21世纪钢桥毕业论文外文翻译.docx

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1、英文原文Steel Bridges for the 21st CenturyJohn M. Kulicki, Ph.D., P. E.,Modjeski and Masters, Inc.A collaborative effort of the Federal Highway Administration (FHWA), the United States Navy, and the American Iron and Steel Institute (AISI) has resulted in the development of new steel with great potentia

2、l for use in highway bridge construction. Enhanced performance steel, also known as high-performance steel (HPS), may be defined as any steel with some properties improved over existing ASTM A709, Grades 345W, 485W or 690W, such as:Originally, at least 485 MPa yield, although other strengths up to 9

3、85 MPa are under consideration. There has also been some discussion regarding the desirability of a lower strength HPS, e.g., HPS 345W. Bridge steels with yield strengths of 345, 485 and 690 MPa have been available for decades so it is clear that strength alone does not make a “high performance” ste

4、el;Improved toughness for practical bridge environments, usually expressed as meeting “Zone 3 requirements, i.e., 47 Joules at -23C;Increased weldability, often described in terms of reduced preheat and interpass temperature requirements;No detrimental changes to other important properties;Weatherin

5、g properties at least equal to the older Grade 485W.Stated more simply, HPS has improvements in one or more of the following properties:strength, weldability, ductility, corrosion resistance, fatigue resistance, fracture toughness, fabricability, or formability. The HPS currently available has a yie

6、ld strength of 485 MPaand is produced through improvements in both chemistry and control of the cooling process.The FHWA recognized that research was necessary to consider structural forms which could capitalize on the improvements and properties anticipated as the new HPS was being developed, and t

7、o identify design and specification issues which would have to be addressed to utilize the new material. While the current material has a yield point of 485 MPa, consideration was given to steels with yield points as high as 985 MPa. If strengths of this level are developed in the future, new innova

8、tive structural systems would be needed to utilize the full potential of the improved properties of such steels. A report on an FHWA-sponsored research project to evaluate potential new structural forms and to determine their weight-based efficiency has been reported (Kulicki, et al, 1997). Various

9、aspects of the FHWA report have been well presented in the literature and references (Wassef, et al, June 1994, Kulicki, et al, April 3-5, 1995, Kulicki, et al, July 15-18, 1996,Kulicki, et al, October 15-17, 1996, Kulicki, et al, April 1997, and Kulicki, et al, September 1997).This paper will prese

10、nt a sample of innovative structural systems for tomorrows girder-type bridges, namely, systems that will most effectively utilize very high-strength HPS in bridge construction. The concepts to be considered should not necessarily be limited by current fabrication methods or commercial products, but

11、 not completely out of near-term reach.It will be seen that some of the proposed concepts utilize structural systems which are less redundant that currently favored by most owners. This departure from current preferences has been considered acceptable for the reported studies because of the exceptio

12、nal fracture toughness exhibited by heats of 485W HPS produced by the quenching and tempering variation of thermal mechanical processing used to produce most of the HPS in the United States to-date. The material has sufficient toughness so that in a laboratory test, a fatigue crack grew in a flange

13、to the point that the remaining uncracked flange yielded, but did not undergo brittle fracture. This suggests that the design and safety issues embodied in the Fatigue and Fracture Limit State may be partially or totally relieved in the future. Thus the costly fracture-critical method (FCM) designat

14、ion may also become a thing of the past. Significant savings could result from reduced testing requirements, reduced weld prequalification requirements, relief from some weld repair requirements, reduced disruption of work flow and reduction of paperwork. Figure 1 indicates that the CVN test values

15、for the first four heats of HPS 485W still far exceeded the HPS development target value of 47 Joules at -23C.Figure 1. Comparison of Initial Four Heats of HPS 485W Results withPrevious Results from Traditional 485W (Wilson 1999)Built-Up I-Girders with Corrugated WebsCorrugated plates can be used to

16、 replace the flat webs of conventional built-up I-beams. The corrugated plates can be produced by cold-forming long, flat plates. The corrugations can have a trapezoidal or sine-wave cross-section as shown in Figure 2.While the trapezoidal corrugations are expected to be easier to form, the sine-wav

17、e corrugations are expected to have less residual cold-forming stresses. In addition, the elimination of the sharp corners in the sine-wave corrugations is expected to facilitate welding the web to the flanges and to produce welds with better fatigue resistance.Figure 2. I-Girder with Trapezoidal Co

18、rrugated WebsThe corrugated webs are relatively flexible when subjected to forces parallel to the longitudinal axis of the girder and, therefore, do not contribute to the moment resistance of the girders. The required flanges of a girder with a corrugated web are larger than those of a conventional

19、girder with the same depth. However, corrugated webs allow deeper girders that are not susceptible to web stability problems and, thus, result in thinner webs and smaller flanges. The overall weight of the resulting girders is less than conventional plate girders. A method for splicing corrugated we

20、bs will need to be developed. At least one bridge with trapezoidal corrugations was constructed in France.Lap splices with fillet welds along the edges of the two web plates were provided. Thefatigue resistance of such a splice will need to be proven by testing.Built-Up Girders with Tubular, Concret

