Fiber Reinforced Plastic(FRP)

1. Introduction:

Throughout history, earthquakes have caused severe losses whether in human lives or economic values (money, property...). However, existing RC structures that were designed and constructed based on old codes often showed low resistance to lateral loads, insufficient energy dissipation, rapid strength deterioration and improper hinging mechanisms during earthquakes.

For those structures, many ways of rehabilitation, repairing and retrofitting have been introduced. The traditional method of repairing or strengthening of RC columns is by steel jacketing, exterior coupled shear walls, concrete infilled shear walls, thin layers of heavily reinforced concrete or pre-tensioned steel cables covered with thin layer of concrete. These Methods involve difficult implementation procedures and a high cost. Then, FRP was introduced to the market.

2. A brief history of FRP:

The first use of glass fiber reinforced polyester composites was in the aircraft industry during the 1940s. This was followed some years later by the first non-military application in the marine sector, where FRP proved a complete innovation making a revolution in the way boats were built.

The development of fiber-reinforced plastic for commercial use was being extensively researched in the 1930s. In the UK, considerable research was undertaken by pioneers. It was particularly of interest to the aviation industry.

Carbon fiber production began in the late 1950s and was used, though not widely, in British industry beginning in the early 1960s. Repair and rehabilitation of reinforced concrete (RC) columns was the first successful applications of FRP composites that were initiated in early 1990.

This application was extended to other applications including: RC beams floor slabs bridge decks beam-column joints pipes tanks shear walls

3. Definition:

Fiber-reinforced plastic FRP (also fiber-reinforced polymer) is a composite made of high-strength fibers and a matrix for binding these fibers. The fibers are usually glass, carbon, aramid, or basalt.

FRP systems have significant advantages over classical structural materials including: low weightcorrosion resistance ease of application

4. Usage:

FRP is particularly suitable for structural repair and rehabilitation of reinforced concrete structures. FRPs are commonly used in: aerospace automotive marine construction industries ballistic armor

It is possible to increase the strength of structural members even after they have been severely damaged due to loading conditions.

STRUCTURAL APPLICATION OF FRP MATERIALS

FRP laminates and sheets FRP profiles and

panels

FRP rebars

Field of application of FRP materials

Internal reinforcement

of RC structures

External strengthening

of RC structures

Hybrid structures

(with traditional)

Fully- composit

e structure

s

Field of application of FRP materials

FRP REBARS – GEOMETRY AND PROPERTIES

• Constitution: polymer matrix (vinylester) and rovings (axial fibre reinforcement)

• Available diameters: 6 to 36 mm• Surface finishing: a) ribbed;

b) sand coating; c) exterior wound fibres and sand coating

• Geometry: a) straight; b) with anchorage heads; and bent c) in U or d) hooked

Schöeck

ACI

Reinforcement of bridge deck

Aquaculture (Acuinova, Mira)

FRP REBARS – APPLICATIONS

Repair of maritime structures, dock and pier

FRP STRENGTHENING SYSTEMS - TYPOLOGIES

• Laminates: unidirectional precured (carbon) fibre strips, adhesively bonded with epoxy adhesive.

• Sheets: uni/multi-directional mats of continuous (carbon) fibres, moulded and cured in situ, impregnated and bonded with an epoxy matrix.

CFRP sheets

CFRP laminates

Bettor

Bettor

NOTE: There are also rebars and cables/tendons

Laminates:

- E = 165 to 300 GPa

- u = 1500 to 3000 MPa

- u = 0,5 a 1,7%

Sheets:

- E = 240 to 640 GPa (typically, 240 to 300 GPa)

- u = 2500 to 3000 MPa

- u = 0,4 a 1,55 %

FRP STRENGTHENING SYSTEMS - PROPERTIES

16/50

Flexural strengthening of beams and slabs

Shear strengthenig of beam

Column strengthening

FRP STRENGTHENING SYSTEMS - APPLICATIONS

17/50

Flexural and shear

strengthening of beam

(confinemen)

Strengthen the bridge for shear and flexural forces.

