4th project persentetion

NAGPUR INSTITUTE OF TECHNOLOGY, NAGPUR(Department of civil engineering Session 2015-16)

4th

Project seminar on

“Parametric study of multi storied R.C.C flat slab structure under seismic effect having different plan aspect ratio and slenderness ratio.”

Submitted bySourabh Kumar Shubham Borkar

Under the guidanceProf. Sudhir Kapgate

• Aim• Objective• Introduction• Literature Survey• Structural Modeling• Result And Discussion• Conclusion• Future Scope• References

CONTENT

AIM

Parametric study of multi storied R.C.C flat slab structure under seismic effect having different plan aspect ratio and

slenderness ratio.

OBJECTIVE

• To perform parametric study on behaviour of multi storied R.C.C. flat slab structure having same plan area but different plan aspect ratio (L/B) and slenderness ratio (H/B), under seismic condition.

• To perform static and dynamic analysis using ETABS 15 software.

• To calculate and study the response of structure situated in seismic zone IV and their comparison.

• To determine limit aspect ratio and slenderness ratio for safe and stable structure.

INTRODUCTIONFLAT SLAB

A slab is a flat, two dimensional, planar structural element having thickness

small compared to its other two dimensions. It provides a working flat surface or

a covering shelter in buildings. It supports mainly transverse loads and transfers

them to support primarily by bending element just like flat plate. Hence in

warehouses, offices and public halls sometimes beams are avoided and slabs are

directly supported by columns. These types of construction are aesthetically

appealing also. These slabs which are directly supported by columns are called

Flat Slabs.COMPONENTS OF FLAT SLAB• Drops• Column Head • Column Strip• Middle Strip

SEISMIC ANALYSIS

• Earthquake is unpredictable and massive damage causing phenomena of nature.

• Deals with dynamic forces.

• Large forces hence can not design structure economically.

• Various BIS guidelines are available for analyze, design and detailing.

• Response spectrum method is used for analysis.

Building Configuration 1. It is one of the most important parameter for Earthquake Resistant structure.

Because a great deal of resistance is provided by the basic configuration and structural system of a building. The design of buildings for earthquake loads requires an early and close collaboration between the architect and engineer to arrive at the optimum structural design while still satisfying the functional and aesthetic needs of the client.

2. As per BIS guideline in IS 1893:2002 {Clause 7.1} says “Regular and Irregular Configuration to perform well in an earthquake, a building should possess four main attributes, namely simple and regular configuration, and adequate lateral strength, stiffness and ductility. Buildings having simple regular geometry and uniformly distributed mass and stiffness in plan as well as in elevation, suffer much less damage than buildings with irregular configurations”.

3. In IS 4326:1993 {Clause 4.4.1} it is mentioned that “The building should have a simple rectangular plan and be symmetrical both with respect to mass and rigidity so that the center of mass and rigidity of the building coincide with each other.” But the limiting “Plan aspect ratio” and “Slenderness ratio” for the regular structure is not prescribed.

4. Due to inadequate space available at important location of city, high land rates and for economical utilization of space architects and engineers are planning and constructing such buildings which are having larger aspect ratio and higher slenderness ratio. The buildings, especially of

institutional or commercial use are having lager plan aspect ratio and slenderness ratio.

With this background it is found essential to study the behaviour of buildings having large aspect ratio and slenderness ratio under seismic condition to predict maximum losses would occur and control measures to be taken to overcome this problem. This is the primary motivation underlying the present study

LITERATURE SURVEY1. Rucha S. Banginwar and M. R. Vyawahare, (2012) “Effect of Plans Configurations on the Seismic Behaviour of the Structure By Response Spectrum Method”The study is carried on the effect of different geometrical configurations on the behaviour of structure of the already constructed building located in the same area during earthquake by Response spectrum method (RSM) in this paper, more emphasis is made on the plan configurations and is analysed by RSM since the RSM analysis provides key information for real – world application. In the present study the response (i.e. behaviour) of already constructed three buildings of college which are having different building geometric configuration in plan has been studied with the help of response spectrum method and at the end out of these three buildings, vulnerable building has been detected.The conclusions of this study are briefly described as follows: • The plan configurations of structure have substantial impact on the seismic

response of structure in terms of lateral deformation and storey shear. • Effect of area on Storey shear; it was observed that the storey shear in ‘T’ shape

building was more though the irregularity in the plan configuration was less as compared to ‘V’ shaped building.

