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Fire Resistance of Concrete Beams Reinforced with FRP Bars.

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Title: Fire Resistance of Concrete Beams Reinforced with FRP Bars.


1
Fire Resistance of Concrete Beams Reinforced with
FRP Bars.
  • Fire Safety Engineering Research and Technology
    Centre (FireSERT)
  • University of Ulster
  • Nadjai, A

BEng(H),MSc, PhD, CEng, MIStructE, MCIB
2
INTRODUCTION
In recent years, there has been significant
interest in the use of fibre-reinforced polymers
(FRP) in civil engineering applications due to
the advantages, such as
  • High Strength
  • durability
  • lower cost
  • EXTERNAL REINFORCEMENT (FRP)
  • Wrapped around the columns
  • bonded to the tension face of beams or slabs

INTERNAL REINFORCEMENT (FRP) As continuous
internal reinforcement in concrete structures
3
CHARACTERISTIC MATERIAL OF FRP
The FRP bars characteristic material behaviour
is linear up to failure. This property makes its
structural behaviour brittle, and the concrete
becomes the ductile component (by crushing of
concrete) of reinforced concrete structures
Besides, the low elastic modulus of the FRPs
results in high deformability, lack of ductility,
and high crack widths.
4
TIMELINESS AND NOVELTY
  • There is a clear need for improved understanding
    of the performance of materials in fire
  • to ensure adequate levels of safety
  • to provide clear design guidance,
  • produce cost-effective design solutions.

An improvement in the structural performances of
concrete beams can be obtained using
  • a combination of FRP and steel reinforcements
    seems to be
  • a practical and effective design solution for
    concrete beams
  • subjected to fire situations.

5
EFFECT OF FIRE ON THE CONCRETE STRENGTH
  • Initially, the heat applied to the concrete beams
    causes evaporation of free moisture in the
    concrete.
  • With a continued exposure to fire, the
    temperature in side the beam increases and the
    strength of concrete decreases.
  • In certain cases, the pressure generated by
    conversion of moisture into beams may be too high
    for the surface layer of concrete to resist, and
    it may spall causing a reduction in concrete
    compressive strength.

6
EFFECT OF FIRE EXPOSURE ON FRPs MECHANICAL
PROPERTIES
Temperature reduction factor for FRP tensile
strength
7
GFRP rebars
KE 1 for 0T100 KE
(1.25-0.0025T) for 100T300 KE (2.0
0.005T) for 300T400 KE 0
for 400T
AFRP rebars
KE 1 for 0T100 KE
(1.25-0.0025T) for 100T300 KE (2.0
0.005T) for 300T400 KE 0
for 400T
CFRP rebars
KE 1 for
0T100 KE (1.175-0.00175T) for
100T300 KE (1.625 0.00325T) for
300T500 KE 0
for 500T
Temperature reduction factor for FRP
modulus of elasticity
8
Flexural Capacity of Reinforced Beam Using the
Slices Approach
The programme is based on the method of the slice
approach
Taking into consideration the material properties
of steel and concrete function of their
temperature variation
9
Material properties at Elevated Temperatures
Material response within the structure is
controlled by the temperatures at point within
the section using Eurocode 2 part 1.2.
400N/mm2
20oC
?S
40N/mm2
?C
400oC
20oC
400oC
600oC
500oC
800oC
700oC
?C
?S
Concrete stress-strain curves
Steel stress-strain curves
10
TEMPERATURE PROFILE IN REINFORCED RECTANGULAR
BEAMS
The temperature contours are assumed to be
parallel to the vertical faces and the soffit of
the beam exposed to fire on these three
faces. Which based on interpolation of
temperatures measured by thermocouples at various
locations.
Temperature contours
T (D Ax Bx2 Cx3)/r0.25
A 3.33(30.0033t (100 t)/b
B 0.085 C 0.000221 D 475r7/12 (b
105t1/3)
This method is limited to rectangular beams
100ltblt300
1 r h/b3
1r3
11
DEFLECTION PREDICTION
for Mlt Mcr
for Magt Mcr
Load and curvature distribution along simply
supported beam
12
(No Transcript)
13
Ulsters tests
14
(No Transcript)
15
Approach method compared with Maria Antoniettas
experimental results
16
PARAMETRIC STUDY
200
25
25
225
50
25
150
FRP
SPAN 3 m
STEEL
Concrete compressive strength 35 Mpa
17
Load (KN)
Deflection (mm)
Loads deflections curves for beam reinforced
with steel and AFRP
18
Load (KN)
Deflection (mm)
Loads deflections curves for beam
reinforced with steel and CFRP
19
Load (KN)
Deflection (mm)
Loads deflections curves for beam reinforced with
steel and GFRP
20
CONCLUSIONS
  • Further development is under consideration like
    shear
  • and deflection in beams
  • Further experimental tests needs to done at
    elevated
  • temperatures for

1- beams with CFRP strengthening/repair 2-beams
reinforced with CFRP REBARS
  • In general the approach method is satisfactory

21
FireSERT - Europes most up to date Fire
Research Facility
  • Single Burning
  • Item (SBI)

Multi purpose combination furnace BS EN 1363 -
1366 with 50T 125T loading
10 Mw Calorimeter
23/10/2009 - Presentation Title
22
THANK YOU FOR YOUR ATTENTION !
International Symposium on Bond Behaviour of FRP
in Structures 8-10 December 2005 Hong Kong
Organised The International Institute for FRP in
Construction (IIFC)
http//www.iifc-hg.org
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