PUSH OVER ANALYSIS FOR RC BUILDING WITH AND ... PUSH OVER ANALYSIS FOR RC BUILDING WITH AND WITHOUT FLOATING COLUMNS Author Stella Evangeline, D.Satish, E V Raghava Rao Subject International

PUSH OVER ANALYSIS FOR RC BUILDING

WITH AND WITHOUT FLOATING COLUMNS

Stella evangeline 1, Student(m.tech) D.Satish 2, M.Tech (structures) E V Raghava Rao 3,

Civil engineering dept , Asst.professor, HOD of civil dept,

Visakha technical campus civil engineering dept, Visakha technical campus,

Visakhapatnam,,India Coastal institute of technology. [email protected].

[email protected]

Abstract— Rc structure and Floating column structure are typical

features in the modern multi-storey constructions in urban

India. Such features are highly undesirable in buildings

built in seismically active areas; this has been verified in

numerous experiences of strong shaking during the past

earthquakes like Bhuj 2001. In this study an attempt is made

to reveal the effects of floating column & rc building effected

with sesmic forces. For this purpose Push over analysis is

adopted because this analysis will yield performance level of

building for design capacity (displacement) carried out up to

failure, it helps determination of collapse load and ductility

capacity of the structure. To achieve this objective, three RC

bare frame structures with G+4 stories will be analysed and

compared the base force and displacement of RC bare frame

structure for earthquake forces by varing column

dimensions using SAP 2000 14 analysis package.

Keywords— floating column, rc structure, pushover analysis, earthquake

forces.

1. INTRODUCTION

Many urban multistorey buildings in India today have

open first storey as an unavoidable feature. This is

primarily being adopted to accommodate parking or

reception lobbies in the first storey. Whereas the

totalseismic base shear as experienced by a building

during an earthquake is dependent on its natural period,

the seismic force distribution is dependent on the

distribution of stiffness and mass along the height. The

behavior of a building during earthquakes depends

critically on its overall shape, size and geometry, in

addition to how the earthquake forces are carried to the

ground.

2.1 FLOATING CLOUMNS

Floating column is also a vertical member, The Columns Float

or move in above stories such that to provide more open space

is known as Floating columns. Floating columns are

implemented, specially above the base floor, so that added

open space is accessible for assembly hall or parking purpose.

For the study of the floating column many projects have been

undertaken where the transfer of load is through the girders.

Floating columns are usually adopted above the ground storey

level. So that maximum space is made available in the ground

floor which is essentially required in apartments, mall or other

commercial buildings where parking is a major problem.

But those structures cannot be demolished; rather study can be

done to strengthen the structure. The stiffness of these

columns can be increased by retrofitting or these may be

provided by bracing to decrease the lateral deformation.

Many high rise buildings are planned and constructed with

architectural complexities. The complexities are nothing but

soft storey, floating column, heavy load, the reduction in

stiffness, etc.

3. METHODLOGY

In the of case structures to avoid earth quake damages, special

arrangement needs to be made to increase the lateral strength

and stiffness of the members. As per IS 1893 (part-1): 2002,

Dynamic analysis (Linear or Non-linear) of building is carried

out including the strength and stiffness effects and inelastic

deformations in the members and the members designed

accordingly. The lateral loads due to earthquake were

calculated using Response spectrum method as per IS 1893

(part-1): 2002. CALCULATION OF BASE SHEAR

The total design lateral force or design seismic base shear (VB)

is calculated according to clause 7.5.3 of IS 1893:2002 (IS

1893:2002 is referred to as the Code subsequently).

The total Base shear

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Where A

h is the design horizontal seismic coefficient

Here

Z = Zone Factor

I = Importance Factor

R = Response Reduction Factor

The values of Z, I, R are given in Tables 2, 6, 7 respectively in

IS 1893 (part-1):2002.

Sa/g = Spectral acceleration coefficient. It is calculated

according to Clause 6.4.5 of the Code corresponding to the

fundamental time period Ta in seconds is given as follows.

For a Moment Resisting Frame without infill

For a Moment Resisting Frame with brick infill panels

Here

h = Height of the Building Frame

d = Base dimension of the building at the plinth level in

meters, along the considered direction of the lateral load s

PUSHOVER ANALYSIS

Pushover analysis is a static, nonlinear procedure in which the

magnitude of the lateral loads is incrementally increased,

maintaining a predefined distribution pattern along the height

of the building. Pushover analysis can determine the behaviour

of a building, including the ultimate load and the maximum

inelastic deflection. Local nonlinear effects are modelled and

the structure is pushed until a collapse mechanism is

developed. At each step, the base shear and the roof

displacement can be plotted to generate the pushover curve

NON-LINEAR STATIC ANALYSIS

The existing building can become seismically deficient since

seismic design code requirements are constantly upgraded and

advancement in engineering knowledge. Further, Indian

buildings built over past two decades are seismically deficient

because of lack of awareness regarding seismic behaviour of

structures. The widespread damage especially to RC buildings

during earthquakes exposed the construction practices being

adopted around the world, and generated a great demand for

seismic evaluation and retrofitting of existing building stocks.

In the figures below different nodes subjecting to different levels of elastic zone are represented with respective colors mentioned at the bottom of the figures. The elastic zone is categorized into three parts likely

Immediate Occupancy (IO)

Life safety (LS)

Collapse prevention (CP)

CASE 1 :

RCbuilding is considered with all beams and columns of same

dimensions and in the

CASE 2:

with the same structural dinmension for the same structure

floating cloumns are assumed and push over curves are

studies and in the

CASE 3:

by incresing the size of the surroubnding columns near the

Floating cloums the pushover curve is studied

CASE 4:

Floating columns are provided in the top floor and

surrounding columns dimensions are increased and push over

is studied and compared

The frames have to be designed so as to satisfy strength

checks under several load combinations. To start with, the

approximate values for dead loads have to be assumed based

on the usual range of geometric ratios such as span to depth

ratios for beams and widths of members. The earthquake loads

can also be assumed correspondingly to the plateau in the

response spectrum. In the current study, the length, width and

storey heights were 3.0 m .