• Torsion- Torsion was observed only in ‘V’ shaped building as the level of irregularity is maximum. The building is symmetrical about one axis but the orientation of block is oblique.

• Displacement – Large displacement were observed in the ‘V’ shape building and least displacement were observed in rectangular building. It indicates that building with severe irregularity shows maximum displacement and storey drift.

2. K S Sable (2012), “Comparative Study of Seismic Behaviour of Multi-storey Flat Slab and Conventional Reinforced Concrete Framed Structures”This paper presents a summary of the study, for conventional R.C.C framed structure building and flat slab building for different floor height. The effect of seismic load has been studied for the two types of building by changing overall height of structure. On the basis of the results obtained in this study, following conclusions have been drawn: • The natural time period increases as the height of building ( No. of stories)

increases, irrespective of type of building viz. conventional structure, flat slab structure and flat slab with shear wall. However, the time period is same for flat slab structure and flat slab with shear wall.

• In comparison of the conventional R.C.C. building to flat slab building, the time period is more for conventional building than flat slab building because of monolithic construction.

• For all the structure, base shear increases as the height increases. This increase in base shear is gradual up to 9th storey, thereafter, it increases significantly gives rise to further investigation on the topic.

• Base shear of conventional R.C.C building is less than the flat slab building. • Storey drift in buildings with flat slab construction is considerably more as

compared to conventional R.C.C building. This influences moment which is developed during earthquake. In flat slab construction additional moments are developed. Thus, the columns of such buildings should be designed by considering additional moment caused by the Storey drift.

• A structure with a large degree of indeterminacy is superior to one with less indeterminacy, this is primarily because of more members are monolithically connected to each other and if yielding takes place in any one of them, then a redistribution of forces takes place. As a result, the structure can sustain to take additional load. Additionally, redistribution reduces as the number of member reduces in a selected lateral load resisting system

3. Arun Solomon (2013) “Limitation of irregular structure for seismic response”In this study, non-linear behavior of irregular structures. Because of the limitations of available size and shape of land for construction of buildings some of the structures become highly irregular as too long and too tall. The intension of this study was to identify the limitations of the too long and too tall structures using the software SAP 2000.Author’s aim was to show structure having regular building configuration behaves like irregular structure when it is too long and too tall regular structure by performing non-linear analysis (Pushover analysis).From the investigation on the two types of too long structures the following results are obtained. The aspect ratio of the building is 1. Type I Building aspect Ratio (85/15) = 5.66. 2. Type II Building aspect Ratio (145/25) = 5.8 Author has concluded that • The too long structures does not meet the performance limit if one of the plan

dimension of the structure go beyond 5.6 times of another dimension, the building. Hence such types of too long buildings should be avoided while constructing in earthquake prone areas.

• From the study on too tall structure the subsequent result is obtained by author. If thr slenderness ratio of the building is (92/15) = 6.13 then a too tall structure does not meet the performance limit if the structure’s slenderness ratio exceeds 6.13.

STRUCTURAL MODELING

Modeling a structure involves the modeling and assemblage of its various load-carrying elements. The model must ideally represent the mass distribution, strength, stiffness and deformability. Modeling and analysis is done with the help of ETABS 15 software. All 25 structures are separately modeled and analyzed by RSM. Template available for flat slab with drop are used to create models in ETABS software, proper material properties and joint restrains are assigned and column are assigned fixed support at base. Slabs and drops are assigned as Diaphragms which resist in plane deflection. Following table represents all 25 models classified in different groups and named accordingly.

