Optimization based comparison between composite I beams and composite trusses

摘要

The paper presents the economical comparison between composite welded I beams and composite trusses, designed from hollow sections. The comparison was made for simply sup ported beams for different spans and different loads. Composite I beams and composite trussi, were designed in accordance with Eurocode 4 for the conditions of both ultimate and se< viceability limit states. The aim of the comparison was to find out the spans and loads, ai which each of the different structures shows its advantages. In order to carry oui a precis-comparison between the two different composite systems, we applied a structural optimization method rather than classical structural analysis. The optimlization was performed by the nonlin ear programming approach. The economic objective function of self-manufacturing costs w,i defined for the optimization. This way, the obtained design solutions of both systems were not only optimal, but the optimization also caused that the design, resistance, stress and deflection (in)equality constraints were activated at the border of the feasible space. Consequently, the conditions of both the ultimate and serviceability limit states were fully exploited and there was no reserve of resistance for each of the two different structures. At this point the comparison between results of composite 1 beams and composite trusses was performed. Some contour diagrams are also shown at the end of the paper, which should enable researchers and engineer to come to a decision about different composite structures in a faster and more efficient way.