Experimental study of the hydrodynamic responses of a bridge tower to waves and wave currents

To understand the hydrodynamic responses of a bridge tower, which consists of a large round-ended caisson foundation and a diamond-type superstructure, a model experiment at a 1:150 scale was conducted in a laboratory flume. The model was designed to be an elastic structure, which would simulate the dynamic properties of a freestanding bridge tower. Regular waves and the combined action of waves and currents were used as loads in the experiment. The horizontal base shear forces of the foundation and the dynamic responses of displacement and acceleration on the superstructure were measured and analyzed. It is found that the wave current-induced base shear force is approximately equal to the sum of the corresponding wave-induced and current-induced base shear forces. The vibrations of the superstructure are irregular and consist of free vibration at a natural frequency and forced vibration at a wave frequency. The vibration responses driven by the wave currents are slightly larger than those driven by the waves alone, indicating that a forward current does not observably amplify the dynamic responses of the bridge tower.