Weight and cost optimization of welded high strength steel beams

• Weight and cost optimization problems of HSS beams under Eurocode 3 are formulated.
• Both homogeneous and hybrid cross-sections are considered.
• High strength steel provides up to 34% savings in weight compared with S355.
• Hybrid cross-sections reduce the total cost up to 10%.

In this study, economical use of high strength steel in welded beams is considered. The purpose is to compare the performance of high strength steels of grades S500 and S700 with the reference grade S355, when employed in simply supported, geometrically double-symmetric I-beams under uniform transverse loading. The beams are optimized separately for weight and cost under the design rules of Eurocode 3. Bending and shear resistances are considered, but lateral torsional buckling is neglected. Hybrid beams, where the flanges and the web may be of different steel grades, are also treated. The cross-section can belong to any of the four classes of Eurocode, which means that both plastic and elastic design is considered. The cost function takes into account fabrication, transportation and erecting the beam on site. The results indicate that while significant weight reduction can be obtained by high strength steels, rather limited cost savings are achieved compared with S355. On the other hand, hybrid cross-sections display promising potential as the most economical solution.