Cross-Aisle Seismic Behaviour of Drive-In Steel Storage Racks

Abstract

Many storage racks fail during earthquakes. Investigations of previous earthquake incidents reported that failures in storage racks were either because of inadequate structural design or because racks were struck by heavy pallet loads falling from the racks as pallets moved and dislodged during the earthquake. This has highlighted the need for robust earthquake design guidelines for steel storage racks. Therefore, the main objective of this thesis project was to study the seismic behaviour of drive-in racks, and particularly to derive the ductility factor for the rack in the cross-aisle direction. Since the seismic response of structures in general and storage rack in particular depends primarily on the characteristics of the ground motion, a comprehensive study was completed for determining and choosing the appropriate earthquake signals to be used in the research. State-of-the-art 3D finite element numerical models were created for studying the nonlinear behaviour of drive-in racks under seismic loads. The models were used to carry out parametric studies on drive-in racks using numerous earthquake records, and several structural systems. Non-destructive earthquake tests were conducted for determining the dynamic properties of drive-in racks. These included the natural frequency, fundamental period, and damping. Destructive earthquake tests were carried out on drive-in rack systems in order to examine their behaviour in the cross-aisle direction. The test results provided an understanding of the 3D behaviour of the cross-aisle frames, defects in the systems used, and areas of improvements. Also, from the destructive tests the ductility of drive-in racks in the cross-aisle direction was determined. Based on the shake table test results and the nonlinear time history dynamic analyses, a “static” type design approach using the equivalent static force concept has been developed to design drive-in racks in the cross-aisle direction