Mechanical behavior and optimization of multi-objective reliability-based design with simultaneous multiple response for a portal-type drilling derrick on fixed platforms

The non-uniform distributions of stress and strain under typical working conditions and instantaneous variation patterns with different cross-section parameters were obtained for a portal-type drilling derrick by both numerical solutions and simulations. Minimizing the maximum stress, strain and mass were taken as the primary optimization objectives with the beam cross-section parameters as the variables of designing derrick. The mechanical performance of a drilling derrick can be improved by the multi-objective optimization. A decision-making optimization is proposed based on sensitivity analysis of the weighted multi-factor coefficient in weighted extended hesitant fuzzy environments. Then operators are able to optimize the operating systems using the methodologies proposed of multiple-response surface and orthogonal test, and achieve relatively minor structural deformation. The stress increases while the strain reduces with the decreased heights of the legs. It is recommended to enhance the leg strength in a top-to-bottom manner to improve the load-bearing capacity. The maximum stress and strain are located at the bottom of the legs and the beams on the top of the derrick, respectively. The flange thickness on the beam cross-section has the greatest impact on the performance of the derrick. The safety factor is greater than 1.67 and the maximum strain in the derrick is within the allowable value under typical working conditions. The maximum stress, strain and mass of the optimized results decrease from those of the original results by 17.4%, 16.8% and 14.1%, respectively. Multi-objective optimization can therefore provide a theoretical basis and technical reserves for improving the material utilization and selecting derrick structural parameters, which can serve as an effective approach for design and management strategies of portal-type drilling derricks on fixed platforms. • The non-uniform distributions of stress and strain under typical working conditions and instantaneous variation patterns with different cross-section parameters were obtained for a portal-type drilling derrick. • A decision-making optimization is proposed based on sensitivity analysis of the weighted multi-factor coefficient in weighted extended hesitant fuzzy environments. • Operators are able to optimize the operating systems using the methodologies proposed of multiple-response surface and orthogonal test, and achieve relatively minor structural deformation. • The maximum stress and strain are located at the bottom of the legs and the beams. The flange thickness on the beam cross-section has the greatest impact on the performance of the derrick.