Abstract:
A satisfactory design of flat plate roof system requires the magnitude of deflection at
service load to be within the acceptable limit. Excessive deflection of reinforced
concrete flat plate can cause severe serviceability problems. Although deflection is an
important parameter in the design of structure, enough emphasis is not usually given in
the calculation of slab deflection as well as there is a tendency among designer to
reduce slab thickness to save volume of concrete and dead load of structure that also
increase serviceability deflection. Determination of flexural capacity with calculated
deflection magnitude within permissible limit may permit use of shallower section for
flat plate. The present study briefly reviews the methods available in literature for
calculation of deflection of flat plate and attempts have been taken to develop a method
to calculate the elastic deflection of flat plate for various end conditions.
With the aforesaid objectives in mind, a software analysis technique (using Finite
Element software, SAFE) has been used to study the behavior of deflection of flat
plates. The results obtained form the Finite Element (FE) models have been compared
with the ACI direct design method in order to check the reliability of the method. The
FE model has been used in the parametric studies of deflections and span ratios. The
results of parametric studies have been presented graphically as a basis of a unified
method for calculation of the deflection of flat plate for different end conditions.
Few test results arc available that were conducted to determine the immediate
deflection of flat plate. The deflection calculations of flat plate by the proposed method
have been validated by comparing against those test results. A range of ratios proposed
to determine the long term deflection of flat plate comparing the available long term
deflection of practical building with the elastic deflection determined the proposed
method.
