This paper presents a novel scheduling approach for inland waterway transport (IWT) vessels that must pass through multi-chamber locks. A switching max-plus linear (SMPL) model is built to determine, for each vessel, the most appropriate route, the arrival times at relevant waypoints as well as at the destination, the relative order in which it moves through the network with respect to other vessels, its assignment to certain lock chambers together with other vessels, and its position inside each chamber. The SMPL constraints are translated to mixed integer linear programming (MILP) constraints for the optimization problem to be solvable, and objectives minimizing arrival times or arrival time offsets are defined. The proposed approach is tested on a multi-lock waterway, and its performance is compared to the current state of practice using relevant key performance indicators (KPIs), which allows to demonstrate the superior performance of the proposed approach.

Recent research on variable stiffness laminates have shown both numerically and experimentally that further improvement on the buckling performance is possible by incorporating overlaps that result in variable thickness profiles. We present the concept of overlap-stiffened designs that take advantage of the non-linear coupling between the tow steering and the local thickness, allowing embedded regions of higher stiffness into individual plies of a variable-angle tow (VAT) laminate. The proposed method naturally copes with minimum steering radius constraints of different manufacturing processes by connecting transition regions by means of fiber tow arcs, such that the radius of curvature always cope with a desired minimum radius constraint. The present study focuses on two tow-steering processes: automated fiber placement (AFP) and continuous tow shearing (CTS). Each individual ply exploring the overlap-stiffened design is described using 5 design variables, producing a straight stiffener. A first benchmark study compares overlap-stiffened laminates optimized for a maximum volume-normalized buckling performance under bi-axial compression against a reference straight-fiber laminate. In a second benchmark, overlap-stiffened panels were optimized for minimum weight under a design buckling load constraint, and compared against a reference straight-fiber laminate. For both AFP and CTS, is verified that overlap-stiffened VAT panels can achieve at least the double of the volume-normalized buckling performance of an optimized straight-fiber panel. Moreover, the proposed design method can at least achieve the same weight and buckling load carrying capacity of an optimal straight-fiber panel, demonstrating the potential of the proposed design method to include embedded regions of higher thickness.