Progressive collapse analysis of beam–column substructures considering various reduced beam web sections.

In this study, beam–column connections with various web openings were prepared to improve the mechanical characteristics of welded steel frames. First, several specimens were constructed and tested after adding various web openings, including circular, square, hexagonal, semicircular, and elliptical web openings. We mainly focused on analysing failure modes, deflection shapes, load–displacement responses, and deformation capacities. The height, width, and position of the web openings were further studied through numerical simulations following experimental verification, and the results were compared for specimens with and without various forms of web openings. The catenary internal energies and contribution coefficients of the specimens with web openings were found to be greater than those of the base specimens; the values of the hexagonal and semicircular web openings were greater than those of commonly used circular openings. The bearing and deformation capacities initially increased and then decreased with increasing opening height. When only the opening distance b was changed, the load–displacement responses of the specimens overlapped in the elastic state; the bearing and deformation capacities increased with increasing b. We also found that the vertical loads of circular or near-circular web openings were smaller than those of polygonal openings with fewer edges. • Beam–column substructures with web openings are analyzed. • Progressive loading is applied to various test specimens. • Finite element models are developed based on the test results. • Various web opening parameters are analyzed in terms of vertical load. • Circular and nearly-circular openings are determined to be suboptimal. [ABSTRACT FROM AUTHOR]