桥梁设计外文翻译文献Word格式.docx

1、原文：A Bridge For All CenturiesAn extremely long-and record setting-main span was designed for the second bridge to across the Panama Canal in order to meet the owners requirement that no piers be placed in the water.Because no disruption of canal traffic was permitted at any time,the cable-stayed bri

2、dge of cast-in-place cancrete was carefully constructed using the balanced-cantilever method.In 1962 ,the Bridge of Americas（Puente de las America） opened to traffic,serving as the only fixed link across the Panama Canal .The bridge was designed to carry 60,000 vehicles per day on four lanes, but it

3、 has beenoperating above its capacity for many years.Toalleviate bottlenecks on the route that the bridge carries over the canal-the Pan-American Highway（Inter-American Highway）-and promotegrowth on the western side of Panama,the countrys Ministry of Public Works（Ministerio de Obras Publicas,or MOP

4、）decided to build a new highway systerm linking the northern part of Panama City,on the eastern side of the canal, to the town of Arraijan,located on the western side of the canal.The Centennial Bridge named to commemorate 100 years of Panamanian independence-has noe been constructed and, when opend

5、, will carry six lanes of traffic. This cable-stayed bridge of cast-in-place cancrete features a main span of 420m,the longest such span for this type of bridge in the Western Hemisphere. In 200 the MOP invited international bridge design firms to compete for the design of the crossing, requesting a

6、 two-package proposal:one techinical, the other financial. A total of eight proposals were received by December 2000 from established bridge design firms all over the world. After short-listing three firms on the basis of the technical merits of their proposals, the MOP selected T.Y.Lin Internationa

7、l, of San Francisco, to prepare the bridge design and provide field construction support based on the firms financial package.The Centennial Bridge desige process was unique and aggressive,incorporating concepts from the traditional design/build/bid method, the design/build method , and the sa-calle

8、d fast-track design process.To complete the construction on time-that is ,within just 27 months-the design of the bridge was carried out to a level of 30 percent before construction bidding began, in December 2001.The selected contractor-the Wiesbaden,Germany,office of Bilfinger Berger,AG-was brough

9、t on board immediately after being selected by the MOP ,just as would be the case in a fast-track approach. The desige of the bridge was then completed in conjunction with construction , a process that id similan to desige/build.The design selected by the client features two single-mast towers,each

10、supporting two sets of stay cables that align in one vertical plane.Concrete was used to construct both the towers and the box girder deck,as well as the approach structures.The MOP , in conjunction with the Panama Canal Authority,established the following requirements for the bridge design :A 420m,

11、the minimum length for the main span to accommodate the recently widened Gaillard Cut,a narrow portion of the canal crossing the Continental Divide that was straightened and widened to 275m in 2002;A navigational envelope consisting of 80m of vertical clearance and 70m of horizontal clearance to acc

12、ommodate the safe passage of a crane of World War 11 vintage-a gift from the U.S.government that is used by the Panama Canal Authority to maintain the canal gates and facilities;A roadway wide enough to carry six lanes of traffic, three in each direction;A deck able to accommodate a 1.5m wide pedest

13、rian walkway;A design that would adhere to the American Association of State Highway and Transportation Official standard for a 100-year service life and offer HS-25 truck loading;A structure that could carry two 0.6m dianeter water lines;A construction method that would not cross the canal at any t

14、ime or interrupt canal operationa in any way.Because of the bridges long main span and the potential for strong seismic activity in the area,no single building code covered all aspects of the project.Therefore the team from T.Y. Lin International determinded which portions of several standard bridge

15、 specifications were applicable and which were not.The following design codes were used in developing the design criteria for the bridge，it is standard specifications for highway bridge ,16th ed,1996It was paramount that the towers of the cable-stayed structucture be erected on land to avoid potenti

16、al ship collision and the need to construct expensive deep foundation in water. However, geological maps and boring logs produced during the preliminary design phrase revealed that the east and west banks of the canal, where the towers were to be located, featured vastly different geologicaland soil

