【正文】 te. PCS reinforcement offers several additional benefits. Dimensions of the reinforcementare determined by the designer to produce any desired amount of transverse andlongitudinal reinforcement. This allows a great deal of flexibility and efficiency in thedesign process, as reinforcement choices are not limited to available stock , PCS reinforcement can be fabricated offsite and immediately placed for concrete casting without additional fieldwork, such as tying, cutting, or bending ofreinforcement, which prolong construction time. Offsite fabrication also provides anincreased level of quality control for the reinforcement. In PCS production, dimensionsand spacing are far more accurate which minimizes opportunities for human error andeliminates acceptance of subpar detailing or inadequate construction. This, in turn,results in an increased factor of safety for construction projects Retrofit Methods As previously mentioned, mon retrofit techniques include concrete, FRP, and steeljackets. Concrete jackets are constructed by enlarging the existing cross section with anew layer of concrete and reinforcement (Ersoy et al. 1993). This reinforcement istraditionally provided by hoop or spiral rebar, or welded wire fabric. FRP reinforcementis typically applied two ways: prefabricated jackets or wraps. Both methods have been experimentally researched (Morshed and Kazemi 2020). Steel jackets are constructed byplacing a steel tube with a slightly larger diameter around the member to be area between the existing member and steel tube is typically filled with grout(Priestley et al. 1996). Concrete Jacketing Addition of a concrete jacket is used to enhance flexural strength, ductility, and shearstrength of columns. This technique is more monly used for building columns buthas been applied to some bridge members in Japan. The enhanced confinement isachieved with the use of ties or spirals at a small pitch, or transverse reinforcementspacing (Priestley et al. 1996). Concrete jackets can be used to retrofit beams as well ascolumns (Cheong and MacAlevey 2020). Additional materials can be used to reinforce the retrofit, as long as confinement is enhanced. Rebar Reinforcement Concrete jacketed columns with hoop and spiral reinforcement effectively enhance thestructural capacity of retrofitted members. Ersoy et al. (1993) ran two series of tests tostudy the behavior of strengthened and repaired concrete jacketed columns. The firstseries pares the behavior of jacketed columns with a monolithic reference specimenunder monotonic axial loading. All the concrete for the monolithic specimen was castwith the base column and retrofit reinforcement in place, to provide a specimen withperfect interaction and bond between the base column and retrofit material. Hoopreinforcement is used in the base column and retrofit reinforcement, as shown in Figure . The jackets are applied under two conditions: after the pression loading wasapplied and removed, as well as while the axial load is still applied. It is determined thatcolumns jacketed after unloading performed well, reaching 80 to 90 percent of thestrength of the monolithic reference specimen. Repair jackets applied while the columnis still under load did not perform as well and only reached 50 percent of the axial loadcarried by the monolithic specimen. The second series of tests study the effectiveness ofconcrete jackets with columns tested under bined axial load and bending. Both repairand strengthened jackets behave adequately under monotonic and reversed cyclic loading. Steel Jacketing Steel jackets prevent concrete from expanding laterally as a result of high axial pression strains.