coposite profiled beam

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Experimental Investigation ofComposite Profiled Beams


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OBJECTIVE

To determine the strength parameters for the rectangular and

trapezoidal composite profiled beam.

To compare the result of conventional and composite profiled

beams both experimentally and theoretically.


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Composite Structures

Introduction

Composite structure refers to two load carryingstructural members that are integrally connected and deflect asa single unit. .

In Reinforced concrete beams that use steel deckingconsisting of profiled as permanent form to both the soffit andsides of the beam. This form of beams are called profiled beams.

It is now common practice to use cold formed steel decksconsisting of profiled sheets both as permanent formwork forthe support of soffits of reinforced concrete slab and also as partof the tension steel in the composite profiled slab that is formedafter the concrete has hardened.


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ADVANTAGES OF COMPOSITE

PROFILED BEAM

Reduction in site manpower, Faster construction.

Materials are easily available.

Formwork is not required.

Depth of section may be reduced, reduction inweight and reduction in story height.

Provided only few numbers of props.

Reduced noise levels, absence of centering.

Safer working environment. Profiled sheets act as a tension member, so it is

satisfactory to provide a nominal reinforcement.


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PRELIMINARY TESTS OF CONCRETE

CONCRETE MIX DESIGN

The mix design was arrived M20 grade of concrete as per

IS: 10262-2009. The proportion found from mix design was

1:2.04:3.36:0.55(Cement: Fine Aggregate: Coarse Aggregate:Water) with a cement content of 348.320 kg/m3.


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MIX PROPORTION FOR ONE METER CUBE

OF CONCRETE

Sl no Materials Weight in kg/m3

1 Cement 348.320

2 Fine Aggregate 711.274

3 Coarse Aggregate 1172.000

4 Water 191.5805 Water Cement Ratio 0.55


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CONCRETE TEST RESULTS

The compressive strength of concrete is 28.58 N/mm2

The compressive strength of concrete is greater than the

targeted mean strength of concrete.

The split tensile strength of concrete is 2.64 N/mm2.Thetensile strength of concrete is about 1/10 of the compressive

strength of concrete.

The modulus of rupture is 3.923 N/mm2 .This value

closely agrees with modulus of rupture calculated based on IS456:2000


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Cross section details


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Cont.


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Conti.


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FABRICATION OF PROFILED SHEET

Pressing Machine


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COLD FORMED PROFILED SHEET


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THEORETICALCALCULATIONS

STRESS BLOCK PARAMETERS


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Conti.

All the cross section is planned to have equal concretearea.

Considering the bottom of profiled sheet act as a tensilereinforcement but not consider sides of profiled sheet.

From the stress block diagram, the depth of Neutral Axisand Moment carrying capacity are calculated by the followingequations,


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THEORETICAL MOMENT CARRYING CAPACITY OF

BEAMS

Beam

designation

Depth of NA Moment carrying

capacity

Load carrying

capacity

CB1 34.420 9.987 21.775

CB2 21.950 6.688 14.361

PRB1 63.360 14.540 32.040

PRB2 48.760 12.11026.579

PTB1 41.890 16.225 35.826

PTB2 31.356 12.970 28.514


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Conti.

From the theoretical computations, it is observed that

the moment carrying capacity of the composite profiled beam

is estimated as 45% - 62% higher than the moment to be

carried by conventional concrete beam.

Among the composite profiled beams, the trapezoidal

profiled beam seems to have 10% - 20% higher load carrying

capacity compared to rectangular profiled beam.


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Experimental setup for Composite

Specimen


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ULTIMATE LOAD AND ITS CORRESPONDING

DEFLECTION(Experimental)

Beam

designation

Ultimate

load(kN)

MID SPAN

DEFLECTION

L/3

DELECTION

CB1 35.190 9.403 7.512

CB2 30.213 8.309 6.603

PRB1 78.036 15.127 11.771

PRB2 67.300 13.511 10.667

PTB1 87.568 16.41 12.805

PTB2 78.030 14.623 11.406


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Load - Mid Span Deflection curves of

all Specimens

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18

LoadinkN

Deflection in mm

Load vs Mid Span Deflection

CB1 CB2 PRB1 PRB2 PTB1 PTB2


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EFFECTS OF PROFILED CONFIGURATION

Profiled

rectangular

Beam

designation

Ultimate

load (kN)

Profiled

trapezoidal

beam

designation

Ultimate

load (kN)

% increase

of ultimate

load

(kN)

PRB1 78.036 PTB1 87.568 12.22

PRB2 67.300 PTB2 78.030 15.94


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Conti

Table shows the Percentage increase of ultimate load of

Composite Profiled Beam with different profiled

configuration. It is found PTB is 12 16 % more than PRB.


