Seminar - Benoit Gilbert - Determination of accidental forklift truck impact forces on drive-in steel storage racks and behaviour of these structures under impact
Wednesday 2 September 2009, 1.10 pm - 1.55 pm
Civil Engineering Lecture Theatre 3
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 seminar aims to calculate the impact forces developed between the forklift truck and the rack and focuses on an impact-sensitive type of storage rack, called “drive-in racks”, in which pallets are stored one after the other on the “first-in last-out” principle, leading to unbraced uprights in the impact direction.
Experimental test results from impact tests by a loaded forklift truck, on a complete full-size drive-in rack structure, are presented. Static and dynamic experimental test results on the isolated loaded forklift are also presented. Based on first principles of mechanics, simple models of the loaded forklift truck and the drive-in racking structure are presented. Model masses, as well as stiffness and damping coefficients are calibrated against experimental results. Comparisons between experimental results and solutions obtained from the simple mechanical models show that the simple models accurately reproduce the static and dynamic behaviours of their associated structures. Combining the simple mechanical models and the impact test results actual impact forces are calculated and presented.
Finally, using the now known nature of the impact forces, parametric impact studies using finite element analysis are 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.