1. Rehabilitation of insufficient anchorage bar
lengths according to EN 1998 and the
Greek rehabilitation code KAN.EPE
Andreas Kalantzis / Civil Engineer

2. Anchorage bar length
 Is the required reinforcement bar length in order to transfer
safely the forces (axial, moment, shear) from one bar to
another without failure of the concrete – steel interface.
Imposed:
 By the steel industry(reinforced bar with length >10 m is
difficult to attach).
 In order to installed and transferred properly to the site.
 Usually encountered outside the critical zone of a column .

3. Rehabilitation of insufficient anchorage bar lengths
 Failure mechanism: The concrete is unable to receive and
transfer the forces/stresses and it cracks allowing the
reinforcement bar to slide (in a non ductile type of failure).
 Main object: The enforcement of an outer confinement that
will create compression stresses to the element in concretes
attempts to enlarge with tensile stresses.
A non destructive method is the use of FRP materials(fibre
reinforced polymer).

4. Fibre Reinforced Polymer materials(F.R.P)
 Advance and compose materials that consists of a
polymer(epoxy)matrix reinforced with fibers.
 Carbon, aramid and glass fibers.
 Advantages : extremely high tensile resistance, durability in
corrosion, low self weight, easy and rapid attachment.
 Disadvantages: notable cost of persuasion, poor performance
in high temperatures, zero ductility.

5. Stress – Deformation Diagram

6. Composite materials: Carbon, Aramid, Glass

7. ΚΑΝ.ΕPΕ 2012
ΚΑΝ.ΕPΕ
§8.2.1.2 figure. 8.3
In case of a constant cloak made from frp materials the ratio
Αj/s is the required thickness tj of the cloak.

8. ΚΑΝ.ΕPΕ 2012
 γrd=1.5 : safety coefficient for the uncertainty of the simulation .
 : the total area of reinforcement bar.
 : is the enforced design axial stress of the confinement
elements.
 λs : coefficient that describes the contribution of the all ready
attached(the insufficient)anchorage bar length. It is advised to be taken
λs = 0.

9. ΚΑΝ.ΕPΕ 2012
 ls : the reinforcement bar length
 : bf the wide of friction area along the crack of the
anchorage bars and Β is the wide distribution
of the total shear force that delivers the axial force from
the frp material material confinement( for c / ds ≤2
the value of β is near 1.0).
 μ : friction factor that depends on the magnitude of the compression
stresses between the crack interface as well from the acceptable sliding of
the bar. μ takes values from 0,4 to 2,0. Luck of data someone can consider
μ=1,0 .

10. Notations of ΚΑΝ.ΕPΕ 2012
Για τη εφαρμογή της τεχνικής πρέπει :
 The attached(insufficient) anchorage length ls should be grater than
0.30 lso and 15 ds
 The length of the element in which we will apply the confinement should
have at list the length of the critical zone and no less than 1,3 ls ή 0.60 m .
 Thickness t j ≥ 25 mm
 εjd= √2 wd / b , where wd =0.6 sd
2/3 while sd 0.3 for performativity
level Α and 0.4 for Β while C, b = (b1 +b2)/2 .

11. Example according to ΚΑΝ.ΕPΕ 2012
Material: Sika Wrap 600C/120 : tj=0.337mm ,E=242GPa , perf. Level Β
Φ18 , fyk=330 Mpa , 400mm x 200mm , Ab =π182/4=254.5mm
lso =Φ fyd/4 fbd= 782mm , 0,3x782=234.6mm , at least ls=210mm
ΚΑΝ.ΕPΕ
§8.2.1.2 , rel. 8.3
1.61mm/0.337mm=4.77 ≈ 5 layers
Για κ ≥ 4 layers , tj =ψ κ tj με ψ=κ-1/4 where ψ the reduced efficiency
coefficient of multi layering. ΚΑΝ.ΕPΕ
We are choosing 8 layers of material § 6.2.3

12. EN1998-3
According to §Α4.4.4(tightening of the bonds by overlaping the bars )of the Α
annex of ΕΝ 1998-3
( ΕΝ1998-3 , §Α.4.4.4 , Α.37 )
 σsw=0,001ρwEs
 For orthogonical columns D is the wide bW of the cross section§A.4.4.4(2)
 Εf is the modulus of elasticity for the frp material

13. EN1998-3
EN 1998-3 , §Α.4.4.4 , (Α.38)
 Α s the area of every reinforced bar that is been overlped.
 fyl the yield bound of steel that can be taken equal to the middle value,
multiplied properly with the so called trust coefficient CF ( ΕΝ 1998-3 §3.3 )
 p the perimeter of the column measured from the inner side of the longitudinal
reinforcement bar.

14. EN1998-3
 dbl the maximum diameter of the longitudinal reinforced bars
 c thickness of concrete cover.
 Ls the anchorage length
 n the number of the overlapped bars along p

15. Example according to EN1998-3
For orthogonical column: CFΕΓ3=1.0, c=30mm, tf=0.337mm , fyk = 330
400 6Φ18, Ef =242GPa
Φ 200
( EN1998-3 A.4.4.4 , A.37 )
1.1mm/0.337mm = 3 layers

16. Comparison
ΚΑΝ.ΕPΕ , § 8.2.1.2 , (8.3)
EN1998-3 , §A.4.4.4 , A.37

17. Conclusions
 The relation8.3 of ΚΑΝ.ΕPΕ proved conservative compared to relation
Α.37 of EN1998-3 and thus it gives grater values of material thickness.

 Bigger thickness of frp material leads to small number of layers.
 Performativity level Β and C ( ΚΑΝ.ΕΠΕ §8.2.1.2 , β , ii ) leads to bigger
values of deformation εjd .

18. End of presentation
Thank you