Investigation of collapsed rack storage systems

摘要

Several recent rack collapses suggest that the stability of the systems have not been fully understood by their respective designers because the designs do not fully comply with the sideways buckling provisions inherent in design specifications. The designers assumed the beam-to-column connections to be rigid and effective in developing moment frame stiffness. Similarly, the designers assumed the down-aisle bracing to have sufficient strength and stiffness to justify designing the rack as a braced frame. Collapses have occurred in rack systems fabricated with hot rolled steel shapes and in racks with thin gage steel sheet members that are cold formed into structural shapes. The investigations included testing of the connections to develop moment-rotation curves. Similarly, strength and stiffness parameters for the diagonal bracing were developed. The connection test data and bracing parameters were then incorporated in both traditional as well as finite element method analyses of the racks. Data from computer inventory systems precisely described the loading conditions at the time of the collapse. Although several collapses have been investigated, the emphasis of this paper will be placed on one project.