Based on ADINA

a finite element model for an existing high bridge pier immersed in water is made with potential fluid based element.A concentrated mass is attached to the top of the structure to simply simulate the bridge deck.A systematic study is carried out on the dynamic characteristics and seismic responses for various water depths.A simultaneous work is also done for the model on the basis of the Morison equation neglecting the velocity part and the result is compared with the PB model.Some conclusions are drawn:（1） The structural frequency is smaller in the presence of surrounding water

and this trend grows as water depth increases

meanwhile the corresponding result from the Morison model is more obvious than the PB model.（2） The top acceleration of the pier is more sensitive to water depth than the top displacement

and that also happens to base shear force compared with base moment.（3） Seismic response will reduce when including the effect of concentrated mass attached to the top of the pier.（4） Result of seismic responses for the Morison model is more conservative in contrast with the PB model.