Annette Harte (NUI Galway) Kay Uwe Schober (is Mainz) COST Action FP1101, WG2 Workshop Telč
Need for structural reinforcement Change of use Deterioration Exceptional damage Changes in regulations Increase seismic resistance
Presentation Layout Introduction to FRPs Bonding FRP to timber Applications of FRP Design rules
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
What are FRPs? Composite material two components Fibre load carrying component Polymer matrix transfers load between fibres, protection
Fibres & polymers FIBRES Carbon Aramid Glass Basalt COST MECHANICAL PROPERTIES POLYMERS Most widely used is epoxy Can be any polymer vinylester, PA, etc Mechanical properties much lower than fibres
Type of FRP Unidirectional parallel fibres Rods, plates, fabrics Two dimensional Woven fabrics Laminates Three dimensional
Properties of FRP UD rods FRP ρ (kg/m 3 ) E L (GPa) UTS L (MPa) CTE L (/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
Advantages: Light weight, easy to handle Corrosion resistant High strength Disadvantages: Expertise and skill required Cost
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 used
Requirements for adhesives Compatibility with and adhesion to timber substrate Compatibility with and adhesion to FRP Filling ability, workability Sufficient opening time Adequate mechanical properties Resistance to environmental effects temperature and moisture effects
Surface preparation To maintain reliability of bond during service life FRP Abrasion followed by solvent cleaning or Peel ply method Timber Plane within two hours of bonding
Applications of FRP strengthening Beams Flexural reinforcement Shear reinforcement End bearings Tension perp grain Floors In plane strengthening Walls In plane strengthening (Joints)
Flexural reinforcement [CNR, 2007]
External plate bonding Aare bridge, Murgental CFRP & epoxy resin (2003) Siaz Building, Trevi CFRP & epoxy resin (2003) [Steiger, 1999] [CNR, 2007]
External plate reinforcement Sins Bridge [Motavalli, 2012]
Pultruded FRP profiles Palazzo Collicola, Spoleto (2004) GFRP profiles connected with epoxy resin and GFRP shear connector [Borri, 2005]
Shear strengthening FRP plate or mesh on side faces or wrapped around sides and soffit Shear spikes through beam depth [Yang, 2013]
Near surface mounted rods/bars Advantages: end anchorage, greater bond area; fire protection [Juvandes, 2012] [Raftery, 2012]
Capacity of reinforced element Ultimate moment capacity solid mechanics Load Enough tension reinforcement => compression yielding on top Ductile response Deformation
Active v passive reinforcement Passive reinforcement Stiffness increase CFRP good Others limited Active reinforcement Prestressing reinforcement Precamber effective stiffness increase
Tension perpendicular to grain Curved glulams, tapered beams, openings, connections [Haiman, 2006]
Replacement of decayed beam ends [Wheeler, 1998] [Rotafix, 2013]
Floors in plane reinforcement [Corradi, 2006]
Timber frame walls [Al Muman, 2012]
Reinforcement of walls [Al Mumad, 2012]
Walls In plane reinforcement [Premrov, 2004]
Unbonded pin loaded CFRP straps St Marien Church [Huster, 2008]
Non laminated CFRP straps [Huster, 2008]
Design guidelines RC & Metallic structures
Design Guidelines FRP timber Italian guidelines good starting point for EUwide document Covers strengthening in Bending Bending and axial force In plane actions Joints
Thank you!