Experimental and numerical investigation of welded hybrid steel box‐section girders

Abstract High‐strength steels (HSS) are increasingly used in structural engineering, particularly in long‐span bridges and tall buildings. Simultaneously, hybrid structures combining HSS and normal‐strength steel (NSS) are gaining popularity due to their efficient material usage. In hybrid girders, high‐strength steel is placed in the flanges to resist bending moments, while the webs are made of NSS, which adequately resists shear forces. This configuration allows for reduced cross‐sectional dimensions, more slender structures. These benefits translate into material savings, lower transport and construction costs, and reduced CO 2 emissions. However, the theoretical and practical framework for such hybrid girders is still limited in the international literature. Therefore, a combined experimental and numerical research program is carried out, focusing on the bending and bending‐shear resistance of hybrid box‐section girders. Six full‐scale laboratory tests are conducted, and a total of 20 numerical models are evaluated (12 under pure bending and 8 under combined bending and shear), also incorporating data from previous experimental studies. The flanges use S700, S500, S460 or S355 steel, while webs are made of S355 or S235; reference specimens are homogeneous girders made entirely of S355 or S700. This study presents the detailed test setup, failure modes, resistance values, and results of numerical tests.