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STIFFNESS

Stiffness may be defined as load required causing a unit

deflection. The stiffness values of conventional specimens and

composite profiled specimens at elastic load. The slope values

of load deflection curve are the stiffness value within elastic

limit.


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STIFFNESS VALUES AT ELASTIC LOAD

Beam Designation Stiffness(kN/mm)

CB1 4.451

CB2 4.350

PRB1 7.997

PRB2 6.401

PTB1 9.220

PTB2 8.508


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Conti

Table shows the elastic stiffness values of composite

profiled beams and conventional specimens. It is observed

that the composite profiled beams have high stiffness values

than conventional specimens at elastic load. The profiled

trapezoidal beams have 15-32 percentages more stiffness

than the rectangular profiled beams.


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ENERGY ABSORPTION

Energy absorption is the energy absorbed or stored by a

member when work is done on it to deform it and is called

strain energy or resilience.

Energy absorption is calculated as the area under the

load versus mid span deflection curve up to elastic load

beyond the elastic load. The energy absorption values of

control beams and composite profiled beams are shown in

table


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Conti

It shows that Composite profiled beams have moreenergy absorption capacity than that of RC beams up toelastic loading and beyond the elastic loading.

This shows that profiled beams with 10 mm diameterrod offered more resistance to the applied load. Whilecomparing the profiled beams, beam with trapezoidal crosssection shows more energy absorption capacity than thatof beams with rectangular cross section.

However it is concluded that there is a significantincrease in energy absorption due to cross sectionalconfiguration or depth of the section and thickness ofreinforced steel bar.


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ENERGY DUCTILITY

The energy ductility may be defined as the ratio of the

energy absorbed up to ultimate load to energy absorbed up to

elastic load. It may be obtained by dividing the area under the

load-deflection curve up to ultimate load, by the area under

load-deflection curve up to elastic load


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ENERGY DUCTILITY

Beam

designation

Energy

Absorption

upto Elastic

Load in kN-mm(A)

Energy

Absorption

upto Ultimate

Load in kN-mm(B)

Energy

ductility

I=B/A

CB1 119.974 197.527 1.646

CB2 80.787 145.796 1.800

PRB1 284.486 742.649 2.610PRB2 237.326 556.725 2.346

PTB1 389.143 907.156 2.331

PRB2 350.538 714.074 2.037


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LOCAL BUCKLING

Plate element of cross section may buckle locally due to

compressive stress

The following figures display the development of local

buckling of the composite profiled beams. From the figure wecan clearly understand that there is no De-bonding

developed in the composite profiled beams.


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Buckling and Crushing failure of Profiled

Rectangular Beam


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Buckling and Crushing failure of profiled

Trapezoidal Beams


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Buckling and Crushing failure of all Profiled

Beams


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BENDING STRESSSTRAIN CURVE

Bending strain measured at top and bottom surface of the specimen by

using electrical strain gauges. The resistance of strain gauge is 350 ohms.

The 3mm size of strain gauge is placed at bottom of profiled sheet in mid

span. The 10mm size strain gauge is placed at top surface of all specimens

in mid span. The compression strain is taken as negative and tensile strain is

taken as positive.

-5

0

5

10

15

20

-0.002 -0.001 0 0.001

BendingStressN/mm2

strain

Bending Stress-strain

plot(CB1)

At Top

0

2

4

6

8

10

12

14

16

-0.002 -0.001 0 0.001

Bendin

gstressN/mm2

strain

Bending Stress-strain plot (CB2)

At Top


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0

5

10

15

20

25

30

35

40

-0.003 -0.002 -0.001 1E-17 0.001 0.002 0.003

Bend

ingstressN/mm2

strain

Bending stress -strain

plot(PRB1)

At Bottom At Top

0

5

10

1520

25

30

35

-0.002 -0.001 1E-17 0.001 0.002 0.003

Bendingst

ressN/mm2

strain

Bending stressstrain plot(PRB2)

At Bottom At Top

-5

0

5

10

15

20

25

30

35

40

-0.004 -0.002 0 0.002 0.004

Ben

dingstressN/mm2

strain


plot(PTB1)

At Bottom At top

-10

0

10

20

30

40

-0.002 -0.001 3E-18 0.001 0.002 0.003

BendingstressN/mm2

strain


plot(PTB2)

At Bottom At top


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MOMENT-CURVATURE

Moment-curvature diagram of a section in bending can

be theoretically computed from the assumptions of the

bending theory by calculating the corresponding values of M

and . The theoretical stress-strain curves for steel and

concrete, together with the equation of equilibrium andcompatibility, are used for this purpose.


