Services - Fiber Reinforced Polymers
Masonry Parapets Strengthened with Fiber Reinforced Polymer (FRP)
Reinforced Polymer (FRP) products offer a cost-effective system to strengthen masonry parapets.
Among the advantages of Reinforced Polymer (FRP) are:
- Increases out-of-plane flexural strength
- Increases in-plane shear strength
- Confines masonry units, resulting in monolithic action of all units
- Prevents secondary damage from falling debris
- Works as a waterproofing material
- Adds very little weight to the wall
- Increases wall thickness by less than 1/4in. (5 mm)
- Costs less than conventional methods
Concrete Beam Strengthened with Glass or Carbon FRP
Glass Fiber Reinforced Polymer (GFRP) or Carbon FRP is economical and efficient materials for strengthening concrete beams for flexure and shear. Among the advantages of GFRP and CFRP are:
- Increased flexural strength for both positive and negative moment regions
- Increased shear strength
- Increased stiffness at service loads
- Reduced cracked widths for enhanced durability and corrosion resistance
- No reduction in overhead clearance (e.g. in parking garages)
- Lower cost than conventional methods
Because the moment capacity of a section is the couple resulting from the tensile and compressive forces, FRP can be applied to the tension face of the beam to increase the tension force. In most case, the deck or floor slab does have sufficient compressive strength and does not require strengthening. However, if needed, FRP can also be added to the compression face of the beam. In some of the pioneering studies carried out in the late 1980s by the principals of QuakeWrap, Inc, it was clearly shown that improper epoxies can result in FRP retrofits that add little to the strength of the beam. These studies formed the basis for several years of additional R&D that resulted in the development on QuakeBond™ epoxies.
Tests of reinforced concrete beams strengthened with glass and carbon FRP have demonstrated that when appropriate epoxies are used, failure will not take place in the bond line; instead, similar to reinforced concrete flexural members, one can proportion the design such that failure is reached in concrete after yielding of the longitudinal steel reinforcement. This is particularly important because the yielding of steel can provide the necessary ductility that lacks in the behavior of FRP products.
Seismic Repair and Strengthening of Concrete Columns with Glass or Carbon FRP
Reinforced Concrete columns or bridge piers can be efficiently strengthened with Glass FRP (GFRP) or Carbon FRP (CFRP). Older (pre-1970s) columns have two major shortcomings; they are inadequately confined (usually a No. 3 or 4 tie placed at a spacing of 12 inches) and the ends of the ties are not properly anchored in the core region. During an earthquake, the ties open and allow the longitudinal steel to buckle, leading to failure of the column.
Glass FRP and Carbon FRP can provide significant lateral confinement for concrete columns or bridge piers. While spiral columns have in general performed well in past earthquakes, the above shortcomings have resulted in failure of many tied columns such as the one shown on the right.
The solution is to externally confine the column. External confinement increases the strength of the concrete, but more importantly for seismic applications, the strain at failure of the concrete (i.e. ductility) increases significantly. Among the advantages of retrofitting columns with Fiber Reinforced Polymer (FRP) are:
- Increases Ductility
- Increases Shear Strength
- Improves Bond in Starter Bars
- Conforms to Various Cross Sections
- Requires Minimum Access
- Costs Less than Conventional Methods
Slabs Strengthened with Fiber Reinforced Polymer (FRP)
Glass or Carbon FRP is a cost-effective system for strengthening concrete floors and decks or correcting design and construction errors that have led to excessive deflection and sag in the slab. The case history below highlights one such application.
