外文翻譯---試驗(yàn)研究鋼筋混凝土柱改造方法(完整版)
【正文】 r 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. The steel jacket is equivalent to continuous hoop reinforcement andcan be used for circular columns or rectangular columns with slight modifications, asshown in Figure . Steel jacketing of rectangular columns is not remended because while shear strength is enhanced, flexural ductility is only provided at thecorners. An elliptical steel jacket with concrete infill should be provided for rectangularmembers to fully confine all the concrete (Priestley et al. 1996). A prehensive twopart study was performed by Priestley et al. (1994 a, b) to determine the enhanced shear strength provided by steel jacket retrofitting. The first partof the research focuses on theoretical considerations and test design. It is determined thatACI design equations are overly conservative and new design equations are presented forcircular or rectangular columns in need of shear enhancement. The second part of theresearch focuses on the actual testing of the columns designed according to the proposedequations. It is concluded that steel jackets significantly increase the shear strength and flexural ductility of shear deficient columns, which is shown in Table . Specimenswith an A are asbuilt columns and an R represents retrofitted columns FRP Jacketing Fiber reinforced polymer (FRP) confinement can be provided using several positematerials including fiberglass, carbon fiber, and Kevlar bonded to the confined concretesurface using epoxy (Priestley et al. 1996). Weight and crosssection of the retrofittedmember are not significantly affected with FRP jackets. FRP jackets are most applicablefor circular columns, as stress concentrations can develop in the FRP wrap around thecorners of square or rectangular crosssections. FRP jackets can be used for rectangularor other shaped members, if shape modification is performed to prevent stress concentrations from developing. Two types of FRP retrofits, wraps and prefabricatedposite jackets, are typically utilized. FRP Wraps FRP wraps have several benefits including high strength, light weight, resistance tocorrosion, low cost, and versatility (Saadatmanesh et al. 1997). FRP wrapping is performed by first cleaning the surface of the member to be retrofitted. Epoxy or resin isthen used to attach the flexible FRP fabric to the surface of the me mber to be fabric can be applied dry, but the preferred method is to soak the fabric in epoxybefore application to allow for better cohesion with the surface of the member to beretrofitted. The fabric is then smoothed out to ensure no air pockets exist and extra epoxyis squeezed out the sides. A new layer of epoxy should be applied between each layer offabric and a final layer of epoxy on the outermost surface of the fabric. The wrap shouldthen be allowed to cure at ambient temperatures Saadatmanesh et al. (1997) applies FRP wraps to repair severely damaged reinforcedconcrete columns. Critically stressed regions near the column footing joint are repairedwith FRP wrap. It is evident from the results that FRP posite wraps effectivelyrestore flexural strength an
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