Gyopo Bridge: A Double-Tied Arch Bridge in Poseung-Pyeongtaek Railroad

The Gyopo Bridge is an arch railroad bridge connecting the US military base in Pyeongtaek to the Poseung-Pyeongtaek Railroad. The bridge was designed as a uniquely shaped arch to represent the international cooperation between South Korea and the United States, and also to create visual harmony with Ansung River. The Gyopo Bridge is the longest railroad bridge in South Korea with a new concept, double-tied arch system. The Gyopo Bridge has a single track with a 9,10 m wide deck and a three-span continuous arch with a 130,00 m long main span and 51,20 m long side spans (232,40 m in total). The double-tied arch bridge system is a new structural concept that has strengthened the arch ribs of the previous single-tied arch bridge system using "secondary tension tie". Owing to the secondary tension tie, it is also easy to extend the span length of a double-tied arch bridge by increasing the stiffness of arch ribs. Furthermore, the double-tied arch system can reduce the vibration of the bridge, which will eventually improve the driving safety of traveling trains and prolong the fatigue life of the bridge members.