Stability Analysis of Unbraced Steel Storage Racks: Discussions and Alternatives

This paper aims to evaluate simplified methods used to perform frame stability analysis; effective length method and direct analysis method are compared as alternative to analyze irregular unbraced steel pallet racks. Steel storage racks are composed by: perforated thin-walled steel profiles, beam-to-column hook-in connectors, and base connections; the structural analysis of these systems shall consider semi-rigid connection between the elements and global, local, and distortional buckling in perforated profiles. Herein, the direct analysis is carried out according to AISC and AISI design standards, whereas the effective length analysis is performed according to the steel rack design specification. Advanced analysis is carried out for typical unbraced steel storage rack using finite element model and beam elements; geometrical and material nonlinearities, as well as initial geometric imperfections, semi-rigid beam-to-column, and base connections were taken in account. Comparative analysis indicates that the direct analysis method is an advantageous alternative to the effective length method. Since beam element models are not able to predict local and distortional buckling, we, herein, propose the use of lattice models to take these buckling modes in account while still only using beam and truss elements in the analysis. The results obtained using lattice models are shown to be an effective alternative to analyze large steel frames with complex interaction between the elements and subjected to local and distortional buckling.

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