外文翻译---试验研究钢筋混凝土柱改造方法.doc

experimental research of reinforced concrete columnretrofit methodsintroductionas the infrastructure of our country continues to age, the need for effective retrofittreatments has increased. many building and bridge structural components no longerprovide capacity sufficient to meet the required code standards. seismic upgrading andreinforcement protection are two of the major issues requiring retrofits. additionally,many aging structural members no longer provide the load capacity of the original designbecause of concrete cracking, steel corrosion, or other damage. in this research, severalretrofit methods for increasing the axial load capacity of reinforced concrete columnswere tested and analyzed.several currently applied methods for retrofitting columns include concrete jacketing,steel jacketing, and fiber reinforced polymer (frp) jacketing. all three methods havebeen shown to effectively in increase the axial load capacity of columns. in addition, anew reinforcement product, prefabricated cage system (pcs) reinforcement, wasintroduced as a possible reinforcement option for concrete jacket retrofit applications.project scopethree retrofit reinforcement options, concrete jacketing, steel jacketing, and frpwrapping, were experimentally analyzed in the research. three different materialsprovided reinforcement for the concrete jackets: a rebar cage with spiral transversereinforcement, welded wire fabric (wwf), and the aforementioned pcs. all specimenswere tested under axial compression loading only. applied load and displacement weremeasured for all specimens throughout testing until failure. additionally, response of theloaded specimens was observed and documented throughout the testing. behavior of thenewly introduced pcs reinforcement was compared with traditionally used retrofitapplications already currently utilized in the structural engineering industry. advantagesand disadvantages of each retrofit measure were identified. additionally, model conceptswere presented for the response of concrete jacket retrofitted columns based on the workof mander et al. (1988) and cai (1987).project summaryseventeen circular columns were constructed and tested to failure in compression. first,similar reinforced concrete base columns were constructed with spiral transversereinforcement. all base specimens had the same dimensions, transverse, and longitudinaleinforcement. the base specimens were then retrofitted with the different retrofitmethods previously discussed. one specimen, referred to as the base specimen, wastested without any retrofit applied. three specimens were retrofitted with a spiral rebarreinforced concrete jacket. two specimens were reinforced with a welded wire fabricreinforced 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 loaded.this 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 cross-section loaded.retrofit of existing structuresmany structures have historically been constructed using reinforced concrete. typicalordinary concrete consists of four constituents: gravel, sand, water, and cement.reinforced concrete has some type of reinforcement, typically steel, combined withconcrete to produce a stronger system than plain concrete. concrete is strong incompression but weak in tension. tensile forces cause concrete to crack and eventuallyfail in a brittle manner at stresses significantly lower than the compression strength ofconcrete. steel, or another type of reinforcement material, can be used to compensate 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 members.members