to normal building.by providing bracing to a structure storey drift reduces to about 40%.

5. Storey drift are consideringly increased about 10to25%, base shear is consideringly reduced about 50%.than base shear is reduced when diagonal bracing is added to building.

6. It is observed that base shear is reduced to about 45%when compared to a building with bracing.

7. It is observed that by providing bracing at center of building, all parameters like base shear, lateral displacement and storey drift is consideringly reduced when compared to without bracing.

8. In Displacement EURO code is more compared to IS code in model 3&4

9. Drift is more occurring in storey 1in IS&EURO codes.

10. In EURO code displacement graph is randomly increase. Compare to IS code, so less displacement structure has more stiffness.

REFERENCES

1. Sachin Metre, shivanand Cghule, Ravikiran Comparative study of different types of bracing system by placing at different locations, International Research Journal of Engineering and Technology(IRJET),vol.4 Issue8,August 2017

2. Analysis and design of Multistorey structure using ETABS, International Research Journal of Engineering and Technology (IRJET), volume o4Issue may 2017.

3. IS456:2000 Indian Standard code of practice for plain and Reinforced concrete, Bureau of Indian Standards.

4. IS800:2007 Indian Standard code of practice for general construction in steel, Bureau of Indian Standards.

5. IS 875(Part I, II, and III) Indian Standard code of practice for design loads for buildings and structures.

6. IS1893 (Part1):2002 Earth quake Resistant Design of Structures, Part1 General Provisions and building, Bureau of Indian Standards.

7. Nagaraju and Shiva Kumar B.patil-Lateral Stability of high rise building with floating column, International Research Journal of Engineering and Technology(IRJET),volume2,Issue4,July2015

8. Krishnaraj, R.Chavan (2014) studied on Seismic Response of RC building with different arrangements of steel bracing system.

9. Zasiah Tafheem (2013) Studied on structural behaviour of steel building with concentric and eccentric bracing.

10. Mohammad Eyni Kangavar(2012) studied on seismic propensity of Knee Braced Frame(KBF) As Weighed against concentric Braced frame (CBF) utilizing ETABS and OPENSEES.

11. Pankaj Agarwal and Manish Shrikhande, Earthquake Resistant Design of Structures, Prentice.

12. N. Subramanian, Design of Reinforced Concrete Structure, Oxford University Press.