Ductility Ratio for Slabs

A method is presented to calculate, approximately, the ultimate deflection of a reinforced concrete slab subjected to a point load at the center. This deflection is divided by the yield deflection, calculated by an approximate, but widely used method, to obtain a permissable ductility ratio for the slab. This ratio is useful in approximate dynamic analyses of slabs subjected to impulsive and impactive loadings. The method presented for the calculation of ultimate deflection takes account of the compressive strength of the concrete, the yield strength of the steel, the ratios of tensile and compressive steel in a cross section of slab, and the slab geometry. Thus, it is presented as a rational replacement for the empirical equations in current use. Comparisons with test data indicate that the method presented is reasonable and conservative.