Structural reliability of two bulk carrier designs

We address the Open Vehicle Routing Problem (OVRP), a variant of the ''classical'' (capacitated and distance constrained) Vehicle Routing Problem (VRP) in which the vehicles are not required to return to the depot after completing their service. We present a heuristic improvement procedure for OVRP based on Integer Linear Programming (ILP) techniques. Given an initial feasible solution to be possibly improved, the method follows a destruct-and-repair paradigm, where the given solution is randomly destroyed (i.e., customers are removed in a random way) and repaired by solving an ILP model, in the attempt of finding a new improved feasible solution. The overall procedure can be considered as a general framework which could be extended to cover other variants of Vehicle Routing Problems. We report computational results on benchmark instances from the literature. In several cases, the proposed algorithm is able to find the new best known solution for the considered instances.

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An ILP Improvement Procedure for the Open Vehicle Routing Problem

Parametric modelling and evolutionary optimization for cost-optimal and low-carbon design of high-rise reinforced concrete buildings

To improve the efficiency of the numerical simulation of the crushing of a honeycomb structure, the equivalent solid model of an aluminium honeycomb core was established. Comparison between the numerical simulation results and experimental evidence revealed that the numerical model of the honeycomb structure was effectively verified as representative. Secondly, the response surfaces for the variation of specific energy absorption (SEA) with side length l and thickness t of the aluminium foil were constructed by surrogate models. Then the relationship between SEA variation and the length l and thickness t of the aluminium foil was investigated. Results indicated that SEA increased with increasing t and decreased with increasing l. The optimum SEA and associated structural parameters (l=1.0 mm, and t=0.16 mm) of an aluminium honeycomb were obtained.

Analysis and optimisation of parameters influencing the out-of-plane energy absorption of an aluminium honeycomb

The investigation of wetdeck slamming phenomenon is a challenging Fluid-Structure Interaction (FSI) problem for both experimental and numerical analysis, requiring detailed design and structural assessment of the physical model. The focus of this paper is to document the design approach and the testing effort devoted to provide a reliable and well identified physical model before the towingtank tests were carried out for giving key insights into the wetdeck load and responses as well as an FSI validation dataset for numerical solvers. Thus, one of the main objectives is reducing the uncertainty linked to the modeling of the multi-hull structure by performing a series of both static and dynamic characterization tests on the as built catamaran model. The insight gained from this test campaign will be used to update the structural models coupled within the FSI solvers to increase the accuracy of the predicted hydrodynamic loading. Among FSI problems still receiving positive attention in ship and offshore engineering, the accurate prediction of complex loading and responses on multi-hull vessels is particularly demanding, since it involves two-way coupling of the deck structure with the flow impinging on it. Currently, there is a gap in available experimental FSI data related to this problem that can be used for numerical solver validation. Current FSI data sets are severely limited by the uncertainties associated with the experimental setups. Furthermore, though segmented model tests have become more feasible and popular for monohulls, not many experimental campaigns (Hermundstad et al. 1995, Kyyro & Hakala 1997, Cheng, F. 1997) exist for segmented catamarans that provide both global and local loads and hull responses. The only systematic investigation on elastically scaled catamarans was carried out by Lavroff et al. (2007, 2013). Dessi et al. (2016) have already illustrated the preliminary experimental results on an elastically scaled model of a SWATH aimed to accurately depict the wave loading and structural response from seakeeping tests. In the present paper the focus is instead on the structural tests performed for the physical model qualification with an extended account of the dry and wet vibration mode identification of the entire catamaran.

Progress in the Analysis and Design of Marine Structures : Proceedings of the 6th International Conference on Marine Structures (MARSTRUCT 2017), May 8-10, 2017, Lisbon, Portugal

http://zbych.zut.edu.pl/fileadmin/WWW/Spis_publikacji/sekulski2009Least-weight_topology_and_size_optimization.pdf

Least-weight topology and size optimization of high speed vehicle-passenger catamaran structure by genetic algorithm

http://zbych.zut.edu.pl/fileadmin/WWW/Spis_publikacji/sekulski2010Multi-objective_topology_and_size_optimization.pdf

Multi-objective topology and size optimization of high-speed vehicle-passenger catamaran structure by genetic algorithm

An evolutionary algorithm for multiobjective optimization of the structural elements of the large spatial sections of ships is presented. The evolutionary algorithm where selection takes place based on the aggregated objective function combined with domination attributes as well as distance to the asymptotic solution is proposed and applied to solve the problem of optimizing structural elements with respect to their weight and surface area on a high-speed vehicle‐passenger catamaran structure with several design variables such as plate thickness, scantlings of longitudinal stiffeners and transverse frames, and spacing between longitudinal and transversal structural members. Details of the computational models were at the level typical for conceptual design. Scantlings were analyzed using the selected rules of a classification society. The results of numerical experiments with the use of the developed algorithm are presented. They show that the proposed genetic algorithm can be a foundation of the effective multiobjective optimization tool for ship structure optimization. Further development of the tool should include more advanced methods for ship structural analysis.

/pdf/ship-hull-structural-multiobjective-optimization-by-2d0w3smh4i.pdf

Ship Hull Structural Multiobjective Optimization by Evolutionary Algorithm

Reduction of hull structural weight is the most important aim in the design of many ship types. But the ability of designers to produce optimal designs of ship structures is severely limited by the calculation techniques available for this task. Complete definition of the optimal structural design requires formulation of size-topology-shape-material optimization task unifying optimization problems from four areas and effective solution of the problem. So far a significant progress towards solution of this problem has not been achieved. In other hand in recent years attempts have been made to apply genetic algorithm (GA) optimization techniques to design of ship structures. An objective of the paper was to create a computer code and investigate a possibility of simultaneous optimization of both topology and scantlings of structural elements of large spacial sections of ships using GA. In the paper GA is applied to solve the problem of structural weight minimisation of a high speed vehicle-passenger catamaran with several design variables as dimensions of the plate thickness, longitudinal stiffeners and transverse frames and spacing between longitudinals and transversal members. Results of numerical experiments obtained using the code are presented. They shows that GA can be an efficient optimization tool for simultaneous design of topology and sizing high speed craft structures.

/pdf/structural-weight-minimization-of-high-speed-vehicle-1rrr3l7aum.pdf

Zbigniew Sekulski

Papers

Least-weight topology and size optimization of high speed vehicle-passenger catamaran structure by genetic algorithm

Multi-objective topology and size optimization of high-speed vehicle-passenger catamaran structure by genetic algorithm

Ship Hull Structural Multiobjective Optimization by Evolutionary Algorithm

Structural weight minimization of high speed vehicle-passenger catamaran by genetic algorithm

3D optimisation problem of the ship hull structure by the genetic algorithm