21、e-Filled FlangesA flat flange of an I-shaped girder can be replaced by a relatively thin circular or rectangular structural tube. Various concepts for this form are shown in Figure 3. High- strength, non-shrink grout can then be used to fill the tube.The weldability of HPS will allow easier welding

22、of a torsionally stiff tubular flange to a relatively flexible web plate and reduce or eliminate fatigue concerns at the connection. The depth of the web of this system is smaller than that of a conventional girder with the same total depth. The shallower web depth allows thinner, still stable, web

23、plates. Tubular flanges can be used in conjunction with both flat and corrugated web plates. In the case of the corrugated webs, a flat or near-flat surface of the tubular flange will be required to facilitate the weld between the web and the tube. This can be achieved by using a rectangular, hexago

24、nal or octagonal tube, or by flattening a circular tube at the side where the weld is applied. Alternatively, it may be possible to stamp corrugations into a plate and leave a flat tab on the top and bottom to facilitate welding.Figure 3. Tubular Flange GirdersIn the case of tension flanges, prestre

25、ssing strands may be placed inside the tube. The construction sequence can be designed to ensure that the grout inside the tube will remain in compression for all load combinations. The apparent compressive strength of the grout inside the tubular flanges will increase due to confinement. Therefore,

26、 higher allowable stresses in the grout may be allowed.Built-Up I-Girders with Double, Sheet Metal WebsPanels consisting of two metal plates with a filling in between have been used in theaerospace industry for many years. Utilizing the same concept in constructing the webs of bridge girders may res

27、ult in material savings. A typical cross-section of a bridge girder with double web plates is shown in Figure 4. Figure 4. I-Girder withSandwich WebTh e thickness of the web plates is expected to be less than what is generally viewed as minimum plate thickness and, therefore, either high corrosion r

28、esistance may be required to fully utilize the strength of the web plates or the use of stainless steel cladding or metallized coating may provide the required degree of corrosion resistance.Providing adequate connection between the two thin web plates is essential to force the two plates and the fi

29、lling to act as one unit and to eliminate the possibility of each plate buckling independently.The connection between the filling and the web plates can be achieved using one of the following techniques:Using a filling that adheres to the web plates;Using adhesives to connect rigid fillings to the p

30、lates; Mechanical connection.The effect of the weld heat on the filling materials and their connection to the web plates needs to be determined. The use of more advanced directed energy welding methods (e.g., laser welding) may reduce such effects. The resulting welds have less porosity and, therefo

31、re, are less susceptible to fatigue damage. In addition, the lower heat input produces lower residual stresses than what is assumed in the current design specifications.Modifying the design specification to account for the lower residual stresses may further enhance the economy of the system.Summary

32、A design concept that utilized a combination of the ideas discussed above was submitted to CERF in 1996. The proposed bridge consists of two separate structures, each carrying two 3600 mm wide traffic lanes and one pedestrian walkway. A 1800 mm wide left shoulder and a 3000 mm wide right shoulder we

33、re provided on each bridge. With a clear width of 12 000 mm between curbs, the preliminary design herein was performed assuming that each bridge may carry three lanes of traffic. An elevation of the structure is shown in Figure 5 and a cross-section is shown in Figure 6.Figure 5. Bridge ElevationPho

34、tograph 6. Proposed Cross-SectionThe bridge was proposed to be supported longitudinally on two 485 MPa yield strength steel girders. Precast, transversely pretensioned full-width panels are used for the deck. The deck panels are to be longitudinally post-tensioned together during construction such t

35、hat in the final stage the deck will be prestressed in both directions. Girder sections are shown in Figure 7Figure 7. Details of Proposed GirderThe steel fabricating industry has developed highly optimized techniques for fabricating girders out of three flat plates, with or without some stiffeners.

36、 The studies reported herein have indicated that a weight savings on the order of 25% is possible with some of the concepts presented. Clearly there is a difference between weight savings and cost savings; “least weight” does not translate into “least cost”. The market acceptance of new concepts is

37、yet to be proven. Furthermore, since some new equipment will almost certainly be necessary to fabricate either the corrugated plate or the types of tubes which may be necessary for larger structures, it is difficult to see how it will be possible to write-off the acquisition of such facilities on a

38、one-off design. To break the circle of self-fulfilling prophesies regarding the economic viability of new systems, it would be desirable if:Some agency, such as the FHWA, could fund the incremental cost, sometimes referred as “delta cost” to have a series of innovative bridges built using one or two

39、 of the new concepts;An agency could designate a group of bridges in one or more bidding contracts to be required to be built using an innovative design system;A design-build package could be put together for a group of bridges, such as all the bridges on a given stretch of highway, assuming the des

40、ign-build entity found the new concepts to be cost-effective.The near-term marketability of the corrugated web concepts has been enhanced by two developments. There is currently a European firm marketing equipment to corrugate steel plate in the United States, and the Japanese have developed welding

41、 equipment that automatically senses and adjusts its position as it welds corrugated plate to a flat flange. Similarly, there seems to be increased industry interest in steel tubes for bridge applications.The innovative concepts have the potential to save a significant quantity of steel. Some of the