Tanks

Hardcore system

Kansas system

FRP SANDWICH PANELS – CONSTITUTION

Commercial systems

FRP sheet

• FRP outer skins - thin, stiff, resistant

• Core - thick, light, more flexible, less resistant (rigid foam, balsa wood, etc.)

• Adhesive

Adhesive

Core

Sandwich panel

FRP sheet

5. Installation Procedure:Applying FRP wraps to structural concrete isn't difficult, but does require experience. One hundred percent of the quality is due to workmanship. All of the FRP strengthening system manufacturers consulted require some level of expertise in an installer. 

Step-1: Surface preparation, starting with simply cleaning

the concrete to remove any chemicals or dirt. For most applications, this is followed by water blasting to achieve a roughened surface profile.

However, there are two types of applications to consider: bond critical and contact critical. Bond-critical applications rely completely on the bond of the material to the surface of the concrete to transfer the stresses. Contact-critical applications are where the FRP is bonded to itself and creates confinement of the structural member. An example of a contact-critical application is a column where the FRP wraps completely around onto itself.

Step-2: Any defects in the concrete are repaired—holes and

cracks filled with epoxy. Sharp edges, corners, and other form lines should be

smoothed to prevent stress concentrations.Step-3: placement of the saturated fiber fabrics. Fiber sheets come in rolls that are typically 24 or 48

inches wide. Prior to application, it must be saturated with resin. Resins are color-coded two-part materials that are premeasured to simplify mixing.

-For a small job, you can make a temporary table and pour the saturating resin over the fabric and work it in with a squeegee, while for larger jobs saturating machines pass the fabric through a vat of resin and run it between two steel wringer rollers to force the resin.-The installer needs to be sure to apply the fabric in the correct orientation, in the correct locations, and in the correct number of layers or plies. The fabric can be placed in up to three layers.

Step 4: A topcoat is applied next that can handle pH 2 to 12. Fire protective coatings often are applied last and four-hour ratings

can be achieved. Curing takes about 24 hours, which can be accelerated with

temperature.Step 5: Testing after installation often is required with the most common

tests being a tap test and a pull-off test to check the bond of the epoxy to the concrete surface.

Tap tests are just like hammer sounding for concrete delamination. Pull-off tests usually specify a bond strength of 200 psi.

Glass reinforced polymers are strongest and most resistive to deforming forces when the polymers fibers are parallel to the force being exerted, and are weakest when the fibers are perpendicular.

6. Advantages and special properties of FRP:

The most important advantage is that: FRP has a high s/w ratio. FRP doesn’t show any yielding or plastic behavior. FRP composites have tensile stiffness lower than that of steel Resistance to corrosion so it can be utilized on interior and exterior structural

members in all almost all types of environments They are devoid of any magnetic field and can offer considerable resistance to

electric sparks, then it is a very good option for the power industry FRP is characterized by the ease of application since heavy equipment is not

needed for the rehabilitation hence social effects are witnessed.

The other exclusive advantages of fiber reinforced plastics include:Commendable thermal insulationStructural integrity, and fire hardness along

with UV radiation stability Resistance to chemicals and other corrosive

materials.

Vs. timber:

When it comes to structural applications, fiberglass reinforced plastic offers significant advantages compared to timber. Unlike wood, fiberglass shapes won’t warp, rot or decay from exposure to moisture. They’re resistant to corrosion, insects, mold and mildew. they don’t need environmentally hazardous coatings or preservatives to deliver

exceptional durability. Stronger and more rigid than structural timber Corrosion, rot and insect resistant Consistent in strength, appearance and quality from piece to piece 

Vs. steel:  Fiberglass reinforced plastic is highly corrosion resistant. So unlike steel, it won’t rust when it’s exposed to harsh weather and chemicals. It’s also nonconductive and impact resistant. Pound for pound, FRP structural members are stronger than many steels in the

lengthwise direction weigh up to 75% less. The strength of steel at 1/4 the weight Simple fabrication with standard tools (no welders or cutting torches) Molded-in color and resin options, including fire retardant

Vs. aluminum:  Fiberglass-reinforced polymer offers substantial advantages compared to

aluminum extrusions. Unlike aluminum: Fiberglass shapes won’t corrode and are non-conductive. FRP has low thermal conductivity, so it’s a good insulator. FRP pultrusions won’t deform under impact.  Superior resistance to a broad range of chemicals EMI/RFI transparency (transparent to radio/radar/antenna transmissions) Light weight with high strength

7. Case study:

In this case study FRP composite has been used to retrofit columns. FRP that are applied on columns can improve many properties of the columns. We are interested in structural properties such as: Axial Flexural shear load capacities ductility.

