In this research, the optimal design of corrugated bulkheads being used in ship structures is explored by means of the state-of-theart genetic algorithms. The influences of genetic parameters, such as population sizes, crossover probability and mutation probability, on the optimal design of corrugated bulkheads are carefully examined. An objective function defined for the cost of materials and labors is to be minimized to attain the least cost of panel production. The obtained optimal values of each design variable must satisfy the predescribed constraints and some restrictions on fabrication. The optimal values of minimum weight and minimum cost of a panel production are obtained. Finally, a comparison between the method of genetic algorithm and the sequential linear programming optimization algorithm is made to demonstrate the superiority of the proposed genetic algorithms. The numerical simulation results reveal that the genetic algorithms can efficiently minimize panels’ weight and costs in production.

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Optimization of Corrugated Bulkhead Forms By Genetic Algorithm

This paper presents a model for the optimum design of ship transverse frames. An elastic-plastic finite element analysis algorithm for plane frames has been incorporated in the model to evaluate the ultimate strength of the overall frame, and different effects of design loads. Using these strengths and load effects, appropriate design constraints are then formulated to prevent different failure categories; the overall collapse, ultimate limit state failures and serviceability failures. Possible instabilities and effects of combined loads are accounted for in formulating these constraints. Scantlings of the frame structure have been modelled as free design variables. The weight function and different constraint functions are then derived relating design variables in such a way that once parameters for finite element analysis are input, the scheme automatically forms the objective function and all constraints, and then interacts with the simplex algorithm through sequential linearization to find the optimum solution. Thus the scheme is almost automatic. Different layouts of the frame structure have been designed by executing this scheme, which demonstrates the capability of the model and the possibility of weight savings by choosing the appropriate layout. Finally, it is suggested how this model would interact with the design of longitudinal materials to ensure the overall optimality in ship hull module design, to prevent grillage buckling and to validate underlying assumptions in analysis.

Automated optimization of transverse frame layouts for ships by elastic-plastic finite element analysis

An experimental study was made of the behavior of single bay, oneand two-storyed frames, using mild steel models with wide flange sections. A varying horizontal force was applied at the top of a frame model under a constant vertical load on the columns. From the horizontal force-displacement relation. a considerable reduction was observed in the restoring force due to the column loads, indicating the importance of the unstable character due to dead loads on the horizontal restoring force in tall buildings. In general the experimental results show more favourable behavior for a large deformation than the elastic-perfectly plastic theory predicts and a rough estimation of the strainhardening effects accounts for this behavior in a reasonable way.

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An Experimental Study on the Inelastic Behavior of Steel Frames Subjected to Vertical and Horizontal Loading

Experimental and analytical behavior of a hybrid frame, ASCE Vol. 94, ST1, January 1968, Reprint No. 68-1

Composite steel–concrete structures are commonly used in the field of bridges, where the steel frame provides great ease of installation, and concrete provides useful strength at low cost. This construction system makes it possible to seek to use each material to the best of its ability, so as to provide the entire construction system with greater savings. The purpose of this article is to be able to perform the simulation and the non-linear elastic calculation of composite steel–concrete beams through a calculation approach based on a matrix method of displacements. The numerical calculation model developed is based on taking into account the non-linearity of materials, or a set of laws allowing the modeling of the nonlinear behaviors of materials under an instantaneous and monotonous loading increasing until the ruin; the concrete is represented in its post-elastic part by a softening branch in compression and the contribution of the concrete stretched between two successive cracks is taken into account. Steel is represented by a perfect elastoplastic law or an elastoplastic law with firming. The proposed approach has been implemented on the Fortran programming language, where our procedure of numerical modeling of the mechanical behavior seems capable of correctly simulating the three-dimensional nonlinear behavior of isostatic and hyperstatic composite steel–concrete beams, under monotonous (increasing) static loading until ruin. It was validated by comparing the results of our calculations to experimental results or to analytical solutions.

Numerical Procedure for the Three-Dimensional Nonlinear Modelling of Composite Steel–Concrete Beams

Results of full scale tests made to illustrate behavior under load of structures designed by plastic theory; tests were made on beams, small scale frames, and full scale pitched portal frame, all fabricated from standard rolled sections; plastic analysis of moment redistribution, shear, instability and flange buckling effects were checked.

J.W. Dolphin

Papers

Demonstrations of Plastic Behavior of Steel Frames