桥梁毕业设计外文翻译0

1、Structural Rehabilitation of Concrete Bridges with CFRP Composites-Practical Details and ApplicationsRiyad S. ABOUTAHA1, and Nuttawat CHUTARAT2ABSTRACT: Many old existing bridges are still active in the various highway transportation networks, carrying heavier and faster trucks, in all kinds of envi

2、ronments. Water, salt, and wind have caused damage to these old bridges, and scarcity of maintenance funds has aggravated their conditions. One attempt to restore the original condition; and to extend the service life of concrete bridges is by the use of carbon fiber reinforced polymer (CFRP composi

3、tes. There appear to be very limited guides on repair of deteriorated concrete bridges with CFRP composites. In this paper, guidelines for nondestructive evaluation (NDE, nondestructive testing (NDT, and rehabilitation of deteriorated concrete bridges with CFRP composites are presented. The effect o

4、f detailing on ductility and behavior of CFRP strengthened concrete bridges are also discussed and presented.KEYWORDS: Concrete deterioration, corrosion of steel, bridge rehabilitation, CFRP composites.1 IntroductionThere are several destructive external environmental factors that limit the service

5、life of bridges. These factors include but not limited to chemical attacks, corrosion of reinforcing steel bars, carbonation of concrete, and chemical reaction of aggregate. If bridges were not well maintained, these factors may lead to a structural deficiency, which reduces the margin of safety, an

6、d may result in structural failure. In order to rehabilitate and/or strengthen deteriorated existing bridges, thorough evaluation should be conducted. The purpose of the evaluation is to assess the actual condition of any existing bridge, and generally to examine the remaining strength and load carr

7、y capacity of the bridge.1 Associate Professor, Syracuse University, U.S.A.2 Lecturer, Sripatum University, Thailand.One attempt to restore the original condition, and to extend the service life of concrete bridges is by the use of carbon fiber reinforced polymer (CFRP composites. In North America,

8、Europe and Japan, CFRP has been extensively investigated and applied. Several design guides have been developed for strengthening of concrete bridges with CFRP composites. However, there appear to be very limited guides on repair of deteriorated concrete bridges with CFRP composites. This paper pres

9、ents guidelines for repair of deteriorated concrete bridges, along with proper detailing. Evaluation, nondestructive testing, and rehabilitation of deteriorated concrete bridges with CFRP composites are presented. Successful application of CFRP composites requires good detailing as the forces develo

10、ped in the CFRP sheets are transferred by bond at the concrete-CFRP interface. The effect of detailing on ductility and behavior of CFRP strengthened concrete bridges will also be discussed and presented.2 Deteriorated Concrete BridgesDurability of bridges is of major concern. Increasing number of b

11、ridges are experiencing significant amounts of deterioration prior to reaching their design service life. This premature deterioration considered a problem in terms of the structural integrity and safety of the bridge. In addition, deterioration of a bridge has a considerable magnitude of costs asso

12、ciated with it. In many cases, the root of a deterioration problem is caused by corrosion of steel reinforcement in concrete structures. Concrete normally acts to provide a high degree of protection against corrosion of the embedded reinforcement. However, corrosion will result in those cases that t

13、ypically experience poor concrete quality, inadequate design or construction, and harsh environmental conditions. If not treated a durability problem, e.g. corrosion, may turn into a strength problem leading to a structural deficiency, as shown in Figure1.Figure1 Corrosion of the steel bars is leadi

14、ng to a structural deficiency3 Non-destructive Testing of Deteriorated Concrete Bridge PiersIn order to design a successful retrofit system, the condition of the existing bridge should be thoroughly evaluated. Evaluation of existing bridge elements or systems involves review of the asbuilt drawings,

15、 as well as accurate estimate of the condition of the existing bridge, as shown in Figure2. Depending on the purpose of evaluation, non-destructive tests may involve estimation of strength, salt contents, corrosion rates, alkalinity in concrete, etc.Figure2 Visible concrete distress marked on an ele

16、vation of a concrete bridge pierAlthough most of the non-destructive tests do not cause any damage to existing bridges, some NDT may cause minor local damage (e.g. drilled holes & coring that should be repaired right after the NDT. These tests are also referred to as partial destructive tests bu

17、t fall under non-destructive testing.In order to select the most appropriate non-destructive test for a particular case, the purpose of the test should be identified. In general, there are three types of NDT to investigate: (1 strength, (2 other structural properties, and (3 quality and durability.

