design, structural analysis and performance investigation ... · key words: floating columns, high...

DESIGN, STRUCTURAL ANALYSIS AND PERFORMANCE

INVESTIGATION ON STATIC SEISMIC ANALYSIS OF G+10 MULTI

STOREYSTRUCTURES WITH AND WITHOUT FLOATING COLUMN -

A COMPARATIVE STUDY

Chandan Kumar1, G. Ragul

2, V.Jayakumar

3, Prasidh E Prakash

4

1Department of Civil Engineering, Budge Budge Institute of Technology, Kolkata, India

[email protected]

2Department of Mechanical Engineering, Budge Budge Institute of Technology, Kolkata, India

[email protected] 3Department of Mechanical Engineering, Saveetha School of Engineering, Saveetha University, India

[email protected] 4 Department of Mechanical Engineering, Malabar College of Engineering and Technology, Kerala, India

[email protected]

Abstract

In recent time, there is a huge revolution in construction industry and lack of horizontal space in

urban areas of India. Architects and structural engineers have developed many innovative

techniques to occupy the vertical space by constructing tall structure. Also the demand for more

open space in ground and upper story has increased in past decade. To overcome this, a

technique called floating column is adopted in multistory structures.

In this research work an attempt is made tostudies the behavior of G+10 multistorey structures

with floating column and without floating column by static seismic analysis. To study the forces

in columns exterior, interior and core columns are grouped and Parameters such as story drifts,

story displacement, and Base shear were compared to get economic design in seismic prone

areas. Design and Analysis was carried out by using STAAD PRO V8i 2016 Software.

Key words: Floating Columns, High-rise buildings, seismic analysis, STAAD PRO V8i, Base

shear.

1. Introduction

Shrikanth .M.K et.al, [1] studied the behaviour of G+5 story structure with and without floating

column for parameters such as drift and displacement of the building by SAP 2000v17

software.Priyankakumari, N.r.Dhamge, [2] have done the linear dynamic analysis of floating

column structure and comparison of axial load, displacement, moment and shear in four different

International Journal of Pure and Applied MathematicsVolume 119 No. 16 2018, 805-819ISSN: 1314-3395 (on-line version)url: http://www.acadpubl.eu/hub/Special Issue http://www.acadpubl.eu/hub/

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seismic zones.T.Raja. Sekhar, P.V.Prasad, [3] studied the behavior of framed building by using

time history analysis on a 3D model which was on floating and non-floating column structure

and put forward the relationship between the behavior of structure in different seismic zones of

india and studied the various parameters such as base shear, displacement ect.,PrernaNautiyal,

Saleem Akhtar and GeetaBatham, [4] investigated on the behavior of floating column structure

for different soil excitations(different types of soil) and to get the idea of safety factor as there is

no provision for magnification factor in any IS code.Shiwliroy, GargiDanda de [5] investigated

the behavior of different story structures with floating column and studied the bending moment,

shear force variation at different levels for various structure G+3, G+5, G+10.

SreekanthGandlaNanabala, Pradeep Kumar Ramancharla, Arunakanthi E, [6] studied the time

history analysis on two types of structure one with G+5 non floating column and another G+5

floating column structure for different time history data from past and compared the behavior of

two structure to get an idea for an economic design in seismic prone areas. NiteenMalu,

Amaresh.S.Patil, [7] studied the behavior of various g+10 structure with pushover analysis in

seismic prone areas by ETABS software and compared the base shear, story shear response of

the structure.

Fig.1Floating column load path

2. Analysis of structure

The analysis is carried out for the effect of floating columns in lateral performance of a

symmetrical shape G+10 story building for the following Structures.

CASE1: RC Building without floating column.

CASE2: RC Building with floating column at ground floor in central level.

2.1 Basic data

RC Building and floating column building.

1. No of stories : 10 stories

2. Roof height : 28Mts

3. Slab thickness : 125mm

4. Grade of concrete : Grade 35

5. Grade of steel : Fe500

6. Storey Height : 3.5m

7. Column spacing : 6.00m

8. Outer and Inner Columns : up to 10th

floor = 1.50 x 1.50m

9. Perimeter Framing beam size : 230 x 600mm

10. All other Beams : 230 x 600 mm.

3. Loads on the structure

International Journal of Pure and Applied Mathematics Special Issue

806

3.1 Live Load

Live load is assumed as per IS 875(part 2-imposed loads) table 1.

Since the building is assumed to be an office building the live load was taken 3 kN/m², (office

buildings with no separate storage)all floors. These slab panels are assumed to behave as a rigid

diaphragm.

3.2 SUPER IMPOSED DEAD LOADS (S.D.L.)

3.2.1 Floor Load:

A floor load of 1 kN/m² is applied on all the slab panels on all the floors for the floor finishes and

the other things.

3.2.2 Member Load:

A UDL of 3kN/m is considered on inner beams and 6kN/m is considered on perimeter beams for

the wall load considering the wall to be made of Light Weight Bricks.

