Numerical Analysis on Variation of Dynamic Response of Girder Bridges with Torsional Reinforcement Panels

¹ Korea Institute of Civil Engineering and Building Technology, Structural Engineering Research Institute, Goyang, 411-712 Korea
² BNG Consultants, Sungnam, 463-825 Korea

^a Corresponding author: jykang@kict.re.kr

Abstract

The dynamic flexural behaviour of the railway bridge is influenced by its torsional behaviour. Especially, in the case of girder railway bridges, the dynamic response tends to amplify when the natural frequency in flexure (1^st vibration mode) is close to that in torsion (2^nd vibration mode). In order to prevent such situation, it is necessary to adopt a flexural-to-torsional natural frequency ratio larger than 120%. This study proposes a solution shifting the natural frequency in torsion to high frequency range and restraining torsion by installing concrete panels on the bottom flange of the girder so as to prevent the superposition of the responses in the girder bridge. The applicability of this solution is examined by finite element analysis of the shift of the torsional natural frequency and change in the dynamic response according to the installation of the concrete panels. The analytical results for a 30 m-span girder railway bridge indicate that installing the concrete panels increases the natural frequency in torsion by restraining the torsional behaviour and reduces also the overall dynamic response. It is seen that the installation of 100 mm-thick concrete panels along a section of 4 m at both extremities of the girder can reduce the dynamic response by more than 30%.