Optimization based comparison between composite I beams and composite trusses

• Published in: Journal of constructional steel research Vol. 59; no. 5; pp. 609 - 625
• Main Authors: Kravanja, S., Šilih, S.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.05.2003
• ISSN: 0143-974X; 1873-5983
• DOI: 10.1016/S0143-974X(02)00045-7

The paper presents the economical comparison between composite welded I beams and composite trusses, designed from hollow sections. The comparison was made for simply supported beams for different spans and different loads. Composite I beams and composite trusses were designed in accordance with Eurocode 4 for the conditions of both ultimate and serviceability limit states. The aim of the comparison was to find out the spans and loads, at which each of the different structures shows its advantages. In order to carry out a precise comparison between the two different composite systems, we applied a structural optimization method rather than classical structural analysis. The optimization was performed by the nonlinear programming approach. The economic objective function of self-manufacturing costs was 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 I beams and composite trusses was performed. Some contour diagrams are also shown at the end of the paper, which should enable researchers and engineers to come to a decision about different composite structures in a faster and more efficient way.