Impact tests, parametric impact studies and design impact forces on drive-in steel storage racks (No. R903)

Abstract

Extensively used in the industry to store goods, storage racks are frequently subjected to accidental impact forces from operating forklift trucks. There is currently little understanding of the nature of these impact forces, leading to occasional catastrophic failures because of inadequate structural design. International racking design codes deal with impact but use an arbitrary value of impact force with no scientific justification. This report focuses on an impact-sensitive type of storage rack, called “drive-in racks”. Contrary to classical “selective racks”, where pallets are stored on beams and where each single pallet is always accessible; “drive-in racks” allow the forklift truck to drive into the rack to store pallets on rail beams, one after each other, on the first-in, last-out principle. This type of design leads to slender uprights in the down-aisle direction, only restrained at the base and at the top. When subjected to an impact force, the bowing of the upright triggers progressive failure by allowing the pallets to drop through. This report presents experimental test results from impact tests on a complete full-size drive-in rack structure. Six series of twenty tests each, representing three pallet loads and two rack loading configurations have been conducted by striking the drive-in rack by a forklift truck. Parametric impact studies using finite element analysis are also presented. Factors affecting the sensitivity of drive-in racking structures to impact are investigated and conclusions are drawn about the parameters most significantly influencing the progressive collapse of this type of rack under impact. Based on a reliability analysis, realistic design impact forces formulas are proposed.