» Read more recent posts about cantilevered racks and the latest version of ANSI MH16.3.
To ensure the safe design, manufacture and installation of cantilevered rack, RMI publishes the ANSI MH16.3 Specification for the Design, Testing and Utilization of Industrial Steel Cantilevered Storage Racks. The standard, which applies to cantilevered storage racks made of cold-formed or hot-rolled steel members, includes guidance on the rack’s safe design and use. It also covers racks outfitted with accessories such as decked shelves, shed roofs and canopies.
What is Cantilevered Rack?
Designed and engineered to store very long loads — such as furniture, lumber, steel bar stock, plywood, steel sheets, sheet rock, PVC piping, metal pipes and more — cantilevered rack structures incorporate a central, vertical column from which horizontal arms project outward. The arms extend from one or both sides of the central column.
Cantilevered storage rack is utilized both indoors and outside, and can be free-standing, top-tied, or integrated into the structure of the building to support the walls or roof. As with every rack system, to ensure the safe design, manufacture and installation of cantilevered rack, it is critical to engage a professional engineer with experience in racking to evaluate a variety of factors, including: installation site, soils, anchoring, load type to be stored, handling equipment, and more.
Also impacting cantilever rack design is the building’s geographic location. Seismic considerations for the rack vary depending upon the potential for damage from earthquakes in a region. Further, for outdoor application, the cantilevered rack designer will factor in the probability of an extreme snow, wind, hail or other weather event when calculating the strength and thickness of the materials specified to construct the system. These specifications lessen the likelihood of a system collapse during extreme weather.
Best Practices for Safe Use of Cantilevered Storage Rack
Whether the cantilevered storage rack is indoors or outside, there are several best practices surrounding its safe use. These include:
Routine Inspections
At a minimum, inspections of cantilevered rack should occur annually. However, inspections should occur more often for previously damaged racks or those in high traffic areas. Areas for examination (among others) include the condition of the loads in the system, the rack’s anchorage, column base plates, columns, bracing, arms and connections, and accessories.
Upon discovering a damaged section, the management should isolate the rack. Then, when safe to do so, operators should unload the rack. Do not use the rack until repairs or replacement of the affected portions are complete. Further, ANSI MH16.3 standard recommends initial — as well as repeated periodic — inspection of the anchor bolt installation to verify that anchors that are part of the main force resisting system are in place and secure.
Vertical Impacts
Care must be taken when placing or removing loads so as not to create an upward or downward impact that could dislodge or disengage the arm from its connection to the column. Additionally, the ANSI MH16.3 standard specifies that the arms and their connections be capable of withstanding an additional downward impact load of 25 percent of the handled unit load, and an upward force equal to 25 percent of the load.
Load Stability
Typically, cantilevered storage rack holds long loads. As a result, they often sag under their own weight during placement or removal. To provide additional support during load insertion and extraction, the rack installation may require a special attachment or type of material handling equipment. Alternately, the designer may incorporate additional horizontal clearance within each storage position. This is to accommodate the sag and prevent the load from striking the arms and weakening the structure during its movement.
Aisle Clearance
As the operator navigates a load down-aisle (or parallel to the load access face of the rack), they must pay attention to the amount of horizontal clearance between the load in transit and the rack arms. Although there are no vertical columns on the aisle side of the rack structure, the tips of the arms remain exposed. This puts them at a greater risk of a collision with a load, which could compromise their capacity and cause them to fail.
Learn More About Cantilevered Racks
Looking for more information about safe cantilevered storage rack design and use? Download RMI’s ANSI MH16.3 specification.
