Learning how to anchor pallet racks is akin to mastering the art of constructing skyscrapers. Just as skyscrapers rely on being securely anchored to bedrock to withstand formidable lateral wind and seismic forces, the stability of a rack system hinges on its anchors. Much like a skyscraper’s foundation determines its resilience, the connection of a rack system to the concrete floor is paramount for ensuring stability.
All racking will experience real-world loads that will try to pull out or shear the anchor bolts being used to connect the base plates to the concrete floor. This happens when stocks are being stored or removed, when unexpected load shifting occurs, when accidental forklift strikes occur, and when there is any seismic activity. Regular inspection of racking should always include a professional inspection of all rack anchors.
At Mac Rak, we have engineered racking repair systems that are stronger than the original structures being replaced, the strongest in the industry. Of necessity, everyone involved with racking installation, maintenance, and repair should understand pallet rack anchoring standards for properly anchoring rack to the floor to achieve engineered ratings.
Anchors and Warehouse Rack Collapse
Ng, Beale, and Godley found in their analysis on rack failures that anchors can play a big role in converting a localized collapse into the “domino” effect or “unzipping” of the structure for an entire rack system. This is known as a “progressive collapse” of a racking structure. In their computer static and dynamic analyses, these engineers found that…
3.3…whenever [other joints] or base-plate connections reached their maximum tensile yield forces they were assumed to have failed….
This had the dramatic effect of reducing the maximum loads by up to 67%….
Understanding how to anchor pallet racks is crucial for ensuring structural integrity, particularly under unexpected loads or in the event of damage or partial collapse. While delving into the intricacies of this subject is recommended for a comprehensive grasp (reading the paper is recommended), the essence is clear: the effectiveness of the anchors and the plates they secure to the floor is paramount. Should the anchors fail due to improper installation, damage, or the utilization of unsuitable anchors, the racks are susceptible to collapsing under significantly lower loads than their rated capacity. Such failures typically occur subsequent to an initiating event, such as beam-column joint failure or impact from a forklift.
Therefore, anchor bolt selection and proper installation are critical in how to anchor pallet racks.
Expected Loads
Real-world loads for pallet rack components is a complex topic. The rack components operate as a system, and rack failures often are primed by multiple system factors before a collapse. The load applied to the anchors is vital when choosing anchors or replacing anchors during rack repairs.
Concrete anchor systems used to anchor pallet racking will experience two types of loads:
- TENSION: where the rack is trying to “lift” the column, pulling on the fastener vertically. Seismic activity can also create tension as the ground heaves vertically and then drops suddenly.
Tension can also be created by a lateral force on the rack above the floor. When these lateral loads are offset from the floor by distance, one side’s base plates become the pivot, and the opposite side’s base plates get lifted… a “tipping” force. This lateral force can come from a forklift strike or pallet loading and unloading that does not clear the beams or shelving. The distance from the floor acts as the moment arm to create leverage and increase the pull on the anchor – the higher the point of the lateral force is on the racking, the more tension at the anchor. Horizontal seismic activity can also create this tipping force and, therefore, the tension on the anchor.
- SHEER: This is where the column is trying to shift laterally, typically from a forklift strike, creating a horizontal force right at where the base plate meets the concrete. That force is concentrated at this point like a pair of snips cutting steel – creating immense force across the shaft of the fastener at that point. Again, lateral seismic shaking can also create sheer at the anchors.
Both tension and sheer for a fastener are given at the “usable rating” – the approved, usable tension, or sheer. Most anchor manufacturers use a safety factor of 2.5 times the usable load to determine the maximum, failure rating. For example, a fastener with a sheer rating of 10,000 pounds should never be used in an environment where the expected sheer would exceed 10,000 pounds (if using a safety factor of 2.5). The anchor is not designed to be used in an environment that exceeds 10,000 pounds regardless if the ultimate failure rating is 25,000 pounds. See Seismic Design and Methods of Restraining Progressive Collapse resources.
See the example for anchor loads in the Pull-out Ratings / Tension Ratings section below.
Those loads at the anchors transfer from the columns attached to the footings. For rack repairs, it is essential to ensure that the newly repaired structure attached to the anchors is as strong as or stronger than the original structure. Some steel-grade loads are provided below for consideration.
How to Anchor Pallet Racks? Which Type of Anchor?
When considering how to anchor pallet racks securely into concrete, one encounters a myriad of anchor options. However, in the context of typical operating environments for pallet racks, three primary choices are commonly employed: screw fasteners, strike wedges, and wedge bolts. Each option comes with its own set of advantages and disadvantages.
