Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures

Description

The strengthening or retrofitting of existing concrete structures to resist higher design loads, correct strength loss due to deterioration, correct design or construction deficiencies, or increase ductility has traditionally been accomplished using conventional materials and construction techniques. Externally bonded steel plates, steel or concrete jackets, and external post-tensioning are just some of the many traditional techniques available. Composite materials made of fibers in a polymeric resin ,also known as fiber-reinforced polymers (FRPs), have emerged as an alternative to traditional materials for repair and rehabilitation.

For the purposes of this document, an FRP system is defined as the fibers and resins used to create the composite laminate, all applicable resins used to bond it to the concrete substrate, and all applied coatings used to protect the constituent materials. Coatings used exclusively for aestheticreasons are not considered part of an FRP system. FRP materials are lightweight, noncorrosive, and exhibit high tensile strength. These materials are readily available inseveral forms, ranging from factory-made laminates to dryfiber sheets that can be wrapped to conform to the geometry of a structure before adding the polymer resin. The relativelythin profiles of cured FRP systems are often desirable inapplications where aesthetics or access is a concern.

The growing interest in FRP systems for strengthening andretrofitting can be attributed to many factors. Although thefibers and resins used in FRP systems are relatively expensivecompared with traditional strengthening materials such asconcrete and steel, labor and equipment costs to install FRPsystems are often lower (Nanni 1999). FRP systems can alsobe used in areas with limited access where traditionaltechniques would be difficult to implement.