Sr.No Model Group Model Aspect

Ratio Length

(m) Width(m)

Column Spacing

(m)

No. Of Storey

Storey Height

(m)

Slenderness Ratio

(L:B) L B X Z 3.60 (H:B)1

M1

M11

1 30 30 6 6

3 14.40 0.482 M12 5 21.60 0.723 M13 7 28.80 0.964 M14 9 36.00 1.25 M15 11 43.20 1.446

M2

M21

2 41 22 5.85 5.5

3 14.40 0.697 M22 5 21.60 1.038 M23 7 28.80 1.379 M24 9 36.00 1.71

10 M25 11 43.20 2.0611

M3

M31

3 50 18 5 6

3 14.40 0.8512 M32 5 21.60 1.2713 M33 7 28.80 1.6914 M34 9 36.00 2.1215 M35 11 43.20 2.5416

M4

M41

4 60 15 6 5

3 14.40 0.9617 M42 5 21.60 1.4418 M43 7 28.80 1.9219 M44 9 36.00 2.420 M45 11 43.20 2.8821

M5

M51

5 75 12 6.25 6

3 14.40 1.1122 M52 5 21.60 1.6623 M53 7 28.80 2.2224 M54 9 36.00 2.7725 M55 11 43.20 3.32

Sr.

No.Design Parameter Value

1 Unit weight of concrete 25 kN/m3

2 Characteristic strength of concrete 30 MPa

3 Characteristic strength of steel 415 MPa

4 Modulus of elasticity of steel 2 x 105 MPa

5 Plan area 900 square meters

6 Slab thickness 200 mm

7 Drop thickness 300 mm

8 Depth of foundation 3.5m

9 Floor height 3.6m

MATERIAL PROPERTIES AND GEOMETRIC PARAMETERS

Sr.No. Design Parameter Value

1 Earthquake Load As Per IS 1893 (Part 1)-2002

2 Type Of Foundation Isolated Column Footing

3 Depth Of Foundation 3.5m

4 Type Of Soil Type II, Medium As Per IS 1893:2002

5 Bearing Capacity Of Soil 200 kN/m2

6 Seismic Zone IV

7 Zone factor (Z) 0.24

8 Response reduction factor (R) 5

9 Importance Factor 1

10 Percentage Damping 5%

11 Type Of Frame Special Moment Resisting Frame

SEISMIC DESIGN DATA

LOAD CONSIDERED FOR ANALYSIS OF BUILDING

Sr.No. Load Type Value

1 Self-weight of Slab and ColumnAs per Dimension and Unit

weight of concrete

2 Dead load of structural components As per IS 875 Part-1

3 Live Load As per IS 875 Part -2

4 Live load : on Roof and Typical floor 4.0 kN/m2

5 Floor Finish 2.0 kN/m2

CROSS SECTIONAL DIMENSION FOR COLUMN

Sr. No. Type of Structure Column sizes

1 G+ 3 (5 storey structure) 450 mm X 450 mm

2 G+ 5 (7 Storey structure) 450 mm X 450 mm




BASE SHEAR (VB)

Design codes represent the earthquake-induced inertia forces as the net effect of such

random shaking in the form of design equivalent static lateral force.

Base Shear is total design lateral force at the base of structure. So, base shear is nothing but

the maximum expected lateral force that will occur due to seismic ground motion at the

base of a structure.

MAXIMUM STOREY DRIFT

Drift is the lateral movement of a building under the influence of earthquake induced

vibrations. Storey drift is the lateral displacement of one level relative to the level above or

below. It can also be defined as the drift of one level of a multistorey building relative to

the level below. It is difference between lateral displacements of adjacent storey.

NATURAL PERIOD

Natural Period (Tn) of a building is the time taken by it to undergo one complete cycle of

oscillation. It is an inherent property of a building controlled by its mass m and stiffness k.

