Presentation Overview

1. Introduction

2. Laboratory validation of CFRP bars

3. Externally post-tensioned CFRP system

4. Structural implications of EPT system configuration 4. Structural implications of EPT system configuration

5. Conclusion

6. Reference

1.Introduction

1δ

2δ

External Force

3.Externally post-tensioned

CFRP bar system

Fig. (a) schematic of base configuration(b) live-end anchor for 12.7 dia mm bar.

Externally post-tensioned CFRP system

Fig. Trial field installation onto soffit of reinforced concrete slab.

2.Laboratory validation of CFRP bar

assembly

Sample ID

Failure load,

Fu (kN)

Tensile strength,ffu = Fu /Ab (Mpa)

Table: Uniaxial tensile test results

1 228.8 1806.6

2 261.8 2067.1

3 223.0 1760.9

4 235.1 1856.7

5 249.6 1970.6

Mean 239.7 1892.4

4.Structural implications of EPT

system configuration

� single-span member with EPT system:

(a) straight bar scheme with PT force applied at live end; and

(b) profiled bar scheme with extendable mid span deviator.

PT force and bending moment

components

1,pδ, 1 &sδ

2,pδ

3,pδ

Structural efficiency and effect of

boundary conditions

3

,

1

p p i

i

δ δ=

=∑

δ δ=

� Efficiency Ratio

, 1s sδ δ=

pE

sR

δδ

=

Structural efficiency and effect of

boundary conditions

2

2

1 (3 4 )cos ( ) 2 sin ( )

3(1 4 )ER k

µ µα λ α λµ

− −= + ×−

For Simply supported case:

2cos ( ) 2 sin ( )

3(1 4 )ER kα λ α λ

µ= + ×

−

21 4 (3 4 )cos ( ) 2 sin ( )

24 (1 2 )ER k

µ µα λ α λµ µ

− −= + ×−

For Fixed supported case:

Beam with simple supports

Beam with rotational end

constraints

Beam with rotational end

constraints

5.Conclusion� Reduces deflection in flexural members

� More effective than EB FRP System-cost effective

� Profiled bar scheme – clearance limitation, cost-benefit considerationbenefit consideration

� Applicable to structural rehabilitation of timber, steel bridges

6.Reference� “Flexural behavior of continuous steel girder with external

post-tensioning”, Journal of Constructional Steel Research

� “Unbonded CFRP Bar System for External Post-Tensioning”, American Composites Manufacturers Tensioning”, American Composites Manufacturers Association, COMPOSITES & POLYCON 2007, October 17-19, 2007,Tampa, FL USA

� Validation of externally post-tensioned carbon FRP bar system for rehabilitation (http://www.rb2c.miami.edu/Events/POSTERS-IAB_meeting-Oct12-13-2007.pdf)

Deviator� R=1900mm, � UHMW Polyethylene

Fig. schematic of base configuration

Stainless steel anchor for 12.7 mm dia bar