Beam = 450x230 mm

Columns = 450x230 mm

= 600 x 400 mm

Pedestal Columns = 450x230 mm


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CASE 1 :- RC BUILDING WITH COLUMN,BEAMSOF

SIZE 450X230MM WITHOUT FLOATING COLUMNS

CASE 2 :-

RC BUILDING WITH COLUMN,BEAMSOF SIZE

450X230MM WITH FLOATING COLUMNS AT STILT

LEVEL

CASE 3 :-

RC BUILDING WITH COLUMN,BEAMSOF SIZE 450X230

MM WITH FLOATING COLUMNS AT STILT LEVEL

AND CHANGE IN DIMENSION OF STILT COLUMNS

600 X 400 MM .

CASE 4:

RC BUILDING WITH COLUMN,BEAMSOF SIZE 450X230

MM WITH FLOATING COLUMNS AT TOP FLOOR AND

CHANGE IN DIMENSION OF SURROUNDING

COLUMNS TO 600 X 400 MM


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PUSH OVER CURVES

CASE 1:

CASE 2:

CASE 3:

CASE 4:

HINGE FORMATION

CASE 1:

CASE 2:

CASE 3:

CASE 4:


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EVALUATION RESULTS

RESULT 1:

STEP DISPLACEMENT

KN BASE

FORCE

DISPLAC

MENT

CHANGE

IN %

BASE FORCE

CHANGE %

48 0.222433

2036.84

7 0.127312

1604.986

21.20

49.40

RESULT 2:

STEP DISPLACEM

ENT KN

BASE

FORCE

DISPLACME

NT CHANGE

IN %

BASE

FORCE

CHANG

E %

48

(COLU

MN

SIZE

.45 X

.23)

0.22243

2036.842

7(COL

UMN

SIZE .6

X .4 )

0.079255

2498.647

18.4

64.3

RESULT 3:

STEP DISPLACEM

ENT KN

BASE

FORCE

DISPLACM

ENT

CHANGE

IN %

BASE

FORCE

CHANGE

%

48

(COLU

MN

SIZE

.45 X

.23)

0.222433

2036.842

7(COL

UMN

SIZE .6

X .4 )

0.127312

2036.366

42.7369

0.0233

RESULTS AND DISSCUSSIONS

1. With the increase in the stilt column dimensions the

displacement varies and base force also increases.

2 .Increase in 150 mm dimension in slilt-cloumns results 62

% variation in the base force.

3.With increase in the surrounding columns near floating

columns. The base shear will be increased.

4. By providing floating columns at the top floor and with

increase in the surrounding columns the displacement and

base force decreases.

5.For existing rc buildings effected by earthquakes, and

tsunami the column size and be increased by method of

shorcreting.

REFERENCES

[1]. Srikanth.M.K, Yogeendri.R.Holebagilu, “Seismic

Response Of Complex Buildings With Floating Column For

Zone II and Zone V”, International journal of Engineering

Research-Online, Vol.2., Issue.4, 2014, ISSN: 2321-7758.

[2]. Spoorthi S K, Dr. Jagadish Kori G, “Effect Of Soft Story

On Tall Buildings At Various Stories By Pushover Analysis”,

International journal of Engineering Research-Online, Vol.2.,

Issue.3., 2014, ISSN: 2321-7758.

[3].RizaAinul Hakim, Mohammed SohaibAlama, Samir A.

Ashour, “Seismic Assessment of an RC Building Using Pushover Analysis”, Engineering, Technology & Applied Science Research Vol. 4, No. 3, 2014, 631-635.

[4]. Naga Sujani.S, Phanisha.K, MohanaRupa, Sunita Sarkar, P.Poluraju, “Comparison of behavior of a multistorey building situated in zone II and zone V, using pushover analysis by Sap 2000”, International Journal of Emerging Trends In Engineering And Development, Issue 2, Vol.2(March-2012), Pp. 480-487.

[5]. SukumarBehera, “Seismic Analysis Of Multistory Building With Floating Column” A Thesis Of National Institute Of Technology Rourkela, (2012), Pp. 21-93.

[6]. Amit V. Khandve. (2012), “Seismic Response of RC Frame Buildings with Soft Storeys”, International Journal of Engineering Research and Applications (IJERA), vol 2, Issue 3, pp 2100-2108.

[7]. Mehmet Inel, Hayri. B. Ozmen. (2008), “Effect of infill walls on soft story behavior in mid-rise RC Buildings”, The 14th World Conference on Earthquake Engineering, Beijing, China, pp 12-17.

[8]. Federal emergency management agency (FEMA 356), Nov 2000, is a report on Prestandard and commentary for the seismic rehabilitation of buildings prepared by American society of civil engineers.

[9]. Ri-Hui Zhang1 and T. T. Soong, Member, ASCE “Seismic Design of Viscoelastic Dampers for Structural Applications” J. Struct. Eng. 1992.118:1375-1


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PUSH OVER ANALYSIS FOR RC BUILDING WITH AND ... PUSH OVER ANALYSIS FOR RC BUILDING WITH AND WITHOUT FLOATING COLUMNS Author Stella Evangeline, D.Satish, E V Raghava Rao Subject International