Finite Element Model Updating And Influence Factors Analysis Of Dynamic Characteristics Of Jack Up Drilling Platform

With the intensification of the oil and gas energy crisis and the improvement of the technical level of the marine engineering equipment,especially as the jack up drilling platform gradually marches into the deep water,it will face the worse sea environment conditions.The interaction of wind,wave,flow and other environmental loads will be more complex,and the structure is easy to produce various forms of damage.The bearing capacity of the structure will be reduced,and platform failure,collapse and other accidents will happen in severe cases,resulting in adverse social impact.Therefore,in order to avoid the occurrence of such accidents,how to carry out the damage detection and structural safety evaluation of the offshore platform,and to find the structural damage and the evaluation of the bearing performance in time become a hot topic.Most of the current research focuses on the damage detection method based on the laboratory model,and the influence of the external load factors and the contact boundary conditions between the main components of the platform is rarely considered in the simplification of the finite element model,and the effect of the actual application is not good.The main reason is the dynamic platform structure caused by the influence of these factors.The change of properties is even greater than that caused by structural damage.Therefore,this research takes the jack up drilling platform as the research object.On the basis of establishing the accurate finite element model of the jack up drilling platform,this paper systematically analyzes the factors that can cause the dynamic characteristics of the platform structure,and provides the accurate finite element model basis for the structural damage detection and the structural safety assessment of the platform.The specific research contents are as follows:(1)Aiming at the construction of the target function and the selection of two factors in the updating of the finite element model,the actual testing conditions of the offshore platform are limited,the parameters to be corrected and the handling of the constraints between the hull and the pile legs are the main errors in the model correction,and a kind of resonance frequency and anti resonance frequency is proposed.The finite element model updating method of RBF neural network is verified by simulation and experimental examples.The results show that all the modified parameters are very close to the target value(test value),and the correlation of the frequency response function curves is also good,which can better reflect the real dynamic characteristics of the structure and verify the effectiveness of the method.(2)On the basis of establishing a more accurate numerical model of the jack up drilling platform,the influence factors that can cause the dynamic characteristics of the platform under the working load are quantitatively analyzed on the basis of the laboratory self lifting platform.Through analysis,it is known that when the mass change reaches 30% of platform quality,the influence of platform quality on the first two order frequency of offshore platform should be considered.The hook load has little effect on the first three order frequencies of offshore platforms and is negligible.