Experimental and numerical study of two-hinged steel frames with cellular members

Abstract This study investigates the structural response of cellular steel frames, with particular emphasis on the influence of frame stiffness on failure mechanisms and load redistribution. Two steel portal frame specimens were experimentally tested under concentrated mid-span loading: a conventional solid-web frame (S01) and a frame incorporating cellular beams and columns (S02). The cellular specimen exhibited an increase of approximately 64% in ultimate load capacity and 48% in load at the serviceability deflection limit compared to the solid-web frame. A nonlinear finite element model developed in ANSYS demonstrated good agreement with the experimental results and was subsequently used to perform a parametric study investigating the effects of column stiffness, section size, and stiffener configuration. The results show that increasing column stiffness significantly alters internal force distribution within the frame, leading to higher bending demands in the beam while failure remains consistently governed by beam mechanisms, including plastic hinging and web-post buckling. The findings highlight that, under beam-dominated loading scenarios, improvements in frame stiffness enhance overall load capacity primarily through moment redistribution rather than increased column resistance. This study provides insight into the interaction between frame action and cellular beam behavior, contributing to the understanding of design considerations for steel frames incorporating cellular members.