Determining the proper frame capacity
1. Calculate the maximum load per bay by multiplying the number of levels by the load per level (supported levels only)
2. Determine the maximum distance between levels, or the distance from the floor to the first beam level, whichever is greater. This dimension is the “vertical beam spacing” or unsupported span. Weight capacities for upright frames are dependent upon this measurement.
3. Keep in mind that weight capacities also include the weight of the rack components themselves.
4. Refer to the rack manufacturer’s upright capacity tables which compare the type of upright to the vertical beam spacing to determine how much the frames can hold in total.
5. For weight capacities to be valid, pallet rack systems must be properly connected to the floor with the appropriate footplates.
Important: Be sure to verify the adequacy of your floor to support these loads.
Do You Need Roll Form or Structural Steel Frames?
Structural steel upright frames are what you might want if you are storing extremely heavy loads and/or your rack is in a very abusive or tough industrial environment. If your rack will be exposed to a lot of lift truck impact, is located outdoors or is in a freezer or cooler application, you will probably want to consider structural rack.
Roll formed upright frames are tough enough and strong enough for most warehouse applications. It is less expensive to buy and install–and if you don’t expect a lot of abuse, roll formed rack can be quite cost-effective. Consider using upright column protectors and end-of-aisle protectors to lessen the chances of forklift damage.
Don’t Overlook The Height-to-Depth Ratio
The height-to-depth ratio is an important factor in the specification; get this number wrong (or ignore it), and you risk your rack overturning. ANSI MH16.1 states:
The height-to-depth ratio of a storage rack shall not exceed 6 to 1 measured to the top loaded shelf level, unless the rack is anchored or braced externally to resist all forces. The height is measured from the floor to the top loaded shelf level and the depth from face to face of the upright column.
Furthermore, if the height to depth ratio exceeds 8 to 1, the racks should be stabilized using overhead ties. Other ways to deal with larger ratios can include other alternatives such as bigger baseplates, more anchors, or a combination of ties (examples: cross-aisle, ties to building structure plus base plate and anchors).
Regardless, if your height-to-depth ratio is over 6 to 1, you should have a rack engineer review the design and specify the appropriate anchors and baseplates to prevent tipping.