displaying these adverse affects may be rehabilitated using an appropriateretrofit method.retrofitting is typically done for two reasons: rehabilitation or strengthening. aspreviously discussed, rehabilitation is fixing the structural deficiencies of a damagedstructure or structural member. this may be necessary for aging members that no longerdisplay the strength of the original design. strengthening increases the load-carryingcapacity 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 columns.several 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 benefitspcs reinforcement has some unique properties. the longitudinal and lateralreinforcement for pcs are located the same distance from the center of the membercross-section. this provides increased flexural capacity, using the same amount of steelas a traditional rebar system, and results in more efficient use of the reinforcing steel.the 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 2.4.thickness of the pcs steel determines the dimensions of the reinforcement confining the concrete.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 materials.additionally, pcs reinforcement can be fabricated off-site and immediately placed for concrete casting without additional fieldwork, such as tying, cutting, or bending ofreinforcement, which prolong construction time. off-site 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 sub-par detailing or inadequate construction. this, in turn,results in an increased factor of safety for construction projectsretrofit methodsas previously mentioned, common 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 2005). steel jackets are constructed byplacing a steel tube with a slightly larger diameter around the member to be retrofitted.the area between the existing member and steel tube is typically filled with grout(priestley et al. 1996).concrete jacketingaddition of a concrete jacket is used to enhance flexural strength, ductility, and shearstrength of columns. this technique is more commonly 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 2000). additional materials can be used to reinforce the retrofit, as long as confinement is enhanced.rebar reinforcementconcrete 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 compares 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 2.5. the jackets are applied under two conditions: after the compression 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 combined axial load and bending. both repairand strengthened jackets behave adequately under monotonic and reversed cyclic loading.steel jacketingsteel jackets prevent concrete from expanding laterally as a result of high axialcompression 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 2.10. steel jacketing of rectangular columns is not recommendedbecause 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 comprehensive two-part study was performed by priestley et al. (1994 a, b) todetermine 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 2.1. specimenswith an a are as-built columns and an r represents retrofitted columnsfrp jacketingfiber reinforced polymer (frp) confinement can be provided using several compositematerials including fiberglass, carbon fiber, and kevlar bonded to the confined concretesurface using epoxy (priestley et al. 1996). weight and cross-section 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 cross-sections. 