While this is one of the most frequently asked questions, the answer is unfortunately, “it depends”. How much weight a rack system can hold depends on a number of factors including:
Load Beam Capacity:
The first step in determining a rack system capacity is what weight can each pair of beams hold. Beam capacity varies depending on beam material, height and construction materials. Most manufacturers provide standard load tables that can be used as a guideline. Published capacity charts are generally based on evenly distributed loads but do not take into account seismic or other special criteria.
While determining individual beam capacities are fairly straightforward, determining upright capacity is much more involved. First the engineer will look at the distance between the beam levels—Although counter intuitive, a system with 96” spacing between beam levels may have significantly less capacity than a system with only 48” between beam levels. We have seen cases where removing a beam level can reduce the capacity of the system from 2,500 lbs./pallet to 1,500 lbs./pallet. The engineer will then look at the total number of levels to be supported, the upright frame design, whether the frames are braced back to back, plus other factors.
Slab and Seismic Considerations:
The evaluation is further complicated when slab and seismic considerations are taken into account. Because the rack system will be anchored to slab, the thickness of the slab, soil and other characteristics must be taken into account. In addition, in virtually every state in the union, building permits are required and seismic considerations will have an impact on the rack design often requiring significant strengthen of the system to withstand seismic forces. Rack designed for high seismic (California and even Memphis), is normally made from much stouter material than non-seismic rack (Texas).
Always Use a Qualified Engineer:
Since there is no simple answer to rack capacity, always check with a qualified rack design engineer. The engineer will have the experience and calculation tools to ensure that the system that you select will provide years of safe operation. Insist on written calculations, accompanied by LARC drawings that show the specific configuration that you are installing. Stamped and sealed drawings are normally required to complete the building permit process.
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