Canada

NSERC Industrial Research Chair in FRP Reinforcement for Concrete Structures

Schematic drawing of sustained loading frames

Specimens under sustained loads

and alkaline solution at ambient

temperature

Fulcrum Weight

Frame base

1440mm

19

00m

m

Swivel head Lever arm

Pipe grip

FRP rebar

Outline of heating chamberSpherical nut

Plastic tube for environmental solution or concrete cylinder

Load calibrating system

Evaluate residual tensile characteristics of FRP barsunder various alkaline, temperature, and stress levels

Experimental set-up

Canada

NSERC Industrial Research Chair in FRP Reinforcement for Concrete Structures

Test specimens

Short and long-term properties of FRP bars

Canada

NSERC Industrial Research Chair in FRP Reinforcement for Concrete Structures

Experimental Program Test Parameters on GFRP Bars (sustained tensile stress)

Environmental Conditioning: � Alkaline (pH 13)

� De-ionized water

� Temperature –accelerating factor ( up to 65ºC)

Loading Conditioning:

� Sustained tensile loads (20 to 40% of UTS)

Exposure time- periods: 1, 3, 6 months, ...

Samples: More than 1000 have been tested

Short and long-term properties of FRP bars

Canada

NSERC Industrial Research Chair in FRP Reinforcement for Concrete Structures

Concluding remarks

• The tested GFRP bars performed very well

• Residual tensile strengths for conditioned specimens:

� In the magnitude range of the specified guaranteed ultimate tensile strength

� Higher than the specified design strength

( as recommended by ACI 440 design guidelines)

Canada

NSERC Industrial Research Chair in FRP Reinforcement for Concrete Structures

Research Objectives

�Creep strain with time

�Any Change in the Elastic Modulus?

�Effect of External Environment on Strain?

�Effect of the Applied Stress Level

Canada

NSERC Industrial Research Chair in FRP Reinforcement for Concrete Structures

Grip ends

Reservoir

GFRP bar (exposed portion)

V-Rod GFRP

bars used

Canada

NSERC Industrial Research Chair in FRP Reinforcement for Concrete Structures

Testing Scheme

38%

38%

25%De-Ionized Water

29%Alkaline Solution

Applied Stress

% Medium

∗

uf

� At room Temperature

� For 10,000 Hours

Canada

NSERC Industrial Research Chair in FRP Reinforcement for Concrete Structures

Lever arm

Pipe grip

FRP rebar

Load calibration system

1900 m

m

Reservoir

Frame base

W

Swivel head

1440 mm

Laboratory Set-up

Canada

NSERC Industrial Research Chair in FRP Reinforcement for Concrete Structures

Lower Bound Results!

Initiation of failure near splash zone

Stains at ends of the reservoir

Canada

NSERC Industrial Research Chair in FRP Reinforcement for Concrete Structures

Hours

Days

Strain in Alkaline Solution

3000

4000

5000

6000

7000

100 200 300 400 500

Strain

µεεεε

2400 4800 7200 9600 12000

29%

38%