18、The strength methods may include; compressive test (e.g. core test/rebound hammer/ ultrasonic pulse velocity, surface hardness test (e.g. rebound hammer, penetration test (e.g. Windsor probe, and pullout test (anchor test.Other structural test methods may include; concrete cover thickness (cover-met

19、er, locating rebars (rebar locator, rebar size (some rebar locators/rebar data scan, concrete moisture (acquameter/moisture meter, cracking (visual test/impact echo/ultrasonic pulse velocity, delamination (hammer test/ ultrasonic pulse velocity/impact echo, flaws and internal cracking (ultrasonic pu

20、lse velocity/impact echo, dynamic modulus of elasticity (ultrasonic pulse velocity, Possions ratio (ultrasonic pulse velocity, thickness of concrete slab or wall (ultrasonic pulse velocity, CFRP debonding (hammer test/infrared thermographic technique, and stain on concrete surface (visual inspection

21、.Quality and durability test methods may include; rebar corrosion rate field test, chloride profile field test, rebar corrosion analysis, rebar resistivity test, alkali-silica reactivity field test, concrete alkalinity test (carbonation field test, concrete permeability (field test for permeability.

22、4 Non-destructive Evaluation of Deteriorated Concrete Bridge PiersThe process of evaluating the structural condition of an existing concrete bridge consists of collecting information, e.g. drawings and construction & inspection records, analyzing NDT data, and structural analysis of the bridge.

23、The evaluation process can be summarized as follows: (1 Planning for the assessment, (2 Preliminary assessment, which involves examination of available documents, site inspection, materials assessment, and preliminary analysis, (3 Preliminary evaluation, this involves: examination phase, and judgmen

24、tal phase, and finally (4 the cost-impact study.If the information is insufficient to conduct evaluation to a specific required level, then a detailed evaluation may be conducted following similar steps for the above-mentioned preliminary assessment, but in-depth assessment. Successful analytical ev

25、aluation of an existing deteriorated concrete bridge should consider the actual condition of the bridge and level of deterioration of various elements. Factors, e.g. actual concrete strength, level of damage/deterioration, actual size of corroded rebars, loss of bond between steel and concrete, etc.

26、 should be modeled into a detailed analysis. If such detailed analysis is difficult to accomplish within a reasonable period of time, then evaluation by field load testing of the actual bridge in question may be required.5 Bridge Rehabilitation with CFRP CompositesApplication of CFRP composite mater

27、ials is becoming increasingly attractive to extend the service life of existing concrete bridges. The technology of strengthening existing bridges with externally bonded CFRP composites was developed primarily in Japan (FRP sheets, and Europe (laminates. The use of these materials for strengthening

28、existing concrete bridges started in the 1980s, first as a substitute to bonded steel plates, and then as a substitute for steel jackets for seismic retrofit of bridge columns. CFRP Composite materials are composed of fiber reinforcement bonded together with a resin matrix. The fibers provide the co

29、mposite with its unique structural properties. The resin matrix supports the fibers, protect them, and transfer the applied load to the fibers through shearing stresses. Most of the commercially available CFRP systems in the construction market consist of uniaxial fibers embedded in a resin matrix,

30、typically epoxy. Carbon fibers have limited ultimate strain, which may limit the deformability of strengthened members. However, under traffic loads, local debonding between FRP sheets and concrete substrate would allow for acceptable level of global deformations before failure. CFRP composites coul

31、d be used to increase the flexural and shear strength of bridge girders including pier cap beams, as shown in Figure3. In order to increase the ductility of CFRP strengthened concrete girders, the longitudinal CFRP composite sheets used for flexural strengthening should be anchored with transverse/d

32、iagonal CFRP anchors to prevent premature delamination of the longitudinal sheets due to localized debonding at the concrete surface-CFRP sheet interface. In order to prevent stress concentration and premature fracture of the CFRP sheets at the corners of concrete members, the corners should be roun

33、ded at 50mm (2.0 inch radius, as shown in Figure3.Deterioration of concrete bridge members due to corrosion of steel bars usually leads in loss of steel section and delamination of concrete cover. As a result, such deterioration may lead to structural deficiency that requires immediate attention. Fi

34、gure4 shows rehabilitation of structurally deficient concrete bridge pier using CFRP composites.Figure3 Flexural and shear strengthening of concrete bridge pier with FRP compositesFigure4 Rehabilitation of deteriorated concrete bridge pier with CFRP composites6 Summary and ConclusionsEvaluation, non

35、-destructive testing and rehabilitation of deteriorated concrete bridges were presented. Deterioration of concrete bridge components due to corrosion may lead to structural deficiencies, e.g. flexural and/or shear failures. Application of CFRP composite materials is becoming increasingly attractive

36、solution to extend the service life of existing concrete bridges. CFRP composites could be utilized for flexural and shear strengthening, as well as for restoration of deteriorated concrete bridge components. The CFRP composite sheets should be well detailed to prevent stress concentration and prema

37、ture fracture or delamination. For successful rehabilitation of concrete bridges in corrosive environments, a corrosion protection system should be used along with the CFRP system.碳纤维复合材料修复混凝土桥梁结构的详述及应用Riyad S. ABOUTAHA1, and Nuttawat CHUTARAT2摘要：在各式各样的公路交通网络中，许多现有的古老桥梁，在各种恶劣的环境下，如更重的荷载和更快的车辆等条件下，依然

