基于静动力分析的海洋井架钢结构有限元模型修正方法

Finite element model updating method of offshore derrick steel structures based on dynamic and static analysis

为了得到能够更加真实地反映海洋井架静动态力学性能的有限元模型,本文提出联合运用静动力目标函数的井架结构有限元模型修正方法,相对于单独运用静力、动力目标函数的模型修正方法,本文方法能更好地适应海洋井架的静动态力学特性。为验证该修正理论的正确性,以某海洋井架为原型建立缩尺比为1:14的模型井架。在对该井架进行静动力测试和有限元仿真分析的基础上,根据对结构静动态性能的具体要求提出目标函数与约束条件,通过灵敏度分析选取合适的设计参数,采用一阶搜索优化算法对待修正的设计参数进行优化,得出有限元模型的修正结果。结果表明:与模型修正前相比,修正后井架一阶模态频率的误差减小到了-5.282%,二阶模态频率的误差减小到了-6.320%,而各个测点的应力误差控制在4%以内。这说明该方法可以较好的修正初始有限元模型,使井架有限元模型更加接近真实模型,可进一步用于分析预测井架结构的承载能力和使用寿命。

In order to obtain more truly finite element model to reflect the dynamic and static mechanicalproperties of offshore derricks, a finite element model updating method of derrick structures is proposed combined with dynamic and static objective functions. Compared with the single use of static or dynamic objective function in model updating, it can better response the dynamic and static mechanical properties of the offshore derricks. To verify the correctness of the updating method, a sample model with the simulated ration of 1:14 is built, corresponding dynamic and static testing and finite element simulation analysis are carried out. According to the specific requirements of the dynamic and static properties of the structure, the objective functions and constrained conditions are presented. The appropriate design parameters are selected by the sensitivity analysis and these parameters are optimized by using the first-order search optimization algorithm. The updating results of finite element model show that: compare with the original model results, error of first-order modal frequency of derrick is reduced to-5.282%, error of second-order modal frequency is reduced to-6.320%, while the stress error of each measuring point is controlled in less than 4%. Results obtained indicate that the developed method can update the finite element model to made derrick finite element model approach to the realistic model well. The updating finite element model is reliable, which may be applied for further analysis and prediction of carrying capacity and service life of the derrick.