Its units are seconds (s). Thus, buildings that are heavy (with larger mass m) and flexible

(with smaller stiffness k) have larger natural period than light and stiff buildings.

NATURAL FREQUENCY

The reciprocal (1/Tn) of natural period of a building is called the Natural Frequency fn; its

unit is Hertz (Hz). The building offers least resistance when shaken at its natural frequency

(or natural period).

RESULT AND DISCUSSIONPARAMETER FOR COMPARATIVE STUDY

Following parameters are considered for comparative study of analysis results of all 25 models.• Base shear• Storey drift• Storey stiffness• Maximum storey displacement • Natural time period Results obtained from software analysis of all 25 models were filtered and then arranged to compare it with respective values of other models. For better understanding of results graphs are plotted.

RESULTS FOR MODEL M11SN STOREY Shear X Drift X Stiffness

XShear Y Drift Y Stiffness Y Displacement

XDisplacement

YkN Mm kN/m kN Mm kN/m mm mm

1 2 3 4 5 6 7 8 91 STOREY5 1029.721 3.8 274140.2 1029.721 3.8 274140.2 28.7 28.7

2 STOREY4 1595.299 5.8 274828.4 1595.299 5.8 274828.4 25.6 25.6

3 STOREY3 1962.43 7.3 270623 1962.43 7.3 270623 20.4 20.4

4 STOREY2 2311.962 8.1 286026.4 2311.962 8.1 286026.4 13.5 13.5

5 STOREY1 2583.759 5.4 475483.2 2583.759 5.4 475483.2 5.4 5.4

6 BASE 0 0

RESULTS FOR MODEL M21SN STOREY Shear X Drift X Stiffness


XDisplacement

YkN Mm kN/m kN mm kN/m mm mm

1 2 3 4 5 6 7 8 91 STOREY5

1031.403 3.4 302630.2 1022.38 3.3 312406.5 26.5 25.5

2 STOREY41618.888 5.3 303751.8 1614.999 5.1 315708.7 23.7 22.8

3 STOREY32009.261 6.7 299344.3 2010.987 6.4 312635.9 18.9 18.2

4 STOREY22367.846 7.5 316271.8 2370.341 7.2 330083.3 12.4 12

5 STOREY12635.777 5 525762.1 2635.779 4.9 541599.8 5 4.9

6 BASE 0 0

Results for model M31SN STOREY Shear X Drift X Stiffness


XDisplacement


1 2 3 4 5 6 7 8 91 STOREY5

1035.748 3.2 320199.7 1048.994 3.5 302434.6 25.6 26.7

2 STOREY41640.546 5.1 321193.3 1646.386 5.4 306086.5 22.9 23.8

3 STOREY32045.088 6.5 316728.9 2041.164 6.7 302978.8 18.3 19

4 STOREY22410.73 7.2 333205.4 2406.145 7.5 320973.6 12.1 12.5

5 STOREY12680.553 4.9 545329.7 2680.553 5 532491.7 4.9 5

6 BASE 0 0



XDisplacement


1 2 3 4 5 6 7 8 91 STOREY5

1061.909 3.6 295525.2 1033.535 3.2 325995.6 27.7 24.7

2 STOREY41656.292 5.6 295899.6 1643.993 4.9 332708.6 24.8 22

3 STOREY32046.92 7 290892.1 2052.612 6.2 331574.2 19.7 17.6

4 STOREY22412.306 7.8 307906.7 2420.332 6.9 350073.1 13 11.6

5 STOREY12690.351 5.2 517051.7 2690.352 4.8 565040.2 5.2 4.8

6 BASE 0 0



XDisplacement


1 2 3 4 5 6 7 8 91 STOREY5 1076.337 4.2 253617.5 1053.084 3.9 272967.9 31.6 29.1

