FRP provides an efficient alternative and advantageous retro
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Several recent destructive earthquakes have alerted the society the urgent need to upgrade existing older structures to modern seismic design standards in regions with high seismicity. For reinforced concrete columns, problems needed to be solved using retrofit measures include the lack of flexural strength and ductility due to improper design of longitudinal reinforcement lapsplices, poor confinement of potential plastic hinge zones, the lack of shear strength, as well as the inadequate design of column to beam or footing connections, etc.
The conventional retrofit measures include external confinement of the column by adding reinforced concrete layers, the use of steel cables wound around the existing column and covered by concrete, and the use of steel jackets confining the existing columns (Rodriquez and Park 1991; Chai et al. 1991). Steel jacketing can be considered as a tubed column system, where the tube or jacket is detailed in a way to function as transverse reinforcement, as shown in Figure 1. Although steel jacketing has been widely used in practices in California and elsewhere (Priestley et al. 1994), it is relatively time consuming, thus can cause traffic disruption, and susceptible to degradation due to corrosion. The society is looking for other alternatives to improve and speed up the retrofitting process for the vast number of existing,structurally deficient structures throughout the world.
FRP provides not only an efficient alternative, but also an advantageous retrofit measure.
