Dynamic Response Of Thin Elastic Plate In Wave Field

Due to its widely application,more and more investigation on Very Large Floating Structures(VLFS)has been performed in the recent years.In this study,a thin plate with E=6.4GPa is used to simulate an elastic VLFS.The physical model test is adopted to investigate the dynamic response of the moored elastic plate under both regular and random waves.The effect of relative plate length,relative wave height and water depth was studied,and the results are summarized as:The rectangular plate was moored symmetric,but the upward mooring tension is significantly larger than the leeward mooring tension.Even under regular wave condition,the time history of mooring tension showed significant irregular characters.When the relative plate is small,the variation of mooring tension was dominant by the wave frequency component.However,with larger relative plate,significant low frequency component was observed as well as the wave frequency one.The mooring tension generally increases with the relative wave height,but decreases with the relative plate length.The mooring tension under shallow water depth is larger than that under deep water depth.In spectra of mooring tension,the peak value at the wave frequency decreases with the relative plate length.With B/L<2,the contribution of wave frequency component can be up to 30%;with B/L=3.6 and 5.1,the contribution of wave frequency component decreased to 12% and 5%,respectively;and the wave frequency component was almost disappear with B/L>6.The peak value of low frequency component has insignificant changes with lengthening the relative plate.Under regular wave condition,the surge includes wave and low frequency components.In addition,the low frequency one dominant in the measured range.The effect of wave frequency component became weaker with the increment of the plate.The heave,including both wave and low frequency components,increased with the increment of the wave period.Under irregular wave,the surge,heave and pitch were dominant by the low frequency component.The magnitude of all the above three motions increased with the wave height but decreased with the relative plate length.The comparison of spectral analysis shows that,the low frequency peak of the rigid plate is much larger than that of the elastic plate.But the wave frequency peak of elastic plate is generally larger than that of the rigid plate.It implies that the elasticity of the plate can reduce the low frequency motion component significantly.Wave pressure on the center line of the plate decreased along the wave propagating direction from the head to the rear of the plate.Within the measured ranges,the wave pressure was not monotonous increase or decrease but fluctuated with the relative plate length.The maximum wave pressure on the center line were observed at the relative length of approximately B/L=2-3.