Dynamic Performance Analysis And Multi-goal Optimization Of A 800t Offshore Mast Crane

In traditional lifting equipments mast crane has certain advantages, among which large tonnage offshore mast crane is increasingly demanded in the field of ocean engineering abroad, but in China the independent research and development for which has just begun. In comparison with land-based crane and ship-based crane, marine environment increases lifting operational difficulty for offshore crane, which requires stronger vibration resistance of its structure. However, the method for structural dynamic analysis induced ship motion load needs improving. In this paper, with the 800 t offshore mast crane as subject, dynamic performance under multi operation conditions was analyzed and optimized. The content of this study is as follows:1) According to the structural features of the target crane, force analysis and load calculation were conducted for boom, rotating platform and mast. On the basis of experience calculation method and numerical calculation method for ship motion load, with AQWA the influence of lifting status and lifting directions on ship motion was analysed under the condition of 90 degree environment load direction, and ship motion load for structure analysis was determined.2) Based on finite element nonlinear analysis theory, in Hypermesh MPC nonlinear contact simulation was defined, which set up the finite element assembled model of the crane. Additionally,.cdb model data were transferred to ANSYS for analyzing static strength and stability of the crane under multi operation conditions. It was shown that 56.4?/ 800 t operational condition was the dangerous working condition, and there existed flaw in thickness distribution of boom and mast.3) Based on vibration theory of multi-degree-of-freedom system, the impact of different lifting angles on inherent vibration characteristics was analysed through modal analysis results with ANSYS, the influence of ship motion excitation was studied through harmonious analysis results, and transient response of the crane was calculated by Newman- ? method for analysing the influence of combined load on dynamic characteristics of the crane. It was shown that ship motion excitation resonated with the first order natural frequency of the crane and the vibration of the top of the boom was the strongest at the moment of main hook unloading under 56.4?/ 800 t operational condition, at which the impact strength remained improving.4) Adopting combined optimization technique of Design Explorer and Altair Optistruct, setting the optimization route from every component to overall crane, taking lightweight as the optimization goal, considering the structure mechanical properties and employing iterative algorithm, screening, MOGA method and NLPQL, this study realized multi-objective optimization for boom, rotating platform and the overall crane, analysed the static and dynamic performance of the crane before and after optimization by comparison, proved the effectiveness and rationality of optimization and proposed a design of isolator for the problem of transient vibration of the boom caused by weight reduction.