Title: Collapse Load Estimation of Rectangular Reinforced Concrete Beam-Slab Systems—New Insights
Author(s): Bijily Balakrishnan and Devdas Menon
Publication: Structural Journal
Appears on pages(s): 1279-1294
Keywords: beam-slab failure; one-way bending; rectangular beam-slab system; slab-alone failure; tensile membrane action; two-way bending; yield line analysis
This paper revisits the design of simple rectangular reinforced concrete (RC) slabs, integrally connected to edge beams, supported at the four corners, and subject to gravity loads. Typically, the edge beams are made adequately stiff, whereby the slab can be analyzed and designed separately for two-way bending, considering the edges to be simply supported. This paper establishes, through yield line analysis and experimental studies, that the final failure is more likely to occur by a combined beam-slab failure—typically by one-way bending along the long-span direction, with plastic hinges forming in the middle of the long-span beams. The conventional yield line pattern (two-way slab-alone failure) will occur only in exceptional cases where the long-span beams are heavily reinforced. It is clearly demonstrated that the actual mode of failure and the collapse load are governed primarily by the relative beam slab strength in all cases, regardless of whether the edge beams are stiff or shallow. The proposed yield theory has also been validated by experiments on square beam-slab systems reported in the literature. These new insights on collapse load estimation of rectangular beam-slab systems can lead to more rational and economic strength design and detailing.