A Study of Service Load Deflections and Ultimate Load Deflections of Flat Slab Structures


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Title: A Study of Service Load Deflections and Ultimate Load Deflections of Flat Slab Structures

Author(s): S. G. Gilbert, D. J. Cleland, and A. E. Long

Publication: Special Publication

Volume: 86


Appears on pages(s): 295-322

Keywords: building codes; columns (supports); cracking (frac-turing); deflection; flat concrete slabs; loads (forces); models; prestressed concrete; reinforced concrete; torsion.

Date: 8/1/1985

Results of an extensive experimental programme of tests to study the behaviour of both reinforced concrete and unbonded post-tensioned flat slab concrete structures are presented. The work has been carried out using very carefully designed and instrumented models of l/3 and l/4 scale. Particular attention has been given to correct control of the boundary conditions of the models such that the prototype multipanel structure is simulatedas accurately as possible. The effect of different variables such as column size, reinforcement levels, prestressing levels and layout of tendons on the load deflection characteristics of the slabs were investigated. The measured slab deflections have been:compared with the various code criteria, AC1 318-77 and CPllO Other research methods of predicting the deflection of two way slabs are considered and tested against the experimental data. The history of deflections beyond service loads up to ultimate loads is given and the changes in linearity are discussed and related to the cracking behaviour observed in the model structures.