COMPARATIVE PERFORMANCE OF FRP & FRCM SYSTEMS AT …
Transcript of COMPARATIVE PERFORMANCE OF FRP & FRCM SYSTEMS AT …
COMPARATIVEPERFORMANCE OF FRP &FRCM SYSTEMS ATELEVATED TEMPERATUREDr Luke Bisby, Reader
BRE Centre for Fire Safety EngineeringSchool of Engineering, University of Edinburgh, UK
Introduction• Externally-Bonded FRP Strengthening Systems
– Widely accepted, method of choice, polymer-based (concerns infire)
• Textile Reinforced Mortar (TRM) Strengthening Systems:– Emerged in last 5-10 years– Repairing damaged or deficient concrete or masonry (axial, shear,
flexure)– Open-weave carbon fibre fabrics applied using inorganic mortars– Comparatively low strength, stiffness, adhesion properties
• Fibre Reinforced Cementitious Matrix (FRCM) Systems:– Emerged in last 5 years– Non-woven PBO fibre grids applied using
modified inorganic mortars– Repairing damaged or deficient concrete– Superior strength, stiffness, adhesion
Ruredil X Mesh GoldTM
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Research Motivation• Thermal & mechanical performance
in fire– A key issue in the application of any
structural strengthening system
• Fire-rated, insulated externallybonded FRP strengthening systemsare available– Current design guidance ignores the
FRP during fire (even with insulation)– Ability of FRP strengthening systems to
maintain structural effectiveness underload at high temperature remainsunproven
– Applications of FRPs are hindered
• It has been suggested thatTRM/FRCM systems mayoutperform FRP systems during fireor in elevated temperature serviceenvironments
www.ruredil.it
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Background• FRCM:
– Advantages over externally bondedFRP systems:
• Installation and aesthetics• Breathability• Non-combustibility, zero flame spread• Mechanical performance at high
temperature?
• Current presentation:– Pilot study into comparative performance of FRCM
systems– Tests at ambient & elevated temperatures– Comparison against externally-bonded
carbon/epoxy FRP strengthening systems
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QUESTION: How does FRCM compare withFRP?
OBJECTIVES:
1. Experimentally investigate the performance of FRCMflexural strengthening systems for reinforced concretestructures
– In comparison with externally-bonded FRP systems– In bond-critical applications without supplemental anchors– At temperatures that they might experience if insulated and
exposed to a standard fire scenario, or in elevatedtemperature service environments
2. Investigate the hypothesis that FRCM systems mayprovide superior retention of mechanical propertiesat elevated temperature as compared with externally-bonded FRP
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Experimental Programme
• 36 notched beam bond tests
• Three strengthening systems:– FRCM system– FRP 1 system from an Italian supplier– FRP 2 system from a global FRP supplier
• Three test temperatures (tested @ hightemperature):– 20°C– 50°C– 80°C
• All tests performed in triplicate
6 hours pre-conditioning prior to testing
0
10
20
30
40
50
60
70
80
90
0 60 120 180 240 300 360 420Time (minutes)
Tem
pera
ture
(deg
. C)
80 deg. C
50 deg. C
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Beam Specimens
Strengthening system
Notch
400
600
36
A
A
80
150
18
150
100
1 layer FRP 2 layers FRCM
Bond breaker18
100
U-wraps for shearstrengthening
U-wraps for shearstrengthening
200 50
SIDE ELEVATION
FRP STRENGTHENED SECTION A-A FRCM STRENGTHENED SECTION A-A
* All dimensions in mm
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Shear Strengthening Scheme• Pilot tests demonstrated shear failures• Remedial shear strengthening was required
– Inverted U-wraps– shear strengthening without supplemental anchorage– Does not significantly affect the flexural strengthening
Strengthening system
400 100100
Major shear crack
FRP strengthening systemNo. 1
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Testing Matrix
3X Mesh M750X MeshGold
--FRCM 80
3Saturant Nº22Carbonfibre3
Primer Nº22FRP Nº2 80
3Saturant Nº11Carbonfibre3
Primer Nº11FRP Nº1 80
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680------PC 80
3X Mesh M750X MeshGold
--FRCM 50
3Saturant Nº22Carbonfibre3
Primer Nº22FRP Nº2 50
3Saturant Nº11Carbonfibre3
Primer Nº11FRP Nº1 50
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650------PC 50
3X Mesh M750X MeshGold
--FRCM 20
3Saturant Nº22Carbonfibre3
Primer Nº22FRP Nº2 20
3Saturant Nº11Carbonfibre3
Primer Nº11FRP Nº1 20
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--20------PC 20
No. ofbeams
Durationof
heating(hrs)
Targettest
temp.(°C)
Adhesivesystem
FibresystemPrimerSpecimen
ID
1 Commercially available epoxy primer and saturant system currently selling in Italy.2 Commercially available epoxy primer and saturant system currently selling globally.3 Commercially available unidirectional carbon fibre fabric currently selling in Italy.