Problem: Deficiencies and failure mechanism should be understood for proper understanding of the design system, then the needed reinforcement can be determined

Structural deficiencies should be either due to improper design or detailing. The latter includes: Lack of structural walls or moment resisting frames Lack of redundancy in the structural system. Irregularities in the plan or elevation. Presence of soft stories. Strong beam-weak column joints. Inadequate transverse reinforcement bar Short overlap lengths of spliced joints.

Deficiencies cause failure and failure in column due to seismic loading has three different mechanisms: Shear failure which is the most critical due to excessive inclined cracking. Confinement failure due to excessive flexural cracking. Lap splices failure due to insufficient splice length and debonding.

When rehabilitating columns, all potential failure should be taken into consideration and avoided.

Strengthening one part of the column may shift the failure to another part so it is better to confine the entire length of the column.

Flexural plastic hinge contribution: During seismic loading, plastic hinges form at maximum moment locations in the case of columns. These hinges should be able to sustain large inelastic rotations to avoid sudden failure confining the columns at critical locations is the most effective way to improve the rotation capacities.

Results:A performed nonlinear finite element analysis of control and FRP- wrapped RC large sized columns subjected to axial and cyclic lateral loadings. The FRP fabric in the potential plastic hinge location at the bottom of the column showed significant improvement in both strength and ductility capacities,energy dissipation and the FRP jacket delayed the degradation of the stiffness of reinforced concrete columns.

These studies show that the FRP composites prove to be efficient as retrofit materials in increasing 1. the lateral load 2. drift capacity And reducing 3. the damage in non-seismically designed RC

columns.

Test procedure:

Specimens are placed in the grips of a Universal Test Machine at a specified grip separation and pulled until failure. For ASTM D3039 the test speed can be determined by the material specification or time to failure (1 to 10 minutes). An extensometer or strain gauge is used to determine elongation and tensile modulus. Depending upon the reinforcement and type, testing in more than one orientation may be necessary.

Specimen size:The most common specimen for ASTM D3039 is a constant rectangular cross section, 25 mm (1 in) wide and 250 mm (10 mm) long.

ACI 440.3

Pullout bond test:This test method is intended to determine the bond behavior for material specifications, research and development, and quality assurance. The bond behavior will be specimen configuration dependent, which may affect both analysis and design. The primary test result is the bond strength of the specimen to normal weight concrete, which is an important factor to be considered in the use of FRP bars as reinforcing bars or tendons.

Bending test for FRP

This test method is intended to determine the flexural tensile data of bent FRP bars for material specifications, research and development, quality assurance, and structural design and analysis. The primary test result is the bent tensile capacity of the specimen under a specific loading and environmental condition.

9. Conclusion:

FRP systems have significant advantages over classical structural materials It’s usage needs expert knowledge It’s not cheap as other materials It can be applied on different concrete members Can be the unique solution for certain problems

http://www.structuremag.org/?p=8643 http://info.craftechind.com/blog/bid/393452/A-Beginner-s-Guide-to-Fiber-

Reinforced-Plastics-FRP-s http://info.craftechind.com/blog/bid/369492/Fiber-Reinforced-Plastic-FRP

-in-Action http://bedfordreinforced.com/why-our-material http://www.intertek.com/polymers/tensile-testing/matrix-composite/ http://www.radyab.co/content/media/article/4403R_04_0.pdf https://en.wikipedia.org/wiki/Fibre-reinforced_plastic

References

Presented by: Said Waked 201302158 Abdalla Mezher 201200567 Mohammad Abou Kayss 201300213

Bilal Al Khatib 201300579 Mohammad El Sayed 201300149 Mohammad Younes 201300407 Said Smaili 201203959

Thank You