17、 conditions. On the east side of the canal, beneath shallow layers of overburden that rangs in consistency from soft to hard, lies a block of basalt ranging from medium hard to hard with very closely spaced joint.The engineers determined that the basalt would provide a competent platform for the con

18、struction of shallow foundation for tower, piers, and approach structures on this side of bridge.The west side, however,featured the infamous Cucaracha Formation, which is a heterogeneous conglomerate of clay shale with inclusions of sandstone, basalt,and ash that is prone to landslide. As a sudsurf

19、ace stratum the Cucaracha Formation is quite stable,but it quickly erodes when exposed to the elements. The engineers determined that deep foundations would therefore be needed for the western approach structure,the west tower,and the western piers.Before a detailed design of the foundationa could b

20、e developed,a thorough analysis of the seismic hazards at the site was required,The design seismic load for the project was developed on the basis of a probabilistic seismic hazard assessment that considered the conditions at the site.Such an assessment establishes the return period for a given eart

21、hquake and the corresponding intensity of ground shaking in the horizontal directtion in terms of an acceleration response spectrum.The PSHA determined two dominant seismic sources: a subduction source zone associated with the North Panama Deformed Belt capable of producing a seimic event as strong

22、as 7.7MW,and the Rio Gatun Fault, capable of producing an event as strong as 6.5MW.The 7.7MW NPDB event was used as the safety evluation earthquake,that is,the maximum earthquake that could strike without putting the bridge out of service.The damage to the bridge would be minor but would require som

23、e closures of the bridge.The 6.5MWRio Gatun Fault event was used as the foundational evaluation earthquake,a lower-level temblor that would cause minimal damage to the bridge and would not require closures.For the FEE load case,the SEE loading was scaled back by two-thirds.The FEE is assumed to have

24、 a peak acceleration of 0.21g and a return period of 500 years; the probability that it will be exceeded within 50 years is 10 pencent and within 100 years,18 persent.The SEE is assumed to have a peak acceleration of 1.33g and a return period of 2,500 years;the probability that it will be exceeded w

25、ithin 50 years is 2 pencent and within 100 years,4 persent. Because of uncertainty about the direction from which the seismic waves would approach the site, a single response spectrum-a curve showing the mathematically computed maximum response of a set of simple damped harmonic oscillators of diffe

26、rent natural frequencies to a particular earthquake ground acceleration-was used to characterize mitions in two mutually orthogonal directions in the horizontal plane.To conduct a time-history analysis of the bridges multiple supports,a set of synthetic motions with three components-longitudinal,tra

27、nsverse,and vertical-was developd using an iterative technique.Recorded ground motions from an earthquake in Chile in 1985 were used as “seed”motions for the sythesis process.A time delay estimate-that is,an estimate of the time it would take for the motions generated by the SEEand FEE earthquakes t

28、o travel from one point to the next-was create using the assumed seismic wave velocity and the distance between the piers of the bridge.Using an assumed was velocity of approximately 2.5km/s,a delay on the order of half a second to a second is appropriate for a bridge 1 to 2km long.Soil-foundation i

29、nteraction studies were performed to determine the stiffness of the soil and foundation as well as the seismic excitation measurement that would be used in the dynamic analyses.The studieswere conducted by means of soil-pile models using linear and nonlinear soil layera of varying depths.The equival

30、ent pile lengths in the studies-that is, the lengths representing the portions of a given pile that would actually be affected by a given earthquake-induced ground motion-ranged from2to10m.In such a three-dimensional model,there are six ways in which the soil can resist the movement of the lpile bec

31、ause of its stiffness:throngh axial force in the three directions and through bending moments in three directions.Because the bridge site contains so many layers of varying soil types,each layer had to be represented by a different stiffness matrix and then analyzed.Once the above analyses were comp

32、leted,the T.Y.Lin International engineers-taking into consideration the project requirements developedby the owener-evaluated several different concrete cable-stayed designs.A number of structural systems were investigated,the main variables,superstructure cross sections,and the varying support conditions described above.The requirement that the evevation of the deck be quite high strongly influenced the tower configuration.For the proposed deck elevation of more than 80m,the most economical tower shapes included single-and dual-mast towers as well as “goal post”towers-that is,a d