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191.
A single-degree-of-freedom equation of motion was used for modeling a compliant offshore structure exposed to viscous hydrodynamic loads. The equation of motion contains nonlinearities in the forms of both Duffing stiffness and Morison drag force with current. The water particle velocity and acceleration for calculating the Morison inertia and drag forces are modeled as Gaussian processes based on a Pierson-Moskowitz (P-M) elevation spectrum. The single-degree-of-freedom equation of motion containing different ocean current values are then numerically integrated via a fourth-order Runge-Kutta scheme. Time trajectories of the surge response displacements of the offshore structure and the response probability density curves are obtained. Furthermore, the ocean current influences on the response central moments up to the fourth order are studied. A literature review reveals that this is the first treatment of such a pair of nonlinearities in time domain. The simulation results are analyzed, and some conclusions valuable for engineering design are pointed out. 相似文献
192.
为按时、可靠地将应急物资运达目的地,综合考虑需求和运输环境的双重不确定性、节点疫情感染风险、成本约束、班期限制和转运能力限制等,构建以可靠度最大为目标的应急物资多式联运可靠路径优化模型。同时针对所求问题的NP-难特点,设计蒙特卡洛自适应遗传算法和模拟退火遗传算法进行求解,并引入优劣解距离法对算例的运行结果进行分析。研究结果表明:蒙特卡洛自适应遗传算法较模拟退火遗传算法在求解质量和求解时间方面更优,在交叉概率为0.80,变异概率为0.08,种群大小为50的最佳参数组合下,得到的优化路径最大可靠度为85%,且求解出来的最优路线均未经过存在疫情感染风险的节点,求解结果较好。参数分析表明:在交叉概率相同的条件下,两种算法的平均运行时间均随着变异概率的降低而减少,随着变异概率的增加而增加;多式联运路径优化的决策会受水铁班期的影响。 相似文献
193.
The ultimate strength assessment of platings affected by random corrosion wastage is a key factor for the reliable design of new ships and the structural health monitoring of aged structures, as pitting corrosion wastage significantly affects the ultimate capacity of platings under compression. In this respect, significant efforts have been undertaken in the last decade to assess the ultimate strength drop-off of pitted platings under compression and several interpolating design formulas, based on a large number of FE simulations, have been developed. Nevertheless, current Rules and guidelines don't provide any explicit strength check criterion for pitted platings. Hence, the main aim of current research is the development of a new framework for the ultimate strength assessment of pitted platings, based on a stochastic approach and the endorsement of Monte Carlo simulation. A new formula, which allows evaluating the statistical properties of the plating ultimate strength in presence of random corrosion wastage, is developed. Subsequently, a benchmark study is carried out, to compare the new formula with the existing ones available in literature and a wide set of FE simulations, carried out by Ansys APDL. Current results are discussed, and the effectiveness of the new formula is verified. 相似文献
194.