3.3 Wind load

Wind load in this study is established in accordance with IS 875(part 3-Wind loads).

The Basic wind speed as per the code is Vb=44m/s.

The coefficients K1 and K2 are taken as 1.0.

The terrain category is taken as „Category 4‟ with structure class C.

Taking internal pressure coefficient as ±0.2 the net pressure coefficient Cp (windward) works out

as +0.8 and Cp (leeward) as -0.5 based on h/w and l/w ratio of table 4 of IS 875 (part3).

3.4 Earthquake Loads

Earthquake load in this study is established in accordance with IS 1893(part 1)-2002.

The city of Hyderabad falls in “zone 2”.

Hence Zone factor Z=0.10.

The response reduction factor R is taken as 3.0 for all frames.

Ta = 0.075*h0.75

VB = Ah* W.

Qi = VB * (Wi*hi2)*(∑Wj*hj

2)-1

The structure is analyzed as per the loading combinations provided in IS: 456-2000.

The behaviors of 6 columns are studied as given below:

C1 - exterior center column

C2 - exterior penultimate column

C3 - exterior corner column

C4 - interior center column

C5 - interior corner column

C6 - core column

4. PLAN AND ISOMETRIC VIEWS OF THE STRUCTURE:


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Fig.2 Centerline plan of both normal Fig.3 floating column Structure

Fig.4 Isometric View of floating column Structure

Fig.5 Front View of floating column Structure

Fig.7 Isometric view of Structure without floating column


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Fig.8 Isometric view of Structure with floating column at ground level

Fig.9 Central section of Structure with floating column at ground level and first floor level

Fig.10 Isometric view of Structure with floating column at ground level and first floor level

Fig.11 Top view of the structure


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5. Result and discussions

5.1 Drift and displacement

The most significant basic parameter monitored throughout the whole analysis process was Drift

and Displacement at the top story of the building. The following shows the displacement & drift

as follows:

5.2 Graphs for column displacement for floating column and normal building

Fig.12 Column displacement for floating column and normal building inX-direction

Fig.13 Column displacement for floating column and normal building inY-direction

0

2

4

6

8

10

12

0 50 100 150

disp x

disp x

0

2

4

6

8

10

12

-4 -2 0 2

disp y

disp y


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Fig.14 Column displacement for floating column and normal building inZ-direction

5.3 Column Axial Forces

The structural scheme analyzed in the present study is activated once the outriggers are

engaged and transfer the core bending moment to the outboard column as a couple of axial

forces.

Columns considered for comparison of Analysis are C1, C2, C3, C4, C5, and C6

5.4 Graphs for column axial force for floating column and normal building compression

Fig.15 Column axial force for floating column and normal building compression in Px-direction

0

2

4

6

8

10

12

0 50 100 150

disp Z

disp Z

-2000

0

2000

4000

6000

8000

10000

0 10 20 30

FLOATING COLUMN

WITH COLUMN


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Fig.16 Column axial force for floating column and normal building compression in Py-direction

Fig.17 Column axial force for floating column and normal building compression in Pz-direction

Fig.18 Column axial force for floating column and normal building compression in Mx-direction

-1000

0

10002000

30004000

5000

60007000

8000

900010000

0 10 20 30

FLOATING COLUMN

WITH COLUMN

0

50

100

150

200

250

0 10 20 30

FLOATING COLUMN

WITH COLUMN

0

100

200

300

400

500

600

0 10 20 30

FLOATING COLUMN

WITH COLUMN


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Fig.19 Column axial force for floating column and normal building compression in My-direction

Fig.20 Column axial force for floating column and normal building compression in Mz

Storey drift

Another very important factor that is monitored is the storey drift along the height of the buiding.

The storey drift that were monitored as shown in below figure

5.5 Drift:

0

0.5

1

1.5

2

2.5

3

0 10 20 30

FLOATINGCOLUMN

0

100

200

300

400

500

600

0 10 20 30

FLOATING COLUMN

WITH COLUMN


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Fig.21 Storey drifts for floating column and normal building in X-direction.

Fig.22 Storey drifts for floating column and normal building in Z-direction.

5.6 Drift and Displacement

The most significant basic parameter monitored throughout the whole analysis process

was Drift and Displacement at the top story of the building. The following shows the

displacement & drift as follows

6. CONCLUSIONS:

The following conclusions are made from the present study.

6.1 Stiffness:

1) The use of floating column in R.C.C structure with regular geometry does not have any

effect on stiffness of building and it is efficient under lateral load if the structure is

carefully designed in view of beam column joints with ductile detailing as per IS

13920:1993.

6.2. Drift:

1) Both the cases show a gradual increase in drift from base to top story.

