碳纤维材料混凝土桥梁中英文对照外文翻译文献Word格式文档下载.docx

1、Structural Rehabilitation of Concrete Bridges with CFRP Composites-Practical Details and ApplicationsABSTRACT: Many old existing bridges are still active in the various highway transportation networks, carrying heavier and faster trucks, in all kinds of environments. Water, salt, and wind have cause

2、d 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） composites. There appear to be very limited guid

3、es 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 of detailing on ductility and behavior o

4、f 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 life of bridges. These factors include

5、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, and may result in structural failure. In

6、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 carry capacity of the bridge.One attempt to

7、 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, Europe and Japan, CFRP has been extensively investigated and applied. Several design guides have been developed for strengthening

8、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 presents guidelines for repair of deteriorated concrete bridges, along with proper detailing. Evaluation, nondestructive testing, and

9、rehabilitation of deteriorated concrete bridges with CFRP composites are presented. Successful application of CFRP composites requires good detailing as the forces developed in the CFRP sheets are transferred by bond at the concrete-CFRP interface. The effect of detailing on ductility and behavior o

10、f CFRP strengthened concrete bridges will also be discussed and presented.2 Deteriorated Concrete BridgesDurability of bridges is of major concern. Increasing number of bridges are experiencing significant amounts of deterioration prior to reaching their design service life. This premature deteriora

11、tion 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 associated with it. In many cases, the root of a deterioration problem is caused by corrosion of steel reinforcement in concrete struc

12、tures. Concrete normally acts to provide a high degree of protection against corrosion of the embedded reinforcement. However, corrosion will result in those cases that typically experience poor concrete quality, inadequate design or construction, and harsh environmental conditions. If not treated a

13、 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 leading to a structural deficiency3 Non-destructive Testing of Deteriorated Concrete Bridge PiersIn order to design a successful retrof

14、it system, the condition of the existing bridge should be thoroughly evaluated. Evaluation of existing bridge elements or systems involves review of the asbuilt drawings, as well as accurate estimate of the condition of the existing bridge, as shown in Figure2. Depending on the purpose of evaluation

15、, non-destructive tests may involve estimation of strength, salt contents, corrosion rates, alkalinity in concrete, etc.Figure2 Visible concrete distress marked on an elevation of a concrete bridge pierAlthough most of the non-destructive tests do not cause any damage to existing bridges, some NDT m

16、ay 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 but fall under non-destructive testing.In order to select the most appropriate non-destructive test for a particular case, the purpose

17、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. The strength methods may include; compressive test （e.g. core test/rebound hammer/ ultrasonic pulse velocity）, surface hardness te

18、st （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-meter）, locating rebars （rebar locator）, rebar size （some rebar locators/rebar data scan）, concrete moisture （acquameter/moisture

19、 meter）, cracking （visual test/impact echo/ultrasonic pulse velocity）, delamination （hammer test/ ultrasonic pulse velocity/impact echo）, flaws and internal cracking （ultrasonic pulse velocity/impact echo）, dynamic modulus of elasticity （ultrasonic pulse velocity）, Possions ratio （ultrasonic pulse v

20、elocity）, thickness of concrete slab or wall （ultrasonic pulse velocity）, CFRP debonding （hammer test/infrared thermographic technique）, and stain on concrete surface （visual inspection）.Quality and durability test methods may include; rebar corrosion rate field test, chloride profile field test, re

21、bar corrosion analysis, rebar resistivity test, alkali-silica reactivity field test, concrete alkalinity test （carbonation field test）, concrete permeability （field test for permeability）.4 Non-destructive Evaluation of Deteriorated Concrete Bridge PiersThe process of evaluating the structural condi

22、tion 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. The evaluation process can be summarized as follows: （1） Planning for the assessment, （2） Preliminary assessment, wh

23、ich involves examination of available documents, site inspection, materials assessment, and preliminary analysis, （3） Preliminary evaluation, this involves: examination phase, and judgmental phase, and finally （4） the cost-impact study.If the information is insufficient to conduct evaluation to a sp

24、ecific required level, then a detailed evaluation may be conducted following similar steps for the above-mentioned preliminary assessment, but in-depth assessment. Successful analytical evaluation of an existing deteriorated concrete bridge should consider the actual condition of the bridge and leve

25、l 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. should be modeled into a detailed analysis. If such detailed analysis is difficult to accomplish within a reaso

26、nable 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 materials is becoming increasingly attractive to extend the service life of existing concrete bridges. The technology

27、 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 existing concrete bridges started in the 1980s, first as a substitute to bonded steel plates, and then as a su

28、bstitute 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 composite with its unique structural properties. The resin matrix supports the fibers, protect them, and transfe

29、r 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, typically epoxy. Carbon fibers have limited ultimate strain, which may limit the deformability of strengthened

30、 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 could be used to increase the flexural and shear strength of bridge girders including pier cap beams, as shown in

31、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/diagonal CFRP anchors to prevent premature delamination of the longitudinal sheets due to localized debonding a

32、t 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 rounded 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. Figure4 shows rehabilitation of structurally deficient concrete bridge pier using CFRP c