Accurate assessment of pallet rack capacity is crucial to ensure a safe warehouse.
Unfortunately, many overlook its importance or use oversimplified methods that don’t take into account all of the necessary factors.
The repercussions of which can be far-reaching, leading to permit delays, inefficient storage practices, accidents and potential legal consequences.
This article aims to address this problem by providing a thorough understanding of pallet racking weight capacity, offering solutions for accurate calculations, and introducing an innovative tool, OneRack, designed for swift and precise determinations.
What Is Pallet Racking Weight Capacity?
The capacity of pallet racks is the maximum load a rack system can safely support.
However, it is important to acknowledge that this capacity is not a one-size-fits-all metric.
Numerous factors contribute to the nuanced nature of pallet rack weight capacity, such as material grade and thickness, geometry of the rack, and even project location and slab thickness and strength.
We’ll go on to dive deeper into each one but please note that there are many variables that affect capacity.
Capacity Charts
If you haven’t seen capacity charts before, they are tables that show the capacity of beams and frames based on variables like beam length and shelf spacing.
But here’s the problem: They overlook variables that greatly affect capacity.
On every capacity chart, you’ll see a subnote saying something like, “Capacities are valid for static loads only.”
What does that mean?
It means that if all you had to worry about was the weight of the product, then the capacity in the chart is correct for their standard products.
The reality is that the weight of the product is never all you have to worry about and sometimes the rack you want to know the capacity for isn’t a standard product.
Every rack is required to be designed for seismic loads. A common misunderstanding is that some areas are seismic and some aren’t.
That’s not true; Some areas are higher seismic than others, but every project location has seismic criteria that needs to be taken into account in the determination of the capacity of the rack.
This is why you never only have to worry about the weight of the products. The seismic criteria of the project location always has to be considered, too, which is why using the capacity from the charts to design your rack is inaccurate and dangerous.
Capacity charts really best served as just marketing tools that manufacturers put in their brochures to show that their materials were just as strong as their competitors, but they were never meant for designing your rack.
This doesn’t mean finding the capacity of storage racks needs to be difficult.
OneRack, an innovative software created by structural engineers, was created to solve this very problem.
Using OneRack, any rack professional can input simple criteria and the software will provide accurate capacities.
We’ll tell you more about OneRack in this article, but first let’s break down some of the focus points when the capacity of a pallet rack is being determined.
Understanding (and Improving) Pallet Rack Weight Capacity
The calculation of pallet rack weight capacity is a fairly complex process. But in this section, we’ll dive into the components—and give you some helpful tips to optimize your weight capacity.
To discuss the calculations behind the capacity of storage racks, it is best to break the rack down into its individual components.
Properties and Material
The geometry of each component determines its properties (known as section properties) used in calculating the capacity.
Determining these properties can be complex, which is why they are usually calculated using software.
Also material grade is a significant factor affecting the capacity of the rack. Material grade is basically the strength of the steel being used to make the components.
A36, A572 Gr50, and A1011 HSLAS Gr55 are some examples of material grades we see in the industry.
This can be seen on the mill ticket for the raw material purchased before manufacturing the rack products.
Beams
Beams are designed in accordance with the ANSI MHI 16.1. Their capacities are affected by their section properties, the material grades, the stiffness of the connector to the column, the length of the beam and number of pallets.
The overall dimensions and thickness of the beam affect its section properties. These section properties affect the beams resistance to bending when put under load.
Improving your capacity: The stiffness of a connector affects the beam’s capacity. So, using a 4-pin connector instead of a 3-pin could increase the capacity of the beam.
The length of the beam affects the capacity, because the longer it gets the more bending it will see. This also means that longer beams will deflect more. The code limits beam deflection in our industry to L/180 (length of the beam divided by 180).
Improving your capacity: The number of pallets on the beam affects the capacity. This is because of something called Impact Load.
The code requires that 25% of the weight of one pallet be induced as an extra load on the beam, in the case of impact from a forklift or a forklift forcefully placing the load on the beam.