Case i) floating column building top story drift = 35 mm

Case ii) Normal building top story drift=39 mm

0

5

10

15

20

25

30

35

40

0 0.5 1 1.5 2

X IN CM F

X IN CM

0

10

20

30

40

0 0.5 1 1.5 2

Z IN CM F

Z IN CM


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2) In floating column building there is no major increase in the drift of the structure.

i)The drift was gradually increasing form base to top the drift is 9%

ii) By the providing floating column the drift increases to 10.8% at top story

iii) By the providing floating column the drift at floating column level is 9.1% increase

when comfit with the normal structure. This satisfies serviceability criteria.

3) In normal building there was a gradual increase of drift from base to top which was also

under the serviceability criteria.

4) When both the cases were compared the structure shows similar graph and found to be

10% more in floating column case

6.3. Axial forces:

1) The axial force for columns C1, C2 and C3, C4 and C5, C6 were equal as they are mere

image of each other.

In this the central columns are stressed more than the outer columns

Column C1:

Shear force and axial load:

There was a 6.7% increase in the floating column can while compared with normal

structure in Px.


structure in Py.


structure in Pz.

Bending moments:


structure in Mx.

There was a 162% increase in the floating column can while compared with normal

structure in My.


structure in Mz.

Column C2:



structure in Px.


structure in Py.


structure in Pz

Bending moments:


structure in Mx.


structure in My.


structure in Mz.

Column C3:


815



structure in Px.


structure in Py.


structure in Pz.

Bending moments:


structure in Mx.


structure in My.


structure in Mz

Column C4:



structure in Px.


structure in Py.


structure in Pz.

Bending moments:


structure in Mx.


structure in My.


structure in Mz.

Column C5:



structure in Px.


structure in Py.


structure in Pz.

Bending moments:


structure in Mx.


816


structure in My.


structure in Mz

Column C6:



structure in Px.


structure in Py.


structure in Pz

Bending moments:


structure in Mx.


structure in My.


structure in Mz.

Displacement:

1) Both the structures showed a gradual increase in displacement and graph shown similarly

Patten from base to top with an increase of 21.7%@ top when compared with normal case.

2) Displacement of the column C1&C2 in floating column building shows 21.7% increase in

compression to normal building.





As per the study and on compression of both the can it is found that the provision of floating

column is a structure in regular geometry does not have any effect on a structure and the design

in economical and serviceable under lateral loads for both cases.

7. SCOPE FOR THE FUTURE WORK

1. Further it should study for floating column at top floor and other position in building.

2. Complication caused by the provision floating column on the internal columns that are more

stressed (or) column which is more stressed should be studies. Behavior of column under Py

3. Floating column in irregular geometry

4. Research can also be done on steel floating column.

REFERENCES

[1] Srikanth.M.K, Yogendra.R.Holebagilu, “Seismic response of complex building with floating

column for zone II and zone V, International journal of Engineering Research, ISSN: 2321-7758

Vol.2., Issue.4, 2014, pp.1228-1234.


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[2] Priyankakumari,N.r.Dhamge. ”Analysis of multistoried building with floating column”,

International journal of scientific Research and development. Vol. 3, Issue.8, 2015 .ISSN: 2321-

0613

[3] T.Raja. Sekhar, P.V.Prasad,” Study of behavior of seismic analysis of multisttory building

with and without floating column”. Carib .j. SciTech, 2014, Vol2, Pp.697-710.

[4] PrernaNautiyal, Saleem Akhtar and GeetaBatham, “Seismic response evaluation of RC frame

building with floating column considering different soil conditions”, International Journal Of

Current Engineering And Technology, E-ISSN: 2277 – 4106,(February 2014), Pp.132-138.

[5] Shiwliroy, GargiDanda de, “Behavioural studies of floating column on framed

structure”International journal of research in engineering and technology, E-ISSN: 2319-1163,

Vol. 9, Issue 9, September 2015, pp.435-440.

[6] SreekanthGandlaNanabala, Pradeep Kumar Ramancharla, ArunakanthiE,”Seismic Analysis

of A Normal Building and Floating Column Building”, International journal of engineering

research and technology, ISSN: 2278-0181, Vol. 3, Issue 9, September 2014, pp.981-987.

[7] NiteenMalu, Amaresh.S.Patil, “Performance of RC frame structure with floating column and

soft storey in different earthquake zones using pushover analysis”, International research journal

of Engineering and technology, eISSN: 2395-0056, Vol.4., Issue.9, September 2017, pp.1228-

1234.

[8] Criteria for Earthquake Resistant design of structures, Part1: General provisions and

buildings, IS1893:2002, Bureau of Indian Standards, New Delhi.

[9] IS 875 (Part-I) Bureau of Indian Standards (1987) Code of Practice for Design Loads (Other

than Earthquake) for Buildings and Structures: Dead Loads-Unit Weights of Building Materials

and Stored Materials (Second Revision). UDC 624.042: 006.76.

[10] IS 875 (Part-II) Bureau of Indian Standards (1987) Code of Practice for Design Loads For

Buildings and Structures: Imposed Loads (Second Revision). UDC 624.042.3:006.76.

[11] Duggal S K (2010), “Earthquake Resistance Design of Structure”, Four Editions, Oxford

University Press, New Delhi.


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