摘要
矩阵传递法是解决梁结构弯曲振动的有效方法。基于经典传递矩阵法,将海洋立管离散成一系列集中质量和弹性梁单元,可建立一种快速计算海洋立管模态参数(固有频率及模态振型)的方法。通过计算发现,当总传递矩阵行列式值为0时,迭代频率即为立管的固有频率,基于此可求立管的模态振型。适当增加立管的离散单元数可使其固有频率值满足精度的要求。对立管轴向变张力和恒张力这两种情况下的模态进行了比较,发现由表观重力和管内外压差引起的轴向变张力对海洋立管的模态响应有一定的影响,立管的模态位移幅值比恒张力情况下的偏低一些。
Transfer matrix method(TMM)is an effective technique to solve the problem of beam bending vibration.By discretizing the riser into a series of lumped mass and beam elements, an approach to extracting modal characteristics(natural frequency and mode shape) has been developed based on the TMM. Natural frequencies can be determined when the determinant of the total transfer matrix is equal to zero. Then mode shape of the riser can be obtained. Accuracy of the calculation can be improved by increasing discrete elements. It is found that the axial tension and displacement amplitude of the riser with variable tension is lower than that of the riser with constant tension.
引文
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