Title: Deflection Calculation for Reinforced Concrete Structures—Why We Sometimes Get It Wrong

Author(s): R. Ian Gilbert

Publication: Structural Journal

Volume: 96

Issue: 6

Appears on pages(s): 1027-1032

Keywords: cracking (fracturing); creep; deflection; reinforced concrete; serviceability; shrinkage; slabs; time-dependent.

DOI: 10.14359/779

Date: 11/1/1999

Abstract:
The simplified procedures contained in ACI 318 for calculating the deflection of beams and slabs are inadequate in some situations. This is particularly the case for deflection sensitive elements such as floor slabs. The provisions in the current Australian Code AS 3600–1994, which are similar to those in ACI 318, have recently been found wanting in a variety of situations and are currently under review. The calculated deflection is often significantly less than the actual deflection, and serviceability problems resulting from excessive deflection are not uncommon for structures designed in accordance with the code. In this paper, the deficiencies of the existing approach are discussed and demonstrated by a comparison with experimental results. Suggestions for improving the procedure are also proposed and evaluated.