Long-time Multipliers for Estimating Two-Way Slab Deflections


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Title: Long-time Multipliers for Estimating Two-Way Slab Deflections

Author(s): Cameron J. Graham and Andrew Scanlon

Publication: Journal Proceedings

Volume: 83

Issue: 6

Appears on pages(s): 899-908

Keywords: concrete slabs; cracking (fracturing); creep properties; deflection; flexural strength; loads (forces); multistory buildings; reinforced concrete; shrinkage; two-way slabs; Structural Research

Date: 11/1/1986

A simplified procedure is presented for estimating deflections of two-way slab systems subjected to construction loads, shrinkage restraint cracking, irrecoverable creep, and other significant factors. The simplified procedure is based on long-time multipliers developed from a parameter study using an analytical model that can treat construction loading history as a series of load increments applied at specified times associated with particular construction sequence being used. The proposed calculation procedure results in higher calculated deflections than obtained by the current ACI and CSA design codes, as a result of the use of a reduced effective modulus of rupture and increased long-time multiplier. Calculated deflections are compared with field-measured deflections reported in the literature.