2 STOREY4 1638.553 6.5 252628.1 1628.855 5.9 275226.1 28.2 26

3 STOREY3 1993.066 8.1 247292 1999.221 7.4 271845.6 22.5 20.7

4 STOREY22347.955 8.9 262573.4 2355.789 8.2 287630.2 14.8 13.7

5 STOREY1 2636.396 5.9 447252.8 2636.39 5.5 476117.9 5.9 5.5

6 BASE 0 0

SN Mode Period Frequency

Period Frequency

Period Frequency Period Frequency

Period Frequency

sec cyc/sec sec cyc/sec sec cyc/sec sec cyc/sec sec cyc/sec M11 M21 M31 M41 M51

1 1 1.561 0.641 1.488 0.672 1.492 0.67 1.523 0.657 1.523 0.6572 2 1.551 0.645 1.459 0.685 1.462 0.684 1.434 0.697 1.434 0.6973 3 1.438 0.695 1.374 0.728 1.42 0.704 1.384 0.722 1.384 0.7224 4 0.495 2.02 0.473 2.116 0.474 2.111 0.482 2.073 0.482 2.0735 5 0.493 2.03 0.465 2.152 0.466 2.146 0.458 2.183 0.458 2.1836 6 0.453 2.209 0.434 2.303 0.449 2.229 0.44 2.275 0.44 2.2757 7 0.276 3.622 0.264 3.788 0.265 3.779 0.269 3.724 0.269 3.7248 8 0.275 3.634 0.261 3.837 0.262 3.816 0.258 3.87 0.258 3.879 9 0.249 4.011 0.241 4.158 0.248 4.027 0.245 4.077 0.245 4.077

10 10 0.187 5.335 0.179 5.572 0.18 5.547 0.182 5.503 0.182 5.50311 11 0.187 5.344 0.178 5.607 0.179 5.574 0.178 5.607 0.178 5.60712 12 0.167 5.999 0.162 6.175 0.167 5.98 0.167 5.989 0.167 5.989

Variation in period and frequency

RESULTS FOR MAXIMUM DIFLECTION

0 5 10 15 20 25 30 350

1

2

3

4

5

6

Displacement in X

m11m21m31m41m51

Displacement in mm

store

y

0 5 10 15 20 25 30 350

1

2

3

4

5

6

0

1

2

3

4

5

0

1

2

3

4

5

0

1

2

3

4

5

0

1

2

3

4

5

0

1

2

3

4

5

Displacement in y

m11m21m31m41m51

Displacement in mm

NO O

F ST

ORY

FOR G+3 STOREY

FOR G+5 STOREY

0 10 20 30 40 50 600

1

2

3

4

5

6

7

8

Displacement in X

m12m22m32m42m52

Displacement in X (mm)

No o

f Sto

ry

0 5 10 15 20 25 30 35 40 45 500

1

2

3

4

5

6

7

8

Displacement in y

m12m22m32m42m52

Displacement in Y (mm)

No o

f Sto

ry

FOR G+7 STOREY

0 10 20 30 40 50 60 700123456789

10

Displacement in X

M13M23M33M43M53

Displacements IN X (mm)

Stor

ey

0 10 20 30 40 50 60 700123456789

10

Displacement in y

M13M23M33M43M53

Displacements Y (mm)

Stor

ey

FOR G+9 STOREY

0 10 20 30 40 50 60 70 800

2

4

6

8

10

12

Displacement in X

M14M24M34M44M54

Displacements mm

Stor

ey

0 10 20 30 40 50 60 700

2

4

6

8

10

12

Displacement in Y

M14M24M34M44M54

Displacements mm

Stor

ey

0 20 40 60 80 100 120 1400

2

4

6

8

10

12

14

Displacements in X

M15M25M35M45M55

Displacements in X mm

stor

ey

0 20 40 60 80 100 120 140 160 180 2000

2

4

6

8

10

12

14

Displacements in Y

M15M25M35M45M55

Displacement in y (mm)

stor

ey

FOR G+11 STOREY

OBSERVATION

From above graphs points observed are as following

• Displacement for aspect ratio L/B = 5 is maximum.

