coposite profiled beam
TRANSCRIPT
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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 stress- strain 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
Bending Stress-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
Bending Stress-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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