Deflections of flat plate floors with irregular column layout

A procedure for calculating the instantaneous deflections of irregular reinforced concrete flat plate floors is presented. The method is applicable throughout the entire loading stages from the uncracked state to the fully cracked state and even up to the ultimate limit state. Based on the familiar effective moment of inertia approach, the proposed procedure also uses the ACI Direct Design Method with some generalization. The total static moment in a particular design strip will be distributed to the midspan and support sections according to the distribution coefficients of the ACI Direct Design Method, taking into account column sizes and irregularity of slab geometry around the edge slab-column connections. At high loads, the modulus of elasticity of the concrete can be reduced to better reflect the nonlinear behavior of concrete slabs. The definitions of effective span, width of design strips, torsional rigidity of transverse torsional members, and column sizes and orientations will be generalized as far as practical. The accuracy of the proposed procedure has been compared with measured deflections of two multiple-panel irregular flat plate floors tested at Nanyang Technological University - Singapore. The comparison between the calculated deflections and the experimental values shows that the proposed procedure is reasonably accurate.