Concrete Screws
Concrete screws may be removed, which makes them attractive for some racking installations. However, in typical rack functional conditions, a strike or lift to the column base plate can pull these out of the concrete. Because their means of securing the base plate is by their threads cutting into the concrete when they pull out, they widen the hole, and the hole becomes unusable. Concrete screws are not designed to be used in high-impact areas, and Mac Rak does not recommend using concrete screws for this reason.
Strike Anchors
Strike anchors have a sturdy pin inside a sleeve with a wedge at the bottom. They expand in the concrete hole when struck by a mallet, driving a pin to expand the bottom of the wedge into the concrete. Strike anchors are easy to install and can be removed easily by prying up the pin. However, they must be replaced if removed and typically have half the ultimate tension and shear ratings of our next fastener, bolt wedges. For this reason, Mac Rak does not recommend strike anchors be used.
Wedge Bolts
Wedge bolts hit the sweet spot of ease of installation, strength, and higher embedment depths than strike anchors, which further increases tension ratings.
Wedge bolts have a wedge at the bottom attached to the main bolt. The top of the bolt/stud has a nut and washer that must be tightened to the manufactures torque specification. The anchor bolt is driven into the concrete hole with a mallet until the depth when the nut and washer contact the base plate. After contacting the base plate, a wrench is used to tighten the nut until it has the correct torque, and that torque is specified to open the wedge enough to achieve the engineered tension capacity. Wedge bolts must have precise hole sizes (the same as their diameter when using ANSI-sized bits) and be torqued to the manufacturer’s specification to achieve their engineered ratings.
Wedge bolts are designed as “slip” anchors when the anchor has been subject to a force that exceeded the maximum usable load, the anchor nut is loose and the anchor still remains more than 50% in the hole, they can be driven or pounded back into the hole and retightened to the specified torque, reestablishing the rated tension.
For these reasons, especially when repairing damaged rack columns using Mac Rak’s engineered solutions, we only use wedge bolt anchors due to the high impact environments in which repair kits are installed.
Base Plates
Most racking base plates come with multiple holes to allow for various bolt placements. When drilling, if we hit rebar, we’ll need to select a different hole.
It is important to follow the OEM requirements for the number of anchors and fastener specifications when learning how to anchor a pallet racks column to the concrete floor. The base plate holes are typically 9/16″, 11/16″ or 13/16″ for 1/2″, 5/8″ or 3/4″ anchors respectively, depending upon the engineering specifications of the rack manufacturer.
It is critical to space out the anchors and not place them too close together. Anchors are recommended to be spaced a minimum of 8 times the diameter of the anchor apart from each other (1/2” anchor must be no closer than 4” center to center away from the next closest anchor, ¾” anchor requires a minimum spacing of 6”.) otherwise, the anchor will apply too high of a concentrated load to the concrete, and significantly de-rate the usable anchor rating, by as much as 90%. In this case, it would be pointless having two anchors when together, they would have the strength of less than one anchor.
Available for Download
Download your free User Guide for Inspection of Damaged Storage Rack Systems booklet now. Great for use on PC or to print out.
Thicker Steel Foot Plates Increase Impact Resistance
Understanding how to anchor pallet racks involves considering the thickness of the steel used in the anchor plate, which is a critical factor. Opting for thicker steel foot plates enhances the shear resistance of the anchors. Increased shear resistance directly correlates with greater impact resistance for the entire rack system. Additionally, it’s essential to select a foot plate that complies with potential seismic engineering standards applicable in your region, often necessitating an even larger and sturdier footplate. Generic parts may not adequately fulfill all these requirements.
Upgrade the Anchor Bolts – Mac Rak uses 3/4” X 7” wedge bolt anchors on all of our repair products except our Frontline repair kits. ¾” X 7” anchors have a usable tension resistance of approximately 10,200 pounds per anchor, depending on the PSI of the concrete into which the anchor is installed. 7” anchors with a 5-1/2″ embedment have twice the tension resistance of 5” anchors with a 3 1/2″ embedment because the 7″ long anchors are applying the tension load, pulling from the middle to the bottom of the concrete slab and not the middle to the top of the slab as 5″ long anchors do. Mac Rak always uses ¾” X 7″ long wedge bolt anchors due to the extremely high impact that our Advantage and Elite kits are engineered to resist.
