This paper describes the behaviour of selective steel storage racking systems in the cross-aisle direction. Steel storage racks are regular kind of equipment; these systems are developed for enhancing the storage of load units in diverse weights and sizes. In most cases in this study, the boundary conditions assumed fixed on their fundamental state, to prevent from any possible moment -rotation and uplift effects on uprights. Finite element method (FEM) modeling was used to analyze and evaluate the natural frequency of diagonally k-braced frame at cross-aisle direction. This report takes advantage of capabilities of two well-known structural analysis software for FEM modeling: Abaqus and Strand7. The objective is to predict and determine the eigenvalues and natural frequencies of selective steel storage racks in the cross-aisle direction. Taking the fact into account that the reaction of the structure under seismic loads is vitally important at this critical direction, this paper will provide a better view for designing these type of structures in the future. The novelty of this paper is to classify conditions where we could avoid creating any possible resonance in the structure. KEYWORDSSelective steel storage racks, natural frequency, cross-aisle direction, structural optimization, finite element analysis.