Inkyu Rhee, Lee-Hyeon Kim, Hyun-Min Kim and Joo-Beom Lee
International Journal of Railway, vol. 3, no. 3, pp.83-89, 2010

Abstract : This paper attempts to extract the fundamental dynamic properties, i.e. natural frequencies, damping ratios of the 48 mlong, 20o skewed real bridge with PSC girders wrapped by a steel plate. The forced vibration test is achieved by mounting 12 Hz-capacity of artificial oscillator on the top of bridge deck. The acceleration histories at the 9 different locations of deck surface are recorded using accelerometors. From this full-scaled vibration test, the two possible resonance frequencies are detected at 2.38 Hz and 9.86 Hz of the skewed bridge deck by sweeping a beating frequency up to 12 Hz. The absolute acceleration/energy exhibits much higher in case of higher-order twist mode, 9.86 Hz due to the skewness of bridge deck which leads asymmetric situation of vibration. This implies the test bridge is under swinging vertically in fundamental flexure mode while the bridge is also flickered up and down laterally at 9.86 Hz. This is probably by asymmetric geometry of skewed deck. A detailed 3D beam-shell bridge models using finite elements are performed under a series of train loads for modal dynamic analyses. Thereby, the effect of skewness is examined to clarify the lateral flickering caused by asymmetrical geometry of bridge deck.

Keyword : PSC girder wrapped by steel plate (PCS), Skewed bridge, Forced vibration test, Modal dynamic analysis