Experimental and numerical study on the flexural performance of U-shaped composite beams with cold-formed lipped channels

초록

This study investigates the flexural behavior of steel–concrete composite beams with a U-shaped section using cold-formed lipped channels as web members. Trapezoidal steel plates were attached to the lower side regions to enhance flexural capacity. Four specimens were tested under four-point bending, considering the presence of bottom tension reinforcement and the thickness of the side plates (6 mm and 8 mm). All beams exhibited a typical flexural failure mode. Specimens with bottom tension reinforcement showed higher flexural capacities, with the T6 and T8 series achieving increases of 19.1% and 14.8%, respectively, compared with the corresponding unreinforced specimens. In the present test configuration, top-flange stud connectors were provided to ensure composite action between the concrete slab and the steel beam, whereas the lipped channel webs contributed to composite interaction and shear transfer between the steel beam and the infilled concrete within the U-shaped section. Accordingly, the test results indicate the structural contribution of the lipped channel webs to the internal composite behavior of the beam, rather than the direct replacement of conventional stud shear connectors. Based on measured material properties, the plastic neutral axis was located within the concrete slab for all specimens. The experimental strengths were compared with design strengths calculated using KDS 14 and AISC 360, showing that the KDS method provides conservative predictions. A finite-element model was developed and validated, predicting ultimate strengths within 5% and accurately reproducing the load–deflection responses and failure modes. © 2026 Institution of Structural Engineers. Published by Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

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