Fiber reinforced polymer (FRP) composite systems, consist of fibers embedded in a polymeric matrix. They are used for Flexural and Shear strengthening of reinforced concrete (RC) members. Since the late 1980s, there has been a frequent increase in the use of FRP systems. The number of projects in which FRP are used have increased rapidly. Externally bonded FRP are used for strengthening beams, columns, slabs, tunnels, pipes, trusses etc. These are also used to strengthen masonry, timber, steel structures.
FRP was basically used as an alternative to the strengthening technique of attaching/bonding steel plates. Initially, this retrofitting technique was utilized in the 1980s in both Europe and Japan.
FRP are commercially available in the form of sheets that can be bonded to the outer surface of concrete members, therefore, they are also termed as External reinforcement. These are nowadays used as proper construction material for the strengthening of Beams, slabs, columns etc.
Types Of FRP Systems
There are two types of FRP sheets that are commonly used
- Glass Fiber Reinforced Polymers (GFRP)
- Carbon Reinforced Polymers (CFRP)
FRP systems are used in several forms based on different load conditions, environment, structural members dimension and shape. Most commonly used forms in FRP systems are given below;
Wet lay-up FRP systems
In this system, FRP sheets are saturated with resin and cured at the site. These unidirectional fiber sheets having multidirectional fibers are attached to the concrete without any resin application. Extra heat may be required to achieve full cure.
Pre-cured FRP systems
These systems are available in variety of manufactured shapes such as laminated sheets, unidirectional strips etc. Concrete surface shall be finished properly to achieve the smoothness required for installation of pre-cured FRP systems.
Applications Of FRP System
FRP systems have various applications. Some of them are mentioned below
- Used for limiting the crack width under increased and loads.
- For designing concrete members having depth limitations.
- For providing confinement to concrete members.
- For Repairing the damaged structures (concrete beams, columns, slabs etc.)
- Retrofitting structures built with masonry.
- Resolving design problems and construction errors.
Advantages Of FRP Concrete System
Many successful applications of FRP systems for rehabilitation of damaged structures have been found up till now. Some of the advantages that make FRP a preferable retrofitting material are as follow
- Higher Durability
- Higher Corrosion resistance
- Cost effective and requires less maintenance.
- Higher Stiffness-to-weight ratio (1 & 3 for glass and carbon respectively)
- Higher Strength-to-weight ratio (15 & 35 for glass and carbon respectively)
- Greater Ductility, therefore, gives warning before failure.