Vibration reduction for a high-speed railway bridge in South Korea

The Gyeongbu high-speed railway (KTX) in Korea has been open to the public since 2004. Since one third of the railway is lying on bridges, a two-span continuous pre-stressed concrete one-cell box girder with 40 m span length was chosen as typical bridge. However, field measurement showed that the chosen bridge type does not satisfy the required design acceleration response of 0.35g under certain circumstances owing to various factors such as rail irregularity, impact owing to discontinuous ballast–sleeper contact, train condition including wheel and interaction between bridge and moving train. This paper intends to find out a measure to control the vibration by changing the structural properties of the originally chosen bridge type. First, a damper system was proposed. Numerical analysis showed that a damper at mid-span could reduce the response by 20 per cent. Accordingly, various types of dampers were installed and compared, but this solution was discarded owing to maintenance cost. Second, added mass solution was proposed. Numerical analysis and scaled-down model indicated that the additional mass could reduce the response by 20 to 40 per cent. Consequently, sand bags of 31.2 tons were dumped at the centre of each span and enabled the vertical acceleration response of the bridge to be successfully controlled in compliance with the design requirements.