Among the advantages of Fiber Reinforced Polymer (FRP) for strengthening slabs are:
- Increased flexural strength for both positive and negative moment regions in the slab
- Increased slab stiffness and reduced deflections at service loads
- Reduced crack widths for enhanced durability
- Covering a fraction of the slab surface with FRP may be sufficient for strengthening the entire slab
- No reduction in overhead clearance is caused by application of FRP (e.g. in parking garages)
- Lower cost for FRP compared to strengthening with conventional methods (e.g. epoxy injection in cracks)
Glass or Carbon FRP are very effective in repair and strengthening of slabs and decks. Because the moment capacity of the slab or deck is the couple resulting from the tensile and compressive forces, FRP can be applied to the tension face of the beam to increase the tension force. In most cases, the deck or slab has sufficient compressive strength and does not require strengthening. However, if needed, FRP can also be added to the compression face of the beam as a part of strengthening and repair. In some of the pioneering studies carried out in the late 1980s by the principals of QuakeWrap, Inc, it was clearly shown that improper epoxies can result in retrofits that add little to the strength of the beam. These studies were the basis of several years of additional R&D resulting in the development of QuakeBond™ epoxies.
Strengthening of Steel Bridge Girders with Carbon FRP
Carbon Fiber Reinforced Polymer (CFRP) is an economical and efficient system for flexural strengthening of steel bridge girders. Among the advantages of repair and strengthening of steel beams and girders with FRP are:
- Increased flexural strength in the steel girder for both positive and negative moment regions
- Restores steel girder capacity after loss of tension flange area due to corrosion
- Increased stiffness of the steel girder in both elastic and plastic response
- Eliminates stress concentration in the steel girder due to welding
- Improved fatigue behavior of steel bridge girder (after retrofit with FRP)
- Lower cost than conventional methods
The feasibility of strengthening of steel bridge girders with carbon FRP was demonstrated through an extensive research study at the University of Arizona. The girders were constructed using W14x30 steel sections and as shown in the above photos, spanned 16 feet (4.8 m) during the test.
Carbon Fiber Reinforced Polymer (CFRP) also improves the fatigue behavior of the structure; the CFRP retrofitted beams could resist 2½ – 3½ times more cycles of loading compared to the cracked bridge steel girders that were not retrofitted with carbon FRP.
Repair and Strengthening of Tanks with Carbon Fiber Reinforced Polymer (CFRP)
Carbon FRP offers an ideal solution for repair and strengthening of tanks and silos that are damaged by corrosion. In many cases, leakage of these tanks can be stopped by means of carbon or glass FRP.
Moreover, by applying carbon or glass FRP, repair and strengthening of the tank or silo can be achieved to levels that exceed original design strength. This is particularly interesting since such strengthening or repair with FRP will allow additional loads to be imposed on the FRP-retrofitted tank.
Fiber Reinforced Polymer (FRP) is an economical and efficient material for repairing and preventing corrosion and/or leakage problems in metallic, reinforced concrete and fiber glass tanks and silos. Among the advantages of Fiber Reinforced Polymer (FRP) for repair and strengthening of tanks and silos are:
- FRP provides a continuously bonded liner on the tank's inner and/or outer surfaces that forms an air-tight seal that effectively prevents corrosion and leakage and strengthens the tank or silo.
- FRP increases the flexural and shear strength of rectangular tanks.
- FRP increases the longitudinal and hoop strength of circular and cylindrical tanks and silos.
- FRP provides electrical insulation for tanks used as electrolytic cells in the mining industry.
- FRP resists high temperatures of contained substances when bonded with heat-cured resins.
- FRP resists highly corrosive substances when coated with high chemical resistant toppings.
- When installed on the inner surfaces, technicians can access through openings (manholes) and no excavation of underground tanks is required.
QuakeWrap has developed a special patent-pending procedure for repair and strengthening of electrolytic tanks in the mining industries with carbon and glass FRP. Among unique features of this FRP system is a special fabric that is resistant to damage due to falling electrode plates.
The installation procedure of QuakeWrap FRP to repair and strengthen tanks and silos is simple and involves basically cleaning and patching of tank surfaces, application of a resin tack coat (QuakeBond J201-TC) that allows for the QuakeWrap fabric to adhere on vertical and overhead surfaces, saturation of the fabric with the proper saturating resin and application over the tack coat.