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MOMENT-CURVATURE OF TRAPEZOIDAL

PROFILED BEAMS

y = -4E+10x2 + 2E+06x + 1.129(PTB1)

y = -5E+10x2 + 3E+06x + 2.414(PTB2)

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

0 0.000005 0.00001 0.000015 0.00002 0.000025

MomentinKN-m

Rotation in radians

Moment curvature plot(PTB)

PTB1

PTB2

Poly. (PTB1)

Poly. (PTB2)


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Conti.

The equation of moment curvature for profiled

rectangular beams is

M = -3*1010 2 + 2*106 + 1.927 (PTB1)

M = -5*1010

2

+ 2*106

+ 1.389 (PRB2)The equation of moment curvature for profiled

trapezoidal rectangular beams is

M = -4*1010 2 + 2*106 + 1.129 (PTB1)

M = -5*1010 2 + 3*106 +2.414 (PTB2)


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COMPARISION BETWEEN THERORETICAL

VALUE AND EXPERIMENTAL RESULTS

Beam

designation

Ultimate

load(kN) from

experimental

results

Ultimate

load(kN) from

theoretical

valueCB1 35.190 21.775

CB2 30.213 14.361

PRB1 78.036 32.040PRB2 67.300 26.579

PTB1 87.568 35.826

PTB2 78.030 28.514


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CONCLUSION

The following are the conclusion drawn from the experimentalwork for flexural specimens.

The ultimate strength ,load deflection curve and crack patternwere studied for conventional beams. Since the beams wereunder reinforced, yielding of the tensile reinforcement

occurred in pure bending. The ultimate load of composite profiled is ranges from 2.23-

2.6 times of conventional beams. While comparing theprofiled beams, the ultimate load of PTBs carried 12.3-16percentage more than PRBs.

For normal trapezoidal beam the form work is costly anddifficult to place. Since the trapezoidal profiled sheets areprefabricated so it can be used easily in construction industry.

i


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Conti

Stiffness, Energy absorption capacity, Energy ductility are dependson the profiled cross section and diameter of steel bar.

Composite profiled beams shows large amount of energy absorptioncapacity that of RCC beams and also PTBs more energy absorptioncapacity.

Provision of lips gives good bonding between concrete and profiledsheet.

Local buckling and crushing failure occurred ,when the composite

profiled beams almost reaches maximum load.

The addition of profiled sheet to the sides of reinforced concretebeams increase flexural strength. While increasing area of reinforcementin profiled beam more stiffness and reduces ductility.


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REFERENCE

Deric John Oehlers (1993)- Composite Profiled Beams

journal of structural engineering, Vole 119, No.4 April 1993.

ASCE page 3320.

Deric John Oehlers, Howard D,Wrightand Matthew j. Burnet

Flexural strength of profiled beams journal of structuralengineering, Vol 120, No 2. February, 1994. ASCE, Page NO.

4960

Brian Uyand Mark Andrew Bradford, Member ASCE - Ductility

of profiled composite beams. Part 1: Experimental study 1995Vol 121, No.5 May 1995. ASCE page 7851.

Brian Uy and Mark Andrew Bradford, Member ASCE -

Ductility of profiled composite beams. Part 2: Analytical

study 1995. Vol 121, No.5 May 1995. ASCE page 7852.


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Conti

Kottiswaran N and Sundararajan R (2005) An Experimentalinvestigation on flexural behaviour of steel concrete compositebeam made up of thin walled cold formed steel.

Hyung-JoonAhn and Soo-Hyun Ryu (2006) Modular composite profilebeams.

ArivalaganSundararajan, KandasamyShanmugasundaram *2008+ AnExperimental study of normal mix, flyash, quarry waste, and lowstrength concrete (Brick-bat lime concrete) contribution to theultimate moment capacity of square steel hollow sections.

Siva A and Kumar V(2012) Shear bond characteristics of compositeslab made of cold-formed profiled steel sheeting.

S.Ramamrutham (2006) Design of Reinforced Concrete Structures. IS 1022:2009 concrete mix proportioning guidelines.

IS 456: 2000 plane and reinforced concrete code of practice


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coposite profiled beam

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