【正文】 icreinforced concrete jacket. Three specimens were retrofitted with FRP wraps and twomore specimens were retrofitted with steel jackets. In addition, six specimens wereretrofitted with a PCS reinforced concrete jacket, including two different thicknesses ofPCS. Nine specimens had the entire cross section of the base column and retrofit area simulated a retrofit condition when the applied load is distributed across the entirecross section. Five specimens had the cross section of only the base column loaded,which simulated a condition when the load is only applied to the original member. Threeother specimens had increased lateral reinforcement spacing with similar transversereinforcement strength per spacing. These specimens also had the entire retrofit and basecolumn crosssection loaded. RETROFIT OF EXISTING STRUCTURES Many structures have historically been constructed using reinforced concrete. Typicalordinary concrete consists of four constituents: gravel, sand, water, and concrete has some type of reinforcement, typically steel, bined withconcrete to produce a stronger system than plain concrete. Concrete is strong in pression but weak in tension. Tensile forces cause concrete to crack and eventuallyfail in a brittle manner at stresses significantly lower than the pression strength ofconcrete. Steel, or another type of reinforcement material, can be used to pensate forthe weak tensile strength of concrete. This system is referred to as reinforced concrete. As reinforced concrete ages, a variety of detrimental effects can occur. These includespalling, flaking, or cracking of the concrete, and subsequent corrosion of the reinforcingsteel. These occurrences can significantly affect the strength of structural displaying these adverse affects may be rehabilitated using an appropriateretrofit method. Retrofitting is typically done for two reasons: rehabilitation or strengthening. As previously discussed, rehabilitation is fixing the structural deficiencies of a damaged structure or structural member. This may be necessary for aging members that no longerdisplay the strength of the original design. Strengthening increases the loadcarryingcapacity of a structural member (Ersoy et al. 1993). This may be necessary if thesupported load is altered through the life of the structural member, or if current designstandards have more stringent reinforcement requirements. Additionally, structuralmembers in seismic regions may need to be upgraded to current seismic requirements. Retrofitting can be applied to any structural members, including beams and methods are traditionally utilized for retrofitting. These include concretejacketing, steel jacketing, and FRP strengthening (Wipf et al. 1997). Reinforcement forconcrete jackets can be provided by rebar reinforcement or welded wire fabric (WWF).Additionally, a relatively new product, Prefabricated Cage System reinforcement (PCS),is suggested as a possible reinforcement alternative for concrete jacket retrofits. PCS Benefits PCS reinforcement has some unique properties. The longitudinal and lateral reinforcement for PCS are located the same distance from the center of the member crosssection. This provides increased flexural capacity, using the same amount of steelas a traditional rebar system, and results in more efficient use of the reinforcing monolithic action of PCS eliminates separation of longitudinal and transverseeinforcement. Additionally, PCS reinforcement is spread in a planar configurationwhich offers greater confinement than rebar reinforcement, as displayed in Figure of the PCS steel determines the dimensions of the reinforcement confining the concre