CⅡ海洋平台动力响应及模态参数辨识

DYNAMIC RESPONSE ANALYSIS OF A CⅡ JACKET TYPE OFFSHORE PLATFORM AND ITS MODAL PARAMETER IDENTIFICATION

根据CⅡ平台的设计资料,应用ANSYS大型有限元软件对平台进行有限元建模,考虑平台服役海域环境条件及平台设计标准,采用JONSWAP谱描述随机波面,应用Morison方程描述作用在平台桩腿上的波浪载荷,评估了平台振动水平,确定y方向为主振方向。应用随机减量技术提取平台特征节点处的自由振动衰减信号,较正确地识别出平台6阶固有频率,同时识别出相应的模态阻尼比系数。

Vibration characteristics of a jacket type offshore platform under irregular loadings and its structural modal prameters identificatioin for the purpose of its dynamic analysis and structural design are investigated.According to the design information of the CⅡ jacket type offshore platform located in Bohai Bay of China,the structure model is set up by means of ANSYS.To study its dynamic behavior subject to random wave loadings,irregular wave elevation is described as JOSNWAP spectrum and hydrodynamic loading acting on platform legs is calculated by the Morison's equation.The result shows that when the northeast-orientation wind is formed in winter due to the cold and warm air convection,the platform vibration in the y direction is acute,and the 6 order modal parameters of the structure are identified by Ibrahim method based on the structural response measurement.