Abstract. This paper presents the calculation of the cross-section of an RC rod element strength under the quasistatic lowcyclic loadings, considering the non-linear stress-strain relations of materials without cracks. Some mathematical models of the limit and shakedown analysis proposed by the authors involve the technique of calculating the cross-section under one-path loadings, considering the non-uniqueness of problem solutions. The plasticity conditions for the materials of the cross-section are formulated either in stress or in strain space. Simple solutions of two types, direct and inverse, corresponding to the limit states for alternating plasticity or progressive failure, are considered for the non-linear optimization problems obtained.