Evaluation of deflection performance of sizing-optimized cold-formed steel beams with various cross-sections

Turkish

Strength-based optimization of cold-formed steel (CFS) sections is a common strategy to enhance material efficiency, but it often results in slender profiles where serviceability performance is a concern. This study investigates the deflection performance of three distinct CFS profiles—a lipped channel, an unlipped channel, and a built-up I-section—after they were sizing-optimized (via parametric scaling) for strength limit states according to AISI S100-16. The final optimized dimensions for both secondary beams and girders were evaluated against the serviceability criteria of the International Building Code. A numerical analysis based on the conjugate beam method was employed, which accurately accounts for the variable effective moment of inertia along the beams’ spans. The results demonstrate that all six optimized sections comfortably satisfy the deflection limits for both live load (L) and total load (D+L) conditions. A comparative analysis revealed that while the lipped channel section was the most materially efficient, it exhibited greater, though still acceptable, deflections compared to the heavier unlipped and I-sections. This study contributes by quantitatively demonstrating that CFS beams optimized solely for AISI S100-16 strength limits can inherently satisfy IBC serviceability criteria, confirming the viability of this optimization approach in practical floor design. The findings confirm that a well-executed strength optimization does not compromise serviceability and that the lipped channel section provides an optimal balance between material economy and structural performance for the floor system studied.