Low-Carbon Multimodal Transportation Path Optimization under Dual Uncertainty of Demand and Time

The research on the optimization of a low-carbon multimodal transportation path under uncertainty can have an important theoretical and practical significance in the high-quality development situation. This paper investigates the low-carbon path optimization problem under dual uncertainty. A hybrid robust stochastic optimization (HRSO) model is established considering the transportation cost, time cost and carbon emission cost. In order to solve this problem, a catastrophic adaptive genetic algorithm (CA-GA) based on Monte Carlo sampling is designed and tested for validity. The multimodal transportation schemes and costs under different modes are compared, and the impacts of uncertain parameters are analyzed by a 15-node multimodal transportation network numerical example. The results show that: (1) the uncertain mode will affect the decision-making of multimodal transportation, including the route and mode; (2) robust optimization with uncertain demand will increase the total cost of low-carbon multimodal transportation due to the pursuit of stability; (3) the influence of time uncertainty on the total cost is significant and fuzzy, showing the trend of an irregular wave-shaped change, like the ups and downs of the mountains. The model and algorithm we proposed can provide a theoretical basis for the administrative department and logistic services providers to optimize the transportation scheme under uncertainty.

Punch-Through Risk of Jack-Up Under the Dual Uncertainty of Structure and Foundation

The preload operation of Jack-up in complex multi-layered foundation requires an enhanced understanding of its behavior in punch-through accident and suitable safety analysis tools for the assessment of their reliability in a particular site. In order to evaluate punch-through risk, a risk-consistent method is proposed based on the model of foundation hazard and structural vulnerability. Besides, foundation bearing capacity is evaluated to quantify foundation hazard. Third, to improve the solution efficiency, higher-order moment method (HOMM)-Pushover method has been developed for assessing the structural vulnerability. In addition, case studies are presented to demonstrate the advantages of these techniques and important trends are highlighted by the results of parametric sensitivity studies. More specifically, failure probability analysis has been undertaken using improved method and the punch-through risk is evaluated quantitatively in different hazard levels. The results show that the dual uncertainty of both structure and foundation is crucial for assessment of foundation hazard and structural vulnerability. The randomness of foundation parameters is the dominant factor affecting the punch-through risk, and the risk increases with the increase of preload weight. The time-varying risk in the process of preload operation can be revealed using the risk analysis method mentioned in this paper.