Closure to “Ultimate Strength of Ribbed Slab Composite Beams with Web Openings” by J. W. Park, C. H. Kim, and S. C. Yang

Abstract

In this brief article, Park, Kim and Yang reply to a commentary (Cho, 2005) on their research on composite beams with web openings. The beams studied have ribbed slabs with the ribs oriented transversely. The effects of slab width and moment-shear ratio on failure mode and strength were studied and the authors found that the failure mode of concrete slabs depends on the slab width. In the commentary article, Cho made four points: the authors misunderstood the truss analogy proposed by Cho and Redwood (1992); in the authors' study, the full slab width was assumed to be capable of carrying the vertical shear forces, even though this is not an ordinary understanding of the slab shear behavior; comparisons and evaluations should also include the predictions by the Redwood group methods other than the truss analogy; and the truss analogy predicts better narrow slab beams, rather than wide slab beams. The authors reply briefly to each of these points: the authors understand that the truss analogy considers the diagonal tension failure of the ribbed slab and the pullout failure of the studs interactively; the effective width of concrete slabs of composite beams was developed based on flexural behavior; in truss analogy, the resistance of the top steel tee was formulated based on the assumption of full composite action between the ribbed slab and the top steel tee; and the authors used beams with wide slabs in their tests because most beams had narrow slabs in the previous tests. The authors conclude by agreeing with the commentary author that more studies are needed for better understanding of the behavior of the studs at the bearing and anchorage zones, which are very important in the development of slab shear carrying capacity.