Deflection Control and Code Provisions

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Title: Deflection Control and Code Provisions

Author(s): R. I. Gilbert and B. V. Rangan

Publication: Special Publication

Volume: 86

Issue:

Appears on pages(s): 121-136

Keywords: beams (supports); building codes; concrete slabs; deflection; flat concrete slabs; one-way slabs; reinforced concrete; span-depth ratio; serviceability; structural design; thickness; two-way slabs.

Date: 8/1/1985

Abstract:
Deflections can be controlled by limiting the span-depth ratios of flexural members. In the first part of the paper, the allowable span-depth ratios specified by the ACI Code, the CEB-FIP Model Code, the British Code, and the Australian Code are reviewed. It is found that the provisions of the ACI Code and the CEB Code are too limited, and the methods of calculation given in the other two codes are too detailed. All the four codes have an important drawback in that it is not known what deflections will result if the allowable span-depth ratios are used in design. The second part of the paper briefly outlines the authors' recent research in which suitable expressions for allowable span-depth ratios are proposed. The last part of the paper includes several numerical examples to illustrate how the new proposals can be used in design.