Prediction of Deflections of Two-Way Floor Systems

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Title: Prediction of Deflections of Two-Way Floor Systems

Author(s): Amin Ghali

Publication: Structural Journal

Volume: 86

Issue: 5

Appears on pages(s): 551-562

Keywords: cracking (fracturing); creep; deflection; flat concrete plates; floors; shrinkage; slabs; stiffness; tension; two-way slabs; Design

Date: 9/1/1989

Abstract:
Inaccuracy in deflection prediction in reinforced concrete floors is caused by errors in the parameters related to material properties by the method of calculation. This paper attempts to eliminate or reduce the last source of error. The bending moments normally determined in design for column and middle strips are used to calculate basic deflection values using properties of the gross concrete section and ignoring the presence of reinforcement, cracking, creep, and shrinkage. These effects are accounted for by use of coefficients that are functions of the cross-sectional properties, modulus of elasticity of steel and concrete, creep, and aging coefficients. Simple equations are derived for the coefficients based on compatibility and equilibrium. A numerical example of deflection prediction is included.