Simplified Computations for Effective Moment of Inertia Ie and Minimum Thickness to Avoid Deflection Computations

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Title: Simplified Computations for Effective Moment of Inertia Ie and Minimum Thickness to Avoid Deflection Computations

Author(s): Jacob S. Grossman

Publication: Journal Proceedings

Volume: 78

Issue: 6

Appears on pages(s): 423-439

Keywords: beams (supports); building codes; concrete slabs; deflection; flexural strength; lightweight concretes; moments of inertia; rectangular beams;reinforced concrete; serviceability; stiffness; structural analysis; structural design;T-beams.

Date: 11/1/1981

Abstract:
An approximate simplified procedure is described for estimating the effective moment of inertia I, for beams, T-beams, or one-way slabs constructed of normal weight aggregate concrete or lightweight concrete, and reinforced with 40-80 ksi reinforcing bars. The results are compatible with Ie values obtained from Eq. (9-7) of ACI 318-77. The simplified equations do not require computations for moment of inertia of the cracked section Icr, nor the reinforcing requirements initially. Also described is a simplified procedure for establishing minimum member depth so that deflection computations to ascertain serviceability may be avoided when designing the majority of one-way members.