38、在被使用着。冲刷、腐蚀和风化对这些古老的桥梁已经造成了破坏，而维修资金短缺更加剧了它们的损坏。一个利用碳纤维增强复合材料（CFRP）来延长混凝土桥梁的使用寿命的想法使桥梁恢复了原有的状态。然而，采用碳纤维复合材料修复受损混凝土桥梁的指导和规范还非常有限。在本文中对无损探伤、无损检测和利用碳纤维复合材料修复已遭侵蚀的桥梁的方法进行了介绍。此设计对碳纤维增强混凝土桥的延性，及其应用后效果也进行了讨论和介绍。关键词:混凝土腐蚀，钢筋锈蚀，桥梁修复，碳纤维复合材料1 简介在这里存在几个有害的外部环境因素影响着桥梁的耐久性。这些因素包括但又不仅限于化学物的侵蚀，受力钢筋的锈蚀，混凝土的碳化，化学物质的聚

39、合反应。如果桥梁维护不好，这些因素可能导致结构的受损，如结构边缘不稳定或结构损毁。为了修复日渐恶化的现存桥梁，应当对其作彻底的评估。目的是通过大致检测剩余耐久度和承载力，评定出所有现存桥梁的真实情况。应用碳纤维复合材料可以恢复混凝土桥梁最初的状况并延长其使用年限。在北美、欧洲和日本，碳纤维复合材料应经得到深入的研究和广泛的应用。碳纤维复合材料的几个设计指南也已经被应用于强化混凝土桥梁。然而，采用碳纤维复合材料修复损坏的混凝土桥梁的指导和规范还非常有限。本文通过合适的例子给出了修复受损混凝土梁桥的准则，列出了评估、无损检测、碳纤维复合材料复原受损混凝土桥梁。碳纤维复合材料的成功应用由于良好的细节

40、设计，它主要考虑了集中力在碳纤维复合材料中依靠混凝土与碳纤维复合材料接触面间的粘合剂转移。此设计对碳纤维增强混凝土桥的延性和反应的效果也进行了讨论和介绍。2 混凝土桥梁的损坏桥梁的使用年限应该给予极大地关注。越来越多的桥梁在达到设计使用年限之前出现令人侧目的破损。这些过早出现的损坏使得桥梁的结构可靠性和安全性成为1副教授，雪城大学，美国2讲师，斯巴顿大学，泰国了值得考虑的问题。总的来说，桥梁的损坏与考虑它的花费多少是紧密相关的。在很多情况下，损坏问题的根源是混凝土结构中受力钢筋的腐蚀。通常由混凝土保护层预防受力筋的腐蚀。然而，这些具有代表性的问题，如混凝土质量差、不适当的设计或施工和周围恶劣的

41、环境导致了钢筋的腐蚀。如果不及时处理像钢筋腐蚀这种耐久性问题，可能会引起受力不均问题，进而导致结构失稳，如图1所示。图1 钢筋的锈蚀导致的结构失稳3 损坏的混凝土梁桥墩柱的无损检测为了设计一个成功的新式系统，应该对桥梁现有的情况作彻底评估。评价现有桥梁的元素或体系需要翻看asbuilt图纸，才能准确的评估出现有桥梁的状况，如图2所示。根据评估的目的，无损测试应该包括的内容：强度的检测，盐度，腐蚀率，混凝土中碱含量等等。虽然大多数的无损测试对现有桥梁不会造成任何损坏，一些无损检测可能导致的轻微局部损伤（如钻洞取芯），在无损检测完毕后应予以修复。这些测试也被叫作部分破坏性测试,但属于无损检测。图2

42、 混凝土桥墩可见缺陷正面图为了针对特殊情况选择最合适的无损检测，应该明确测试的目的。一般来说,有三种类型的无损检测进行调查：（1）强度；（2）其他结构性质；（3）质量及耐久性。强度测试的方法可能包括：抗压测试（如轴心抗压、反弹测试仪、超声波脉冲速度检测）；表面硬度测试（如反弹仪测试）；贯入度试验（如温莎探针）；拉拔试验（锚索抗拔试验）。其它结构测试方法还包括：混凝土保护层厚度（保护层测量）；定位钢筋位置（钢筋定位器）；钢筋尺寸（某些钢筋定位器、钢筋数据扫描仪）；混凝土的湿度（含水量测试仪、水分测定仪）；混凝土裂缝检查（外观鉴定、回音法、超声波脉冲回波速度检查法）；混凝土分层剥离（锤击试验、超声波脉冲回波速度检查法、回音法）；缺陷和内部开裂（超声波脉冲回波速度检查法、回音法）；动态弹性模量（超声波脉冲回波速度检查法）；泊松比（超声波脉冲回波速度检查法）；混凝土板或墙的厚度（超声波脉冲回波速度检查法）；碳纤