1、附录 A Bridge to the Future The Chao PhrayaRiverBridge is designed to accommodate marine traffic. The 500 m main span will provid 50.5 m of vertical clearance, and the two towers will be situated away from the main navigation channel. The final component of Thailands new Outer Bangkok Ring Road, the e
2、ight-lane cable-stayed Chao PhrayaRiverBridge, will not only alleviate Bangkoks notoriously heavy traffic but also contribute a new architectural symbol to the capital city. By Ruchu Hsu, RE. The bridge will carry four lanes of traffic in each direction. The upper portion of each tower will have an
3、enclosed chamber for cable anchors, a 1.5 m square opening at the bottom providing easy access for maintenance and inspection. For the past 20 years, Thailands capital, Bangkok, has been constructing expressways to lleviate traffic congestion. Among the major expressway projects in the capital is th
4、e Outer Bangkok Ring Road, a 170 km long highway encircling the city. The road is nearly complete； only the eastern half of the southern leg-the Southern Outer Bangkok Ring Road, or S-OBRR-remains to be constructed. Scheduled for completion in 2007, the 21 km elevated viaduct will incorporate four m
5、ajor interchanges and a cable-stayed bridge over the Chao PhrayaRiver. With a main span of 500 m and two side spans of 220.5 m, the Chao PhrayaRiverBridge will be the longest in Thailand. In 1996 the Department of Highways retained a joint venture team of consultants to design the S-OBRR. The design
6、 team included Asian Engineering Consultants (AEC), Thai Engineering Consultants (TEC), and Siam General Engineering Consultants, all of Bangkok； Oriental Consultants, of Tokyo； and Parsons Brinckerhoff (PB), of New York City. Once the joint venture was formed, designers began a feasibility study of
7、 the Chao PhrayaRiver crossing and set about determining the most suitable type of crossing. Tunnels and cable-stayed bridges were developed and evaluated. Eventually, however, it became clear that a bridge would be more economical, would not interrupt marine traffic, and would best lend itself to t
8、he highway interchange. In 1999 engineers began to design the S-OBRR. The Chao PhrayaRiverBridge design was led by PB and supported by AEC and TEC. Conceptual and preliminary designs were pre-pared by PBS New York staff, and Thai engineers working in Bangkok with the author completed the subsequent
9、final design. The engineers established four design goals. They wanted a bridge that would (1) be long lasting and easily maintained, (2) enhance the city architecturally, (3) be economical and incorporate the maximum amount of local material, and (4) not disrupt marine traffic the Chao PhrayaRiver
10、during construction. Superstructure true that will carry four traffic lanes in each direction and provide 50.5 m of vertical clearance for marine traffic. The bridges two A-shaped towers will straddle the 500 m main span and will stand as stylized representations of the traditional Thai greeting, th
11、e hands steep led together. The superstructure is a steel frame composite with a concrete deck. Stay cables spaced at 12 m intervals along the edge girders are designed to carry the superstructure load. Three anchor piers on each side will provide stability. The bridge features a symmetrical profile
12、 and slopes no more than 3 percent. The bridge was designed for 208 KN loads from trucks-loads 30 percent higher than those set forth by the American Association of State Highway and Transportation Officials in the 16th edition of its Standard Specifications for Highway Bridges (1996). The hollow le
13、gs of the two 187 m high towers are made of reinforced concrete. A horizontal strut just below deck level provides lateral support for the slender legs and reduces deflection. The legs, each supported by two 24 by 24 by 4 m footings, join at the top to form a chamber for cable anchors. Decorative sp
14、heres 3 m in diameter and spires 8 m tall at the top of the towers will be gilded in traditional Thai style. The two towers-one located in shallow water on the east bank, the other behind a wharf on the west bank-will be situated away from the main navigation channel to eliminate the possibility of
15、collisions with the bridge and ensure that marine traffic and wharf operations can proceed unimpeded. The three anchor piers will be situated behind each tower on the bridges back spans. The piers will maximize the vertical and lateral stiffness of the bridge superstructure and the tensional stiffne
16、ss of the main-span superstructure and will stabilize the bridge during strong winds. The A-shaped towers will also contribute to the tensional stiffness of the superstructure. Moment connections between the superstructure and the anchor piers eliminate the need for wind locks, which attach the deck to the
