A new technique for nonlinear analysis of reinforced concrete (RC) sla
bs under various lending programs is developed. The technique is based
on nonlinear finite element (FE) analysis of a grid representing the
slab. All original formulation for the representative grid allows a go
od quality of the representation for the most coarse mesh of the grid
awes. A refined nonlinear FE model of a RC frame under complex loading
was used. The model is based on a new modification of spatial anisotr
opic beam finite element and refined constitutive models of concrete a
nd steel-in-concrete under complex loading history. The developed simp
lified method is capable of predicting nonlinear behavior up to the fa
ilure for various RC slabs subjected to monotonic and complex lending
(including unloading and reloading branches). Slabs with different bou
ndary conditions, geometry,, reinforcement, and material properties ca
n be analyzed. Membrane action and influence of nonideal boundary cond
itions are treated. Analytical results for various RC slabs rested by
different investigators under different programs show a good agreement
with the experimentally observed data.