So if you have two 2500lbs pallets on a shelf, the beams are seeing less design load than if you had one 5000lbs pallet on the shelf.
OneRack, a software that designs storage racks in minutes, takes this into consideration automatically.
Frames
Frames are also designed in accordance with the ANSI MH16.1. Frames can be broken down even further into columns and braces.
The capacity of which is affected, again, by section properties and material grade. Column capacity is what has the most influence on the frame’s capacity.
Columns’ capacities are also affected by the beam spacing, panel dimension (brace spacing), and the perforations (holes) in the column. The reduction in capacity of the column caused by the perforations is determined through testing.
The tests produce something called a “Q value” that is used in the engineering equations to determine the capacity.
The braces in a frame help stabilize the column from buckling. The more those braces are spaced out in a frame, the less they help stabilize the column. Beams play a similar role in that they help stabilize the column from buckling.
Improving your capacity: A common way to increase the strength of a column is to add reinforcement (a backer), which is most commonly the addition of another column welded to the existing column.
Improving your capacity: Reducing the panel spacing in a frame can be a cost-efficient way to increase the capacity. This increases the columns’ resistance to buckling and could keep you from having to add a backer or increase the size of your column.
Seeing this in action is easy using OneRack, as all of the panel spacing is easily changeable, showing you the capacity in real time.
The braces play an important role in addition to stabilizing the column. They transfer seismic loads through the frame. This is why you may need to upsize brace sizes in higher seismic areas.
Base Plates and Anchors
Believe it or not, these could be the trickiest and most troublesome components in determining the capacity of your rack.
You can have the beefiest frames and beams, but if you have inadequate base plate and anchors, your rack can’t reach its full capacity.
Base plate capacity is affected by the overall dimensions, thickness, material grade, and even the size of the column and spacing of the anchors.
Anchor capacity is affected by the size of the anchor, the strength and thickness of the slab, the base plate thickness, as well as tested values.
Base plates serve two main purposes; 1) They transfer downward forces to the slab and 2) they transfer upward forces to the anchors.
The thickness and overall dimensions are variables that have most influence in its ability to effectively transfer loads, but they should be determined in harmony with the anchor design.
The anchors’ primary purpose is to keep the rack from overturning during a seismic event and are designed in accordance with the ACI 318.
Sometimes increasing the anchor diameter is enough to achieve sufficient capacity, but other times it may be the quantity, the spacing or the embedment of your anchors.
Many of these variables affect how the concrete will break out when there is an upward force in a seismic event.
Improving Your Capacity: Decreasing the base plate thickness or overall dimensions may increase the capacity of the anchors. This design approach, in accordance with ACI 318, uses the base plate as a “ductile member”, that helps dissipate energy in a seismic event before it gets to the anchors.
OneRack performs this analysis instantly, ensuring you’re provided with the most efficient base plate and anchor design.
This seems like a lot, right?
Well you’re not wrong.
The good news is that OneRack takes all of this into account automatically. You don’t have to worry about any of it. In the next section we’ll discuss how OneRack will help you determine rack capacities efficiently and accurately.
How to Use OneRack to Calculate Your Pallet Rack Weight Capacity (Within Minutes)
To use OneRack, you don’t need to know any more information than what you need to know to use a capacity chart.
First you create a project, where OneRack will use the project address to determine the seismic criteria for that specific location.
Next you’ll select a rack manufacturer and start loading up your rack. It’s as easy as clicking a few buttons.
AND THAT’S IT! From there you know your capacity. You can generate a comprehensive prelim document to use to order, compile counts, etc.
Did You Know You Can Create Winning Storage Rack Prelims, All by Yourself?
Thanks to OneRack, now you can get prelims approved in minutes. No more weeks of back-and-forth with engineers.
Tweak your prelims in the app until you get it exactly how you want it, and then send the finished product off for a permit.
And the best part? You can try it for free for a limited time with this link.