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This study presents critical buckling load optimization of the axially graded layered uniform columns. In the first place, characteristic equations for the critical buckling loads for all boundary conditions are obtained using the transfer matrix method. Then, for each case, square of this equation is taken as a fitness function together with constraints. Due to explicitly unavailable objective function for the critical buckling loads as a function of segment length and volume fraction of the materials, especially for the column structures with higher segment numbers, initially, prescribed value is assumed for it and then the design variables satisfying constraints are searched using Differential Evolution (DE) optimization method coupled with eigen-value routine. For constraint handling, Exterior Penalty Function formulation is adapted to the optimization cycle. Different boundary conditions are considered. The results reveal that maximum increments in the critical buckling loads are attained about 20% for cantilevered and pinned-pinned end conditions and 18% for clamped-clamped case. Finally, the strongest column structure configurations will be determined. The scientific and statistical results confirmed efficiency, reliability and robustness of the Differential Evolution optimization method and it can be used in the similar problems which especially include transcendental functions. Copyright © 2015 Techno-Press, Ltd.

In this study, thermal effects on the free vibration characteristics of composite beams are studied for different temperatures and boundary conditions by using numerical and experimental techniques. Different ply angles, stacking sequences and specimen thickness are also considered. The comparison revealed a good agreement between numerical and experimental results. It is also concluded that regardless of the type of boundary condition and thickness, natural frequencies are decreased with increasing temperature. In addition, a minimum natural frequency value occurs in the natural frequency-ply angle graph at 60° ply angle for all considered temperatures. It can also be stated that the natural frequencies of the composite beams can be adjusted by controlling the temperature as well as the stacking sequences.

Despite the availability of other transport methods such as land and air, marine transportation is the most preferred and widely used transportation method in the world because of its economical advantages. Due to the economical advantages, ship based studies have gained importance especially in recent years. In order to design safe, ergonomic and at the same time economic ships or vessels, both numerical and experimental methods have to be taken into account. Large-scale structural modeling like the cases in ships, on the other hand, typically relies on Finite Element Analysis (FEA) techniques. With the widespread use of Finite Element Methods (FEM) in the field of Computer Aided Design (CAD) engineering, it is possible to increase the strength of a mercantile vessel shipboard. As a consequence, in this study, the strength of a mercantile vessel shipboard has been investigated under working conditions by using ANSYS package program. The results of this study can provide the designer with some guidelines in designing shipboard of mercantile vessels.