Vibration measurement of Tsing Ma Bridge deck units during erection

The Tsing Ma Suspension Bridge in Hong Kong has a main span of 1377m and an overall length of 2160m. During its construction, ambient vibration measurements were carried out to study the dynamic behaviour of the bridge at various construction stages. This paper reports the random vibration measurements of the first few suspeneded deck units. Two measurements were conducted with the first measurement on the first twin-deck-unit module suspended on the main cables and the second on the three partially connected twin-deck-units suspended on the main cables. The identified lowest 15 natural frequencies of the two systems are within the frequency range 0~0.3 Hz and are very closely distributed. The modal frequencies identified and the corresponding analytical results for both systems are in close agreement with the maximum relative difference being less than 10%.