Fiberglass Reinforced Polymer (FRP) Rebar

 
Fiberglass rebar  is a structural spiral wrapped fiberglass reinforcing rod which is corrosion resistant, non-conductive and lightweight while it is one-fourth the weight of steel rebar.  It more closely matches the characteristics of wood for modulus of elasticity, expansion and contraction, and condensation than does typical steel reinforcing rod.  

The Modulus of Elasticity of FRP rebar from the test results is 7.86 x 10 psi, that of steel 30 x 10 psi. In other words, for the same shape and same load, FRP will deflect, elongate, or compress approximately five times as much as steel.

USES

For making load bearing connections, pinning and reinforcing wood and concrete elements.  Typical applications include attachment and reinforcement of rafters, trusses, purlins, framing members, beams, sills, columns, logs, timbers, etc.  It can be used for casting wood and concrete elements and to replace steel rebar in concrete slabs, forms and beams.  Fiberglass rebar is most often used in conjunction with  Epoxy Adhesive for attaching the rebar to the elements and the elements to one another.  

Does the FRP Rebar have a fire rating?

No. We have a resin rated at 500°F Heat Distortion
Temperature. We think the rebar will show very little loss
in physicals up to 700° F. to 800° F.

Design Hints

1. Use Working Stress Method of Design
2. Use a Modular Ratio of N=2 (for 4,000 psi concrete)
3. Use a maximum allowable tensile stress of 18,000 psi
4. At spliced joints, use an overlap of 40 x bar diameter
5. Bond Strength to concrete is approximately equal to that of steel rebar
6. Transverse shear strength is 30,000 psi

What is the E value of the FRP rebar?

Per the University of Arkansas Test result: 7.86 x 106 psi

How does the Modulus of Elasticity affect design planning?

The high Ultimate Strength to a low Modulus of Elasticity (E) Ratio, deflection is the limiting design factor. Deflection is a function of Modulus of Elasticity, all other factors being equal (i.e. shape).

Does the Modulus of Elasticity change with the different sizes of FRP rebar?

No. It is an inherent physical property of the material.

What is the mode of failure?

Glass does not yield. Yield strength and ultimate strength are the same point. Glass is a brittle, not a ductile material.

How does the flexibility, or low Modulus of Elasticity, affect design?

The designer deals with deflection by using more FRP reinforcement than he would in designing for steel, i.e., more or larger bars; or by using deeper beams, etc.

What form is the Stress/Strain curve?

The Stress/Strain curve is a straight line to failure, at a slope equal to E, up to Ultimate Strength of approximately 150,000 psi (approximately 4 times ASTM Grade 40 steel)

What is the Fatigue and Stress/Strain Relationship?

The University of Arkansas test report was based on several hundred tests for which stress/strain curves were plotted. We know that FRP does not fatigue when stressed to no more than 1/2 of its ultimate strength. It does not yield as do other materials such as steel. Ultimate strength and yield strength are the same. It would be extremely unlikely that FRP rebar would be designed to working load of more than 1/4 of Ultimate Strength (approximately 160,000 psi)

What is the Ultimate Strength for the different sizes of Rebar?

"Ultimate Strength" refers to per unit values. It is a physical property of the material itself that applies to all sizes and shapes into which the material may be formed. Tests indicate that the Ultimate Strength of the FRP rebar is approximately 160,000 psi maximum. The "breaking strength" of various sizes of rebar can vary in inverse relation to bar size - from 160,000 psi for smaller sizes, to 100,000 psi for larger bars.

How do you use FRP rebar in beam and slab design?

The designer is simply using a material with different physical properties. As a result of the difference in the physical properties (in this case a lower value of E), he will arrive at different amounts of reinforcements, beam sizes, column dimensions, etc. than if he were designing in other materials.

How do you tie the bars together?

Cable ties of plastics clips.

Can the FRP rebar be bent by the customer?

No. Resins are cross-linking thermo-sets. Cure is a chemical reaction, not a change of physical state.
All ACI bends are available by manufacturer.

What is the life span of FRP rebar?

The FRP rebar has been in use for over 20 years, without any evidence of degradation.
Life expectancy of the FRP rebar is - forever!

What are the most efficient ways to cut FRP rebar?

With a hack saw, brick saw, or diamond chip saw.

Are there any special storing requirements?

No. FRP rebar will not rust. It is non-corrosive and is unaffected by electrochemical deterioration.
Storage of FRP rebar prior to placement will no cause deterioration.

How well does FRP rebar bond with concrete?

The FRP rebar is a deformed bar. Bonding is comparable to steel.

PROPERTIES  

Minimum Ultimate Tensile Strength:

140,000 psi (About Three Times Steel)
Tensile Modulus: 7.86 X 106 psi Average
Coefficient of Thermal Expansion: 5.5 X l0-6 in/in°F

0.067 Lbs./1n3 (About 1/4th That of Steel)

Continuous drawn glass roving saturated with vinyl ester resin.  A single strand, spiral wrapped around the exterior diameter to provide a spiral indentation in the bar providing maximum bonding and lock to epoxy, concrete or grout bedding.

SIZE AVAILABILITY