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FRCM Installation
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Testing Methodology
Applied load
Linearpotentiometer
200 10050
Pin
ConcretebeamThermocouple
Reaction beam
50200
Strengthening systemgeoPIV region
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0
5
10
15
20
25
30
0 1 2 3 4 5Crosshead displacement (mm)
Load
(kN
)
FRP No2 20RC 20FRCM 20FRP No1 20
Load vs. Displacement: Tests @20°C
Shear Failure
Flexural Failure
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Failure Modes: 20°CUnstrengthened
FRP 1 strengthened
FRP 2 strengthened
Flexural failure
Shear failure
Shear Failure
Painted texture for digital image analysis
FRCM strengthened
Shear Failure
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Load vs. Displacement: Tests @50°C
0
5
10
15
20
25
30
0 1 2 3 4 5
Crosshead Displacement (mm)
Load
(kN
)
FRCM 50FRP No1 50FRP No2 50RC 50
Shear Failure
Flexural Failure
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Failure Modes: 50°CUnstrengthened
FRP 1 strengthened
FRP 2 strengthened
Flexural failure
Flexural / bond failure
Shear Failure
FRCM strengthened
Shear Failure
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Load vs. Displacement: Tests @80°C
0
5
10
15
20
25
30
0 1 2 3 4 5
Crosshead Displacement (mm)
Load
(kN
)
FRCM 80FRP No2 80RC 80FRP No1 80
Shear Failure
Flexural Failure
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Failure Modes: 80°CUnstrengthened
FRP 1 strengthened
FRP 2 strengthened
Flexural failure
Flexural / bond failure
Flexural / bond Failure
FRCM strengthened
Shear Failure
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Effect of Temperature
0.0
0.2
0.4
0.6
0.8
1.0
1.2
10 20 30 40 50 60 70 80 90
Temperature (deg. Celsius)
Nor
mal
ized
Fai
lure
Loa
d
FRCMFRP No1FRP No 2
Shear failure in concrete
Debonding failure of strengthening
Strength reduction of FRCM beams may be due to reductionsin shear strength of concrete at 80°C, rather than indicating
damage to the FRCM
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Aside: Characterization of EpoxyResins
• DMTA testing on polymer primer & saturants
0.000E+00
5.000E+08
1.000E+09
1.500E+09
20.0 50.0 80.0
Temperature (deg. C)
Mod
ulus
(Pa)
FRP No 1 Primer
FRP No 1 SaturantFRP No 2 PrimerFRP No 2 Saturant
Stiffness required toprevent bond failure
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Conclusions1. The FRCM system can be effectively used, without
supplemental anchorage, to strengthen RC beams inbending
2. Effects of Temperature:– FRP Nº1 experienced reductions of 52% at 50°C and 74% at
80°C– FRP Nº2 experienced reductions of 10% at 50°C and 64% at
80°C– FRCM experienced reductions of only 6% at 50°C and 28% at
80°C• May represent a reduction in the strength of the concrete rather
than damage to the FRCM system
3. FRCM appears to be a superior candidate for use instrengthening applications at temperatures of 25°C to80°C
4. FRCM’s inherent non-combustibility and superiorperformance at temperatures up to 80°C make it anattractive system for structural strengthening(particularly in buildings)
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Acknowledgements
The OveArupFoundation
Thank you for your attentionFor additional information email: [email protected]
Dr T Stratford, J Smith, SHalpinUniversity of Edinburgh
Ruredil SPA,Milano, Italy
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Aside: Flame Spread &Combustibility
• FRP systems:– Loss of the strengthening systems’ mechanical performance during
fire may not be critical if reasonable strengthening limits are imposed
• Structural performance is only one of many concerns infire:– Fire severity and fuel load– Flame spread– Smoke generation and toxicity
• FRP strengthening systems often require flame spreadcoatings in interior applications to meet life-safetyobjectives in fire
• FRCM systems bonded with inorganic mortars:– Inherently non-combustible– Can be used unprotected– Reductions in material and installation costs– Improved aesthetics
Aside: Aging of Polymer Resins?
• DMTA testing after 3 hrs at high temperature
0.000E+00
5.000E+08
1.000E+09
1.500E+09
2.000E+09
20 50 80Temperature ( oC)
Mod
ulus
(Pa)
FRP1 PrimerFRP1 Saturant
FRP No1 FRP No2