INTRODUCTION
The Yong Jong Grand Bridge is located at the west coast of Korea, and was constructed to connect the new international airport at Yong Jong Island, Inchon, and the mainland. The bridge is 4.4 km long and is composed of three different bridge types—a suspension bridge (550 m), a truss bridge (2,250 m), and steel box bridges. The Grand Bridge (Gil and Cho 1998) has double decks; it will carry six highway lanes on the upper deck, and four highway lanes and dual tracks of a railway on the lower deck. The approach truss bridges are double-deck, Warren truss type bridges. The truss bridges are three-span continuous with a length of 125 m for each span. The width of the truss bridge is 36.1 m.
shoe and dead load of the neighboring truss bridges. The selfanchored suspension bridge typically has limited space for the main cable anchorage, which is located at the stiffening truss, so the air spinning method, which can contain more wires per strand than the parallel wire strand method, is employed to erect the main cables.
2Asst. Mgr., Samsung Corp., 531-7, Kyeongseo-dong, Seo-ku, Inchon, Korea, 404-170.
Note. Discussion open until November 1, 2001. To extend the closing date one month, a written request must be filed with the ASCE Manager of Journals. The manuscript for this paper was submitted for review and possible publication on March 10, 2000; revised August 22, 2000. This paper is part of the Journal of Bridge Engineering, Vol. 6, No. 3, May/ June, 2001. ᭧ASCE, ISSN 1084-0702/01/0003-0183–0188/$8.00 ϩ $.50 per page. Paper No. 22205.
In the construction of the typical earth-anchored suspension bridge, the stiffening truss is constructed after the erection of the main cables and hangers (suspenders). On the contrary, the stiffening truss of the self-anchored suspension bridge is erected on pylons and temporary supports before the spinning of the main cables. In the Grand Bridge, the stiffening truss was divided into eight blocks and erectedrane. As the hangers that link the main cables and the stiffening truss are attached, the main cables of the Grand Bridge will be transformed into a three-dimensional shape. After the attachment of the hangers, the temporary supports for the stiffening truss are removed.
The main feature of the Grand Bridge is the three-span continuous self-anchored suspension bridge. The 550 m long suspension bridge, as shown in Fig. 1, has a main span of 300 m and side spans of 125 m. The main cables of the suspension bridge take a spatial, three-dimensional shape; that is, the main cable planes are inclined. In the plan view, the distance between the main cables is changing along the bridge axis. The distance is shortest at the pylon saddles, and is longest at the center of the main span and the anchorage. When compared to traditional suspension bridges with a vertical cable plane, the suspension bridge with spatial cable system (Gimsing 1994) has a strong torsional stiffness but poses a cable erection problem. The typical earth-anchored suspension bridge has massive concrete anchorages, which carry reactions from the main cables to foundations but take quite a lot of time to build. The self-anchored suspension bridge has the main cable anchorage in the stiffening girder of the bridge so that the forces from the main cable are transferred to the bridge itself. The self-anchored suspension bridge has been rarely constructed due to constructional difficulties (Ochsendorf and Billington 1999). Konohana Bridge in Osaka, Japan, pedestrian bridges in Germany, and the recently proposed Oakland Bay Bridge are a few examples of self-anchored suspension bridges in the world. In the suspension bridge of the Grand Bridge, the horizontal component of the cable force is carried by the stiffening truss, and the vertical component is resisted by a link
1Chf. Res., Inchon Airport Expressway Constr. Ofc., Korea Hwy. Corp., 531-7, Kyeongseo-dong, Seo-ku, Inchon, Korea, 404-170. E-mail: h ࿝ gil@
The main cables of the suspension bridge have 14 strands, which are arranged in a hexagonal form at the pylon saddle, as shown in Fig. 2. Each strand is composed of 480 galvanized parallel wires. The diameter and tensile strength of the wires are 5.1 mm and 1,570 N/mm2 (160 kgf/mm2), respectively. The pylon saddles as shown in Fig. 2 have five channels to house strands, and each channel is separated by a spacer (thickness of 12 mm). To accommodate inclined cable planes, saddles as shown in Fig. 3 are placed with an angle of 12.59Њ in the transverse direction.