Post on 07-Jun-2018
CONCRETE: 21st Century Superhero - Building a sustainable future London, 22-24 June 2009
FRP REINFORCEMENT FOR DURABLE CONCRETE
STRUCTURES
Maurizio Guadagnini, Kypros PilakoutasKyriacos Neocleous, Iman Hajirasouliha
University of Sheffield
Stijn MatthysMagnel Laboratory for Concrete Research, Ghent University
CONCRETE: 21st Century Superhero - Building a sustainable future London, 22-24 June 2009
What are FRPs?
FibresProvide strength and stiffness
carbon, glass, aramid, basalt
MatrixProtects and transfers
load between fibres
epoxy, vinyl ester
CompositeFibres and matrix affect short term and long term properties
CONCRETE: 21st Century Superhero - Building a sustainable future London, 22-24 June 2009
FRP products
CONCRETE: 21st Century Superhero - Building a sustainable future London, 22-24 June 2009
Applications
CONCRETE: 21st Century Superhero - Building a sustainable future London, 22-24 June 2009
Applications
CONCRETE: 21st Century Superhero - Building a sustainable future London, 22-24 June 2009
Where we are!• Huge diversity of Commercial Products• FRP reinforcement market is growing
Internationally• First Generation Design Guidelines in
Europe, North America and Japan• Need for training Engineers• Need for testing standards
CONCRETE: 21st Century Superhero - Building a sustainable future London, 22-24 June 2009
fib bulletin 40• fib TG 9.3• En-Core Marie Curie
RT Network
CONCRETE: 21st Century Superhero - Building a sustainable future London, 22-24 June 2009
Main Design Issues
CONCRETE: 21st Century Superhero - Building a sustainable future London, 22-24 June 2009
Serviceability limit State• Limit on concrete and FRP stress; creep,
stress corrosion, durability• Deflection limitations same as for steel RC
• Eurocode equations OK, new dimensioning rules
• Crack width limitations can be relaxed• Strain based equations OK
CONCRETE: 21st Century Superhero - Building a sustainable future London, 22-24 June 2009
• Basic principles of section analysis apply• Concrete crushing or FRP rupture failure
• fib bulletin 40:- Concrete crushing -> Over reinforced- Afmin Mu >Mcr
- γm necessary?
Design for Flexural Capacity
CONCRETE: 21st Century Superhero - Building a sustainable future London, 22-24 June 2009
Design for Shear CapacitySteel RC relies on:
ys
w ds
fV
A⋅=
V = Vc + Vs
V
ρw
Vs
Vc
CONCRETE: 21st Century Superhero - Building a sustainable future London, 22-24 June 2009
ff
s
EA
E⋅
Maximum allowable strain
0.25% -> 0.45%
Design for Shear CapacityStrain Approach:
CONCRETE: 21st Century Superhero - Building a sustainable future London, 22-24 June 2009
The tensile strength of FRP bars is largely reduced when subjected to a biaxial state of stress
0.3bfb fu fu
b
rf f fd
α
= + ≤
rb is the radius of the bend in the bardb is the nominal diameter of the FRP barffu is the design strength of a straight portion of the bar
rb
Failure of shear links
CONCRETE: 21st Century Superhero - Building a sustainable future London, 22-24 June 2009
Concrete
Failure interface in resin
Bar fibers
Bar resin Failure interface in concrete
BondFailure Mechanisms
CONCRETE: 21st Century Superhero - Building a sustainable future London, 22-24 June 2009
Bond
CONCRETE: 21st Century Superhero - Building a sustainable future London, 22-24 June 2009
Bond and Tension Stiffening• Design equations (modified from steel)
Research required• Testing• Models• Effect on Tension Stiffening
CONCRETE: 21st Century Superhero - Building a sustainable future London, 22-24 June 2009
Design Philosophy Issues• Different predominant failure mode
• Influence of Partial safety factors; failure type• Safety levels
• Structural reliability of FRP RC elements is variable
• Resistance capacity margins• Is there a hierarchy? Should there be?
CONCRETE: 21st Century Superhero - Building a sustainable future London, 22-24 June 2009
Resistance Capacity Margins
CONCRETE: 21st Century Superhero - Building a sustainable future London, 22-24 June 2009
Design Philosophy• More economic design• More reliable design• Defined resistance
capacity margins• Can accommodate
innovation
CONCRETE: 21st Century Superhero - Building a sustainable future London, 22-24 June 2009
Concluding remarks• Use of FRP reinforcement on the increase• First generation of design guidelines exist• Second generation being developed