[雙語(yǔ)翻譯]--外文翻譯--新舊金山—奧克蘭海灣大橋主跨 懸索循環(huán)錨固體系設(shè)計(jì)（原文）

1、Design of Looping Cable Anchorage System for New San Francisco–Oakland Bay Bridge Main Suspension SpanJohn Sun, P.E.1; Rafael Manzanarez, P.E.2; and Marwan Nader, P.E.3Abstract: Located at the rocky edge of the Yerba Bue

2、na Island, the west anchorage of the San Francisco–Oakland Bay Bridge suspension span serves as the anchor for this single tower self-anchored suspension bridge. With extensive comparative studies on numerous alternative

3、s, the new looping cable anchorage system is recommended for the final design of the west anchorage of the self-anchored suspension span. The looping cable anchorage system essentially consists of a prestressed concrete

4、portal frame, a looping anchorage cable, deviation saddles, a jacking saddle, independent tie-down systems, and gravity reinforced-concrete foundations. This anchorage system is chosen for its structural efficiency and d

5、imensional compactness. This paper describes major design issues, design philosophy, concept development, and key structural elements and details of this innovative suspension cable anchorage system.DOI: 10.1061/?ASCE?10

6、84-0702?2002?7:6?315?CE Database keywords: California; Bridges, suspension; Design; Bridges, cable-stayed.IntroductionIn May of 1998, the Bay Area Metropolitan Transportation Com- mission selected the self-anchored, sing

7、le tower suspension alter- native as the signature span of the San Francisco–Oakland Bay Bridge east span seismic safety project ?T. Y. Lin 2001?. The rendering of the bridge is shown in Fig. 1. While the single tower as

8、ymmetric suspension bridge satisfies the aesthetic preference of the bridge type selection committee, the concept of ‘‘self-anchored’’ is dictated by the geotechnical condition, shown in Fig. 2. At the east anchorage pie

9、r, the com- bined depth of young bay mud, old bay mud, and sand layers reaches more than 100 m above the Franciscan rock formation. Such soil conditions make construction of the conventional earth anchorage undesirable i

10、n both technical and economic terms. The deck anchorage system becomes the natural choice for the east anchorage, and consequently for the west anchorage. The general elevation and plan of the east bay bridge main span a

11、re shown in Figs. 3 and 4. With a 385 m main span and a 180 m side span, the asymmetrical suspension bridge has a main span length to side span length ratio of 4.3, when compared to a conventional symmetrical suspension

12、span. This span’s asymme- try is recommended primarily to accommodate the main span navigation clearance and to highlight the grace of the catenary curve of the main cable. The 70-m-wide deck structural system consists o

13、f twin ortho- tropic box girders transversely connected with cross beams. Theseemingly single tower is, in fact, a four closely spaced steel shaft frame connected by intermittent shear and tension links along the height

14、of the tower. The deck is monolithically connected to west anchorage pier W2, and is supported on sliding bearings for ser- vice load conditions and effectively pinned for safety evaluation earthquake ?SEE? loads at east

15、 pier E2. The architectural require- ment of a gateway effect created by two planes of hangers means that the main cable must be anchored to the outer sides of the box girders at both east and west ends, and converge on

16、the tower top saddle, as shown in Fig. 4. Among all of the key structural components in this suspension structural system, the west anchorage is one of the most critical elements for several considerations.? The west anc

17、horage piers take up to 70% of the total base shear in the critical longitudinal direction under critical seis- mic loads. This requirement results from the limited shear ca- pacities of a very flexible tower and the eas

18、t anchorage pier being founded on a flexible pile foundation system in the bay mud.1Senior Bridge Engineer, T. Y. Lin International, 825 Battery St., San Francisco, CA 94111. 2Vice President, T. Y. Lin, International, 82

19、5 Battery St., San Fran- cisco, CA 94111. 3Associate, T. Y. Lin International, 825 Battery St., San Francisco, CA94111. Note. Discussion open until April 1, 2003. Separate discussions must be submitted for individual pap

20、ers. To extend the closing date by one month, a written request must be filed with the ASCE Managing Editor. The manuscript for this paper was submitted for review and possible publication on June 19, 2001; approved on J

21、anuary 30, 2002. This paper is part of the Journal of Bridge Engineering, Vol. 7, No. 6, November 1, 2002. ©ASCE, ISSN 1084-0702/2002/6-315–324/$8.00?$.50 per page. Fig. 1. Rendering of east bay suspension spanJOURN

22、AL OF BRIDGE ENGINEERING / NOVEMBER/DECEMBER 2002 / 315of the box. The strands of the main cable are anchored to a stiff- ened grillage welded to the interior faces of the box girder flanges. The longitudinal compression

23、 thrust from the east an- chorage will be balanced by the opposite cable force transmitted to the deck through the cable anchorage stiffening grillage at the west pier. It is important that the splayed saddle be position

24、ed in the specified service loading cable plane to avoid excessive out-of- plane bending action on the splay saddle for various service loads. To spread the strands of the main cable to anchor locations, the length of th

25、e splayed strands should be about 35 m behind the splay saddle. This requirement results in the anchorage box sec- tion of 14–18 m in depth, as shown in Fig. 6. In addition to the aesthetic impact due to the size of the

26、an- chorage box, the large shear and bending on the anchorage deck caused by large uplift action and local effects, such as shear lag, are causes of concern.Box-side Splay Anchorage System II The box-side splay anchorage

27、 system I described in the previous section can be further refined by introducing the closely spaced hangers in front of the splay saddle, as shown in Figs. 7 and 8, inplan and elevation, respectively. Tie-down forces ca

28、n be applied to the hangers so that the main cable is deviated to reduce the cable’s approaching angle, and consequently the uplift action to the anchorage deck and depth of the anchorage box. Due to the large cable size

29、 and inclination angle at the west anchorage, up to 24 rope-hanger sets, spaced across about 25 m of cable length, are required to achieve the deviation. This is a clear aesthetic concern. Also, the first few hangers wil

30、l be subjected to excessive forces under seismic loads.Box-side Anchorage with Midair Floating Saddle The concept of a box-side anchorage with midair floating saddle is illustrated in Fig. 9 in plan and in Fig. 10 in ele

31、vation. This anchorage system uses a midair floating saddle to splay the strands of the main cable, then strands are anchored to the side of the continuing steel box girder over the west pier. The uplift ac- tion of the

32、main cable is transferred to the stiffened deck at the west pier, then tied back to rock by prestressing tendons. To keep the lateral splitting action to a reasonable level, the floating saddle must be located at a minim

33、um of 40 m away from the strand anchors. Consequently, a triangle of strands will be formed above the bridge deck, as shown in Fig. 10. This triangle dimension mass is even more visible when an ‘‘enclosing house’’Fig. 5.

34、 Box-side splay anchorage system I—planFig. 6. Box-side splay anchorage system I—elevationFig. 7. Box-side splay anchorage system II—planFig. 8. Box-side splay anchorage system II—elevationFig. 9. Box-side anchorage with