• For first mode displacement in x direction is greater than y direction up to G+9

models.

• Displacement decreases with increase in aspect ratio up to L/B = 3.

RESULTS FOR MAXIMUM STOREY DRIFTFOR G+3 STOREY

0.0005 0.001 0.0015 0.002 0.0025 0.0030123456

Drift in X

m11m21m31m41m51

Drift in x (m)

No

of S

tore

y

0.0005 0.001 0.0015 0.002 0.0025 0.0030123456

Drift in Y

m11m21m31m41m51

Drift in x (m)

No

of S

tore

y

FOR G+3 STOREY

0.0005 0.001 0.0015 0.002 0.0025 0.0030

1

2

3

4

5

6

7

8

Drift in X

m12m22m32m42m52

Drift in m

No o

f Sto

rey

0.0005 0.001 0.0015 0.002 0.0025 0.0030

1

2

3

4

5

6

7

8

Drift in Y

m12m22m32m42m52

Drift in m

No o

f Sto

rey

FOR G+7 STOREY

2 3 4 5 6 7 8 9 10 110123456789

10

Drift X

M13M23M33M43M53

Drift X

Stor

ey

2 3 4 5 6 7 8 9 10 110123456789

10

Drift Y

M13M23M33M43M53

Drift Y

Stor

ey

FOR G+9 STOREY

2 3 4 5 6 7 8 9 100

2

4

6

8

10

12

Drift X

M14M24M34M44M54

Drift X

Stor

y

2 3 4 5 6 7 8 90

2

4

6

8

10

12

Drift Y

M14M24M34M44M54

Drift Y

Stor

y

FOR G+9 STOREY

0 2 4 6 8 10 12 14 160

2

4

6

8

10

12

14

Drift X

M15M25M35M45M55

Drift X

Stor

y

0 5 10 15 20 250

2

4

6

8

10

12

14

Drift Y

M15M25M35M45M55

Drift Y

Stor

y

From above graphs points observed are as following• In case of flat slab structure Storey drift in x direction is more as compared to Storey drift

in y direction for same slenderness ratio.• Maximum value of Storey drift was found out to be at second storey level in case of G+3,

G+5, G+7 structures where as in case of G+9 and G+11 storey structure the maximum Storey drift was found on third storey level

• As per limitation laid by IS 1893 (Part 1) 2002, the maximum drift should not be more than 0.004 times storey height which is 0.0144 m. This drift limit is exceeds in aspect ratio L/B= 5 and slenderness ratio 3.32