How to Anchor Pallet Racks with Mac Rak Repair Kit Upgraded Anchor Points
All Mac Rak repair kits (except Frontline repair kits that use ¼” thick footplates) come standard with 3/8” thick footplates and multiple 3/4″ x 7″ anchors to ensure that your new anchor points are solid and that they exceed required engineering. Displacement on impact resistance is enhanced by a solid foundation of anchors provided by robust anchor footplates and anchor bolts from Mac Rak. The upgraded bolts included assist in how to anchor pallet racks the right way.
Always consult your as-built drawings and your Mac Rak installation kit instructions for number, spacing and size of anchor wedges. Use Rack Load Capacity Plaques And LARC Drawing
How to Anchor Pallet Racks with Embedment Depth
Wedge bolts have a tension rating that increases with embedment depth. Of course, the longer the bolt, the deeper the embedment. The deeper the embedment, the stronger the tension rating. Mac Rak uses 7” bolts (¾” diameter) in our repair solutions, except for our lightest-duty single leg Frontline product. This provides for over 5” of embedment depth, typically 5-½”. Embedment depth increases the usable tensile strength of the wedge bolt. Concrete is strong, and typically a minimum of 6 inches deep, but it is weakest in shear. As a bolt is pulled vertically, strain lines are creating internal shear from the bottom of the wedge to the top of the concrete. You can think of these strain lines running in various angles up to 45 degrees from the vertical of the bolt hole. The concrete in this zone provides strength against pull-out.
The deeper the embedment, the more concrete will be in this inverted conical area, and its radius increases with the square of the embedment depth. The volume of concrete providing strength against pullout increases by the cube of embedment depth! This creates much, much more strength with only an inch or two of additional embedment.
How to Anchor Pallet Racks with Anchor Spacing
Concrete anchors are only as strong as the concrete to which they attach. Because concrete is brittle in sheer, there needs to be a significant distance between each anchor to provide enough concrete surrounding each fastener. Further, fasteners can create combined loads on concrete, so they need to be far enough apart that these loads don’t degrade the tension ratings of the bolts based on a diminishment of the anchoring due to combined loads.
Make sure to follow the manufacturer requirements for your anchor spacing, but generalized minimums would be:
- Minimum inter-fastener distance: 8 times the fastener diameter
- Minimum distance to the unsupported edge: 5 times the fastener diameter
Pull-out Ratings / Tension Ratings
Mac Rak engineered rack repair systems are designed with the highest industry ratings for tension and sheer at the base plate. We only use (and always recommend, to maintain our first-in-class lifetime warranty) ¾” x 7” wedge bolts for 5-1/2” of embedment in all our solutions, except for our lightest-duty single leg Frontline product, where we use ½” wedge anchors. Lighter duty racking systems may use ½” wedge bolts with lengths of 4-1/2” to 5”, providing a minimum 3” embedment.
The following table provides approximate tension and sheer ratings for typical anchors used in racking installation. Mac Rak anchors included with our solutions should never be substituted with another anchor. Our systems are precisely engineered to be stronger than the original racking, and this requires the included anchors.
How to Install Anchors for Pallet Racks
The following best practices should be used when installing wedge bolt anchors:
- Make sure racking and engineered repair kits are plumb and square before anchoring. Any changes in racking may affect the bolt location.
- Use the hole pattern in the base plate as a drilling template.
- Drill holes utilizing a hammer drill and the correct carbide masonry bit. Be cautious to not damage the base plate or drill through it. It is recommended you drill the holes at 14 degrees from vertical to provide a) space for the drill and b) increased pull-out strength for the two or more anchors. The drill bit diameter should be the same diameter as the wedge anchor (ANSI standard bit). (Mac Rak has only one manufacturing specification and testing data that an anchor installed up to a 15° angle has a higher tension ensure rating than an anchor installed at 90°, vertical)
- Next, clear out the holes. A vacuum or compressed air is easiest.
- Place the washer onto the anchor bolt stud and thread the nut on the bolt. Turn the nut down 1/4″ lower than the top of the anchor bolt stud (this protects the nut from being impacted and damaged when the anchor bolt is driven/pounded into the hole).
- Insert the assembled wedge bolt anchors into the drilled anchor holes.
- Using a hammer or mallet, cautiously pound the anchors into the hole until the washer and nut contact the base plate (5-1/2” for most Mac Rak engineered solutions).
- Go back and tighten each nut using a torque wrench to the OEM specification.
Reinstallation of Wedge Bolts
When inspecting racking, or anytime it’s noticed, if a wedge bolt has been pulled out of the plate by a forklift strike by 1” or less, you may attempt to re-tighten the knot to OEM specification. First, follow your procedure for notification and documentation of racking damage. Before starting, inspect the columns, beams, cross bracing, and shelving for damage, and order repair systems as needed