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 prefabricatedcomposite jackets, are typically utilized.frp wrapsfrp wraps have several benefits including high strength, light weight, resistance tocorrosion, low cost, and versatility (saadatmanesh et al. 1997). frp wrapping isperformed 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 member to be retrofitted.the 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 temperaturessaadatmanesh 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 composite wraps effectivelyrestore flexural strength and ductility in damaged columns. similarly, gergely et al.(1998) uses carbon frp wrap to test the performance enhancement of reinforced concretecap beams and cap beam-column joints. the research shows that frp wraps cansignificantly increase the shear capacity and ductility of cap beams and cap beam-columnjoints. hadi (2003) performs similar tests on concrete beams and concludes that frp wraps contribute to the load carrying capacity, as well as flexural strength, of reinforcedconcrete beams. additional layers of frp result in increased flexural strength.xiao and wu (2003b) perform a comprehensive research program to study the behaviorof concrete confined by various types of frp wraps. carbon fiber as well as e-glasswraps are investigated. the methods of application vary between in situ (hand layup)and machine-wound application. again, it is determined that frp composite jacketssignificantly increase the strength and ductility of concrete试验研究钢筋混凝土柱改造方法简介：随着我国基础设施不断老化，因此需要进行改造的设施不断增加。许多建筑物和桥梁的结构组件不再能够提供足够的强度来满足要求。升级加固是应对这一重大问题的方法之一。此外，由于混凝土开裂，钢筋锈蚀，或其他损害，使许多公共设施不再提供原设计要求的承载能力。在本研究中，对怎样提高钢筋混凝土柱轴向负载能力进行了测试和分析。目前应对方法包括混凝土柱加装护套，钢套管，增强纤维复合材料（frp）的护套。以上三种方法已被证明能有效地提高混凝土柱轴向负载能力。此外，新技术pcs加固，有可能成为加固混凝土柱的改造方法。项目范围：三种加固改造方案具体包括护套、钢套管、及玻璃钢包装。三种不同方案提供给混凝土一定的承载力：一个螺旋横向钢筋混凝、wwf和上述构件。所有标本轴向载荷下进行了测试压缩，应用负载和整个位移测量，直到故障检测达到标准为止。此外，并对整个测试进行了观察和记录。新推出的加固技术与目前使用在结构工程领域的应用程序传统技术进行了比较。并对其优势、劣势进行了一一鉴定。此外，此项目还分别给出了对混凝土柱改造方法基础学的作者：mander et al.（1988年）和蔡（1987）。项目主要内容：十七圆柱的构建和测试以失败而告终。首先，钢筋混凝土构建螺旋柱的基础设施都有相同的尺寸。基于此标准，然后应用上前面讨论过的不同改造方法。此标准，简称为基标，测试时被任何改造所应用。对三个标本进行改造与螺旋钢筋钢筋混凝土外套（用钢筋焊接线织物钢筋混凝土外套）。三标本进行改造包装，两个玻璃钢更多的标本进行改造。此外，六名标本用件加固钢筋混凝土外套，包括两种不同厚度构件。九标本有基列的整个横截面和改造面积进行加载。 九标本有基列的整个横截面和改造面积加载，这模拟了改造载荷时的条件是在整个分布式截面。标本有五只基受压柱截面，它模拟了当负载为只适用于原始状态下的条件。每间隔一段时间，其他三标本增加了类似的横向箍筋间距钢筋强度。这些标本也有整个基础柱截面改造。改造现有结构: 历史上有很多结构是由钢筋混凝土建成。典型普通混凝土包括四个成分：砾石、沙子、水和水泥。一般情况下，钢筋混凝土加固具有一定的规范，结合混凝土产生承载力比普通混凝土更好。混凝土柱部分地方的压缩，会使其承载力降低。拉力会导致混凝土产生裂缝，并导致最终失败。钢、钢筋或其他种类的材料，可用于弥补弱强度混凝土，这一系统被称为钢筋混凝土。随着钢筋混凝土的老化，有可能出现许多的不利影响。这些影响包括剥落、剥落、或导致混凝土开裂、腐蚀和随后的强度降低。这些事件可以明显影响结构构件的强度。使用适当的修复改造的方法会降低这些不利影响。两种典型的做法：修复、加强。如前所述，可以修复已损坏的结构、性缺陷结构或结构构件。这可能会使老化的混凝土柱不再显示原设计强度。加强提高了承载能力结构的成员（ersoy et al.1993年）。如果支持负载通过改变结构构件的生活，或者目前的设计标准更严格的要求增援，这可能是非常必要的。此外，结构在地震区域的成员可能需要升级到当前的抗震要求。改造可以适用于任何结构构件，包括梁，柱。传统上使用的几种方法的改造包括混凝土套管、钢套管，以及玻璃钢加强（wipf et al. 1997年）。加固具体的方法可以由钢筋加固或电焊布（wwf）的。此外，一个相对较先进的产品，预制钢筋笼系统（pcs）的，建议作为具体措施来进行具体的操作。pcs优点：构件加固有一些独特的性质。纵向和横向用于pcs加固位于从会员中心相同距离横截面。这可以增加抗弯能力，作为一个传统的钢筋体系，使用相同数量的钢材，并在更多的钢筋有效使用效果。个人电脑的整体行动，消除了纵向和横向分离钢筋。此外，药盒加强是分布在一个平面配置提供更大的约束比钢筋加固。在pcs钢材厚度决定了加固围的尺寸混凝土的强度。构件加固提供了几个额外的好处。钢筋的尺寸是由设计师产生任何所需的要求钢筋。这允许在一个很大的灵活性和效率设计过程中，增强混凝土类型的选择并不限于现有库存材料。此外，混凝土柱加固在制备场完成，立即放置混凝土浇注，无需额外实地考察，如捆绑，切割或弯曲加固，那样会延长施工时间。其外还提供了一个现场制作增加了对钢筋的质量控制水平。在pcs生产，尺寸和间距准确高会最大限度地减少人为错误的机会和消除了低于标准杆详细或不充分的施工验收。这反过来说，这样会使一个建设项目的安全系数增加。改制方法：如前所述，共同改造技术，包括混凝土，玻璃钢，钢夹克。混凝土构造夹克通过扩大与现有的横截面新层混凝土和钢筋（(ersoy et al.。1993年）。这样加强了传统上所提供的钢筋箍或螺旋，或电焊面料。玻璃钢加固通常采用两种方法：预制夹克或包装。这两种方法已被实验研究（morshed and kazemi 2005年）。钢构造夹克与周围放置构件直径略大钢管，然后被改造。现有构件之间的面积和钢管通常是充满了泥浆（priestley et al.1996年）。混凝土养护：加一个具体夹克用来增强弯曲强度，延展性和剪切强度列。这种技术是更普遍用于建筑系列，但已被应用到一些在日本桥体中。增强的混凝土柱实现了与在一个小摊位使用关系或螺旋，或横向加固间距（priestley et al.1996年）。混凝土外套可用于改造以及梁列（cheong and macalevey2000年）。补充材料，可用于加强