第七代超深水海洋平台钻机双井架的等强度多目标优化

为了解决第七代超深水海洋平台钻机双井架结构笨重、安全系数小、变形大和材料使用率低等设计不合理的问题，基于等强度理念对双井架进行了优化设计：参照API Spec 2C-2004标准并采用有限元法，分析了双井架在典型工况下不同杆件截面参数时的应力、位移变化规律；以双井架质量、最大应力、最大位移和不同高度段的应力差异程度为优化目标，采用单因素与响应曲面法进行杆件截面参数优化，获得了最优截面参数组合。研究结果表明：①初步设计的双井架在风暴自存工况下安全系数小于API Spec 4F-2013要求的1.67，最大位移大于规范允许值l/400，在井架的下支柱和顶部横杆处最危险；②双井架应力随高度升高而减小，在设计双井架时应偏向从低到高考虑杆件截面强度；③双井架最终优化方案满足各典型工况要求，较之于原方案，质量、最大应力、最大位移和不同高度段应力的最大偏差率分别降低16.18%、29.25%、29.35%、67.67%，提高了材料利用率。结论认为，采用单因素与响应曲面法相结合的等强度多目标截面参数优化方法，对于双井架结构参数优选和相关井架设计具有指导意义。

Equal-strength multi-objective optimization of dual derricks of the seventh-generation ultra-deep water offshore drilling rigs

The dual derrick of the seventh-generation ultra-deep water offshore drilling rigs is structurally bulky with a small safety factor, large deformation and low material utilization ratio. In order to solve these unreasonable design problems, this paper carried out design optimization on the dual derrick based on the concept of equal strength. Firstly, the stress and displacement variation rules of dual derrick at different beam section parameters under typical working conditions were analyzed by referring to API Spec 2C-2004 standard and using finite element method. Then, taking the mass, maximum stress, maximum displacement and stress difference degree at different height segments of dual derrick as optimization objectives, beam section parameters were optimized using single factor and response surface method, and accordingly the optimal section parameter combination was obtained. And the following research results were obtained. First, under the working condition of storm survival, the safety factor of the preliminarily designed dual derrick is lower than the required value in the API Spec 4F-2013 (1.67), the maximum displacement is greater than the allowable value in the specification (l/400), and the lower pillar and the top cross beam are the most dangerous positions. Second, the stress of the dual derrick decreases with the increase of the height, so the sectional strength of the beam shall be considered from bottom to top in the design. Third, the final dual derrick optimization scheme meets the requirements of various typical working conditions, and compared with the original one, its mass, maximum stress, maximum displacement and maximum stress deviation rate at different height segments are reduced by 16.18%, 29.25%, 29.35% and 67.67% respectively and the material utilization ratio is improved. In conclusion, the equal-strength multi-objective section parameter optimization which combines single factor with response surface method is of guiding significance to structural parameter optimization and the related derrick design.