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Need for structural reinforcement
• Change of use
• Deterioration
• Exceptional damage
• Changes in regulations
• Increase seismic resistance
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
Presentation Layout
Introduction to FRPs
Bonding FRP to timber
Applications of FRP
Design rules
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
Use of FRP in structural reinforcement
Fibre reinforced polymers (FRPs) widely used in the retrofit of concrete and masonry structures
Increasing use for metallic and timber structures due to decreasing costs, better understanding of behaviour
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
What are FRPs?
Composite material – two components
Fibre – load carrying component
Polymer matrix – transfers load between fibres, protection
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
Fibres & polymersFIBRESCarbonAramidGlassBasalt
POLYMERSMost widely used is epoxyCan be any polymer – vinylester, PA, etcMechanical properties much lower than fibres
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
COST MECHANICAL PROPERTIES
Type of FRPUnidirectional parallel fibresRods, plates, fabrics
Two‐dimensionalWoven fabricsLaminates
Three‐dimensional
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
Properties of FRP UD rods
FRP ρ (kg/m3) EL (GPa) UTS L (MPa) CTEL (/⁰C)
CFRP 1500‐1600 170‐300 2800‐1300 (‐1) – 0 e‐6
AFRP 1200‐1500 120 2900 (‐6 )– (‐2) e‐6
GFRP 1200‐2100 75 3400 6‐10 e‐6
BFRP 1900 >50 >1000 2e‐6
Steel 7900 200 400 11.7 e‐6
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
Advantages:Light weight, easy to handleCorrosion resistantHigh strength
Disadvantages:Expertise and skill requiredCost
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
Bonding FRP to timber
Adhesive bonding the principal method used to connect the FRP to the timber element
Resin applied to element, FRP applied to resin under pressure
Resin applied to fabric then applied to element – wet lay‐up
Cold‐cure epoxies most commonly usedCOST Action FP1101, WG2 Workshop, 21/06/13 Telč
Requirements for adhesives
Compatibility with and adhesion to timber substrateCompatibility with and adhesion to FRPFilling ability, workabilitySufficient opening timeAdequate mechanical propertiesResistance to environmental effects – temperature and moisture effects
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
Surface preparationTo maintain reliability of bond during service life
FRPAbrasion followed by solvent cleaning
orPeel ply method
TimberPlane within two hours of bonding
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
Applications of FRP strengthening Beams
Flexural reinforcementShear reinforcementEnd bearingsTension perp grain
FloorsIn‐plane strengthening
WallsIn‐plane strengthening
(Joints)COST Action FP1101, WG2 Workshop, 21/06/13 Telč
External plate bonding
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
Siaz Building, TreviCFRP & epoxy resin (2003)
Aare bridge, MurgentalCFRP & epoxy resin (2003)
[Steiger, 1999] [CNR, 2007]
External plate reinforcementSins Bridge
[Motavalli, 2012]
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
Pultruded FRP profiles
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
Palazzo Collicola, Spoleto (2004)GFRP profiles connected with
epoxy resin and GFRP shear connector
[Borri, 2005]
Shear strengtheningFRP plate or mesh on side faces or wrapped around sides and soffitShear spikes through beam depth
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
[Yang, 2013]
Near surface mounted rods/barsAdvantages: end anchorage, greater bond area; fire protection
[Juvandes, 2012] [Raftery, 2012]
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
Capacity of reinforced elementUltimate moment capacity ‐ solid mechanics
Enough tension reinforcement =>
compression yielding on top
Ductile response
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
Deformation
Load
Active v passive reinforcementPassive reinforcement
Stiffness increaseCFRP – goodOthers – limited
Active reinforcementPrestressing reinforcementPrecamber – effective stiffness increase
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
Tension perpendicular to grainCurved glulams, tapered beams, openings, connections
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
[Haiman, 2006]
Replacement of decayed beam ends
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
[Wheeler, 1998]
[Rotafix, 2013]
Unbonded pin‐loaded CFRP straps
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
St Marien Church
[Huster, 2008]
Design Guidelines – FRP ‐ timberItalian guidelines good starting point for EU‐wide documentCovers strengthening in
BendingBending and axial forceIn‐plane actionsJoints
COST Action FP1101, WG2 Workshop, 21/06/13 Telč
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