42、 structural systems are worthy of marketplace testing now while others may need more research. Several of the concepts could be employed with conventional existing steels and still result in significant savings in structural steel weight.中文翻译21世纪钢桥经过美国联邦公路管理局（FHWA），国家海军，和美国钢铁协会(AISI)的共同努力，提出了一种在公路桥梁

43、建设中具有巨大潜力的新型钢梁。改性钢，也称为高性能钢（HPS），可认为是在某些性能上高于现有的A709,345W,485W或690W的任何一种钢，例如：通常高性能钢的强度至少要求485MPa，然而，有些屈服强度高达985MPa的钢却不属于高性能钢，另外，还有一些关于低强度高性能钢的讨论，例如，345W的高性能钢。屈服强度为345,485和690MPa的桥梁用钢已经应用了数十年，因此，可以很明显看出单一的屈服强度并不是判断高性能钢的标准；提高桥梁实际环境的韧性，通常被表示为达到3区指标，即在-23C时为47焦耳；增加可焊性，用术语经常被描述为减少预热和层间温度要求；对其它重要特性不引起不利变化；

44、耐久性至少相当于旧的485W级钢；再简要声明一下，高性能钢已改善了钢材的一个或多个性能，具体如下：强度、可焊性、延性、耐蚀性、抗疲劳、断裂韧性、制造性能或变形性。高性能钢目前的屈服强度一般为485MPa，并且通过改进的化学和冷却控制过程生产。FHWA认识到，由于高性能钢的发展，对可利用来改善或预测结构性能的结构形式进行研究是有必要的，同时由于新型材料的使用，鉴定其设计和规格的问题也很必要。虽然目前的材料屈服点为485MPa，但对屈服点高达985MPa的钢也进行了一定考虑。如果这个强度水平在未来有所提高，则需要建立革新性的结构系统以充分利用这种改性钢的全部潜能。一份FHWA赞助的评估潜在的新的结

45、构形式并确定基于重量的效率的研究项目报告报告已经发表（Kulicki, et al, 1997）。这份FHWA报告的各方面内容已在文献和参考中被广泛提及。(Wassef, et al, June 1994, Kulicki, et al, April 3-5, 1995, Kulicki, et al, July 15-18, 1996,Kulicki, et al, October 15-17, 1996, Kulicki, et al, April 1997, and Kulicki, et al,September 1997).本文将介绍一种未来梁桥的创新结构体系样本，换句话说，就是在桥

46、梁施工中更有效的这一理念的考虑不应受到目前制备方法或商业生产的限制，但是短期内还没有完全跳出这一框架。可以看出，这一推荐观念采用少沉冗的结构体系，对目前大部分业主来说是实惠的。这种与当前实际偏好相背离的现象被研究报告视为是可接受的，因为经淬火和回火技术以及高温控轧技术（迄今为止，美国大部分高性能钢都是应用这一技术制造的）生产的485W高性能钢展现出了特别的断裂韧性。这种材料拥有足够的韧性，因此在室内实验时，构件一侧翼缘产生疲劳裂纹，直到未产生裂纹的翼缘屈服，但并未发生脆断。这表明，高性能钢的设计和安全问题集中体现在疲劳方面，未来疲劳断裂极限状态需要部分或完全地缓解。因此，昂贵的断裂临界评估方法

47、（FCM）分析将可能会成为过去的事情。通过减少测试条件，减少焊接限制条件，放宽部分焊接修复条件,减少工作流程分割，并且减少书面工作还可以获得更大量的经济节省。如图1所示是485W的高性能钢的CVN实验测试值，485W高性能钢始终远远超过高性能钢发展的目标值，即-23C时47焦耳。图1 HPS485W与传统485W的CVN试验结果比较带波形腹板的组合工字梁波纹板可以用来取代常规组装工字梁的平腹板。波纹板可以用冷淬成型的长平板制作。如图2所示，波纹板有一个梯形或正弦波形截面。虽然梯形波纹板被认为将较容易成形，但正弦波形波纹板冷淬成形的残余应力较小，另外，正弦波形波纹板消除了尖锐的角落，预计将更方便腹板与翼缘板的焊接，同时将生成具有更好疲劳抗力的焊缝。图2 带正弦曲线波折腹板的组合工字梁波形腹板在承受平行于梁纵轴方向的力时相对较柔性，因此不对梁的弯矩抵抗做贡献。带波形腹板的梁需要比同高度的传统钢梁更大的翼板，然而，当梁高较大时带波形腹板的工字梁不易受到腹板屈曲稳定问题的影响，因此可以使用更细的腹板和更小的翼板，从而使带波形腹板组合梁的整体重量小于传统板梁。目前连接波形腹板的方法尚需发展，至少已有一座带梯形波纹腹板的桥梁在法国建成，两腹板边缘角焊缝的结合方法为同类结构提供了参考。这种结合方式的疲劳抵抗性能需要通过试验证明。带圆形钢管混凝土翼缘的组合梁工字梁的一个平面翼缘可以用相对较薄的