OBSERVATION

200000 250000 300000 350000 400000 450000 500000 550000 6000000

1

2

3

4

5

6

stiffness in x direction

M11M21M31M41M51

STIFFNESS IN X

STO

REY

250000 300000 350000 400000 450000 500000 550000 6000000

1

2

3

4

5

6


M11M21M31M41M51

STIFFNESS IN Y

STO

REY

200000 250000 300000 350000 400000 450000 500000 550000 6000000

1

2

3

4

5

6

7

8


m12m22m32m42m52

Stiffness X

Stor

y

2000002500003000003500004000004500005000005500006000000

1

2

3

4

5

6

7

8

Stiffness Y

m12m22m32m42m52

Stiffness YStiffness Y

Stor

y

RESULTS FOR STOREY STIFFNESSFOR G+3 STOREY

FOR G+5 STOREY

FOR G+7 STOREY

200000 250000 300000 350000 400000 450000 500000 5500000123456789

10

Stiffness X

M13M23M33M43M53

Stiffness X

Stor

y

200000 250000 300000 350000 400000 450000 500000 550000 6000000123456789

10

Stiffness Y

M13M23M33M43M53

Stiffness Y

Stor

y

FOR G+9 STOREY

200000

300000

400000

500000

600000

700000

800000

900000

1000000

11000000

2

4

6

8

10

12

G+9

M14M24M34M44M54

Stiffness X

Stor

y

200000

300000

400000

500000

600000

700000

800000

900000

1000000

11000000

2

4

6

8

10

12

G+9

M14M24M34M44M54

Stiffness Y

Stor

y

FOR G+11 STOREY

100000

200000

300000

400000

500000

600000

700000

800000

900000

10000000

2

4

6

8

10

12

14

Story Stiffness X

M15M25M35M45M55

Story Stiffness

Stor

y

0 200000 400000 600000 800000 1000000 12000000

2

4

6

8

10

12

14

Story Stiffness Y

M15M25M35M45M55

Story Stiffness

Stor

y

OBSERVATION

From above graphs points observed are as following• Storey stiffness increases with size of column• For same size of column stiffness increases with no of column in respective direction

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.80

2

4

6

8

10

12

14

G+3

M11M21M31M41M51

Period

Mod

e

0 0.5 1 1.5 2 2.50

2

4

6

8

10

12

14

G+3

m12m22m32m42m52

Period

Mod

e

0 0.5 1 1.5 2 2.5 3 3.50

2

4

6

8

10

12

14

G+7

M13M23M33M43M53

Period

Mod

e

0 0.5 1 1.5 2 2.5 3 3.50

2

4

6

8

10

12

14

G+9

m14m24m34m44m54

Period sec

Mod

e

0 1 2 3 4 5 60

2

4

6

8

10

12

14

G+11

M15M25M35M45M55

Period

Mod

e

OBSERVATION

From above graphs points observed are as following• For first 3 modes value of time period is maximum.• With increase in no of storey time period increases.• Sudden increase in time period for model M55 is noted.

RESULTS BASE SHEAR

• From tables of results the value of the base shear is found out to be increasing with

increase in slenderness ratio & aspect ratio.

• The percentage increase in base shear for aspect ratio 4 & 5 is more as compared to other

ratio, as the column size increases seismic weight increases.

• In case of same number of storey base shear does not increases linearly with linear

increase in aspect ratio. STOREY DRIFT

• Building with aspect ratio 1 have same drift in both the direction

• Increase in slenderness ratio Results in increasing maximum storey drift

• In case of flat slab structure Storey drift in x direction is more as compared to Storey drift

in y direction for same slenderness ratio

• Maximum value of Storey drift was found out to be at second storey level in case of G+3,

G+5, G+7 structures where as in case of G+9 and G+11 storey structure the maximum

Storey drift was found on third storey level .

• Value of maximum storey drift is exceeded in model M55 is 20.1 mm which is more than

limiting value 14.4 mm for storey height 3600 mm.

• Increasing lateral stiffness of structure by increasing size of column results in increasing

storey level of maximum storey drift.

• As per limitation laid by IS 1893 (Part 1) 2002, the maximum drift should not be more

than 0.004 times storey height which is 0.0144 m. This drift limit is exceeds in aspect ratio

L/B= 5 and slenderness ratio 3.32.

STIFFNESS

• With increase in lateral storey Stiffness fundamental time period decreases.

• Increase in lateral storey stiffness Results in decreases Storey drift and maximum storey

displacement.

• In same aspect ratio size of column are not fixed so stiffness changes with change in

column size. Results in change of behaviour of structure for lateral loading.

• Increasing lateral stiffness of structure by increasing size of column results in increasing

storey level of maximum storey drift.

NATURAL TIME PERIOD

• The value of time period increases with increase in slenderness ratio

• The numerical value for modal period and frequency shows that value of period

increases linearly with linear increase in slenderness ratio but not in the case of change

in aspect ratio.

• First three modes of displacement governs the response of structure for lateral loads. In

first three modes natural time period is more frequency is less hence for lower values

of excitation gives maximum lateral deflection.

Based on the work done in this dissertation following conclusions are drawn:

Limiting plan aspect ratio is L/B =5 and slenderness ratio is 3.32.

Structure with aspect ratio more than 3 has higher magnitude of design base shear

along both X and Y direction though their seismic weight is lesser than structure

with aspect ratio 3.

Curtailment in column size reduces the seismic weight of structure, hence less

seismic weigh and less base shear.

Buildings having square plan shape i.e. aspect ratio 1, is safest because:• Lower and equal amount of base shear is acting along both X and Y

direction.• Fundamental time period for square plan structure is comparatively lesser

than rectangular plan building. Hence it will perform well during earthquake with higher frequencies.

• Lateral deformation (i.e. lateral displacement and storey drift) for all the storey level is same along both X and Y direction.

CONCLUSION

FUTURE SCOPE • Present study is strictly restricted to effect of seismic forces on flat slab structure

without any lateral force resisting infill elements. To acquire in-depth knowledge about

structural behaviour we need to study structure with infill element which resist the

lateral displacement of structure or which does not resist the movement.

• Types of damage occur and points of critical damage are to be studied to save

unrepairable damage to lives of animals and human kind and other economic, strategic

losses.

• Behaviour of flat slab structure with different structural bracing elements under lateral

loads are to be found out.

• Prof. K S Sable, Er. V A Ghodechor, Prof. S B Kandekar, “Comparative Study of Seismic Behavior of Multistory Flat Slab and Conventional Reinforced Concrete Framed Structures”, International Journal of Computer Technology and Electronics Engineering (IJCTEE) Volume 2, Issue 3, June 2012

• Rucha.S.Banginwar, M.R.Vyawahare, P.O.Modani, “Effect of Plan Configurations on the Seismic Behavior of the structure By Response Spectrum Method” ,International Journal of Engineering Research and Applications(IJERA),Vol2,May-June2012

• Arun Solomon A, Hemalatha G, “Limitation of irregular structure for seismic response”, International Journal Of Civil And Structural Engineering Volume 3, No 3, 2013

• Mohit Sharma and Dr. Savita Maru(2014), “Dynamic Analysis of Multistoried Regular Building” , Journal of Mechanical and Civil Engineering (IOSR-JMCE), Volume 11, Issue 1 Ver. II.

• Mayuri D. Bhagwat and Dr.P.S.Patil(2014), “Comparative study of performance of rcc multistory building for Koyna and Bhuj earthquakes”, International Journal of Advanced Technology in Engineering and Science Volume No.02, Issue No. 07.

• Dr. V.L. Shah and Late Dr. S.R. Karve, “Illustrated design of reinforced concrete buildings”, Sixth edition, Structures publications, 36 Parvati, Pune-411009.

REFERENCES

• Paz. Mario. “Structural Dynamics" theory and Computation, CBS, Publishers and Distributors Dayaganj, New Delhi.

• C. V. R. Murty, Rupen Goswami, A. R. Vijayanarayanan and Vipul V. Mehta, “Some Concepts in Earthquake Behaviour of Buildings”, Gujarat State Disaster Management Authority Government of Gujarat.

• BIS-1893, Criteria for Earthquake resistant design of structures-Part-1, General Provisions and Buildings, Bureau of Indian Standards, New Delhi -2002.

• I.S-13920."Ductile detailing of reinforced structures subjected to seismic force" code of practice Bureau of Indian Standards, New Delhi -1993.

• I.S. 456-2000, Indian Standard Code of Practice for Plain and Reinforced Concrete, Bureau of Indian Standard, New Delhi.

• IS-875-1987.".Indian standard code of practice for structural safety loadings standards Part-1, 2" Bureau of Indian Standards, New Delhi.

• I.S 4326 – 1993, Earthquake Resistant Design And Construction Of Buildings - Code Of Practice, Bureau of Indian Standard, New Delhi

• SP-16-1980- Design Aids for Reinforced concrete to IS-456-1978-Bureau of Indian Standards, New Delhi.

• SP 22 : 1982 Explanatory Handbook On Codes For Earthquake Engineering, Bureau Of Indian Standard, New Delhi

• www.nicee.org, The National Information Centre of Earthquake Engineering (NICEE - established 1999)

THANK YOU