This work addresses the influence of analytical instability on the obj
ectivity of analytical results in the application of the FEM to RC str
uctures. The main objective is to show that the principal causes of a
lack of stability in analyses lie in crack handling procedures and the
development of fictitious cracks resulting from FEA errors and inaccu
rate stress-strain calculations. To this end, the Ottosen models, (fai
lure criterion and stress-strain relationship) for monotonic and short
term loading have been employed. For simplicity full integrity betwee
n concrete and steel is assumed and the plane stress formulation only
has been considered.