United Statessupport For Upgrading Existing Rc Structures

It is well-known that many reinforced concrete columns including particularly those RC columns constructed prior to the 1970s have been reinforced with an inadequate amount of transverse steel reinforcement which provides inefficient confinement to the concrete core or lateral restrain to the longitudinal reinforcing bars. Since the FRP composites owe some of the extraordinary properties such as high strength-to-weight ratio and excellent corrosion resistance, the use of externally bonded FRP composites has significantly increased in the construction industry. As confinement jackets, using FRP techniques is nowadays become one of the most popularly innovative confining means for upgrading existing RC structures. Therefore, several experimental studies have been carried out to date, such as on retrofitting or strengthening those structures with FRP systems, for example. In case of rarely sever seismic loads, establishing an axial stress-strain model considering cyclic axial compressi ve load is, in turn, imperative for simulating FRP-confined RC columns subjected to earthquake loads and performing a proper seismic design of such FRP-jacketed RC Columns, which are typically subjected to both axial and lateral force Wang et al.(2012). A uniaxial stress-strain model can be developed from laboratory testing results on axially loaded concrete columns confined with fiber-reinforcement polymer (FRP) composites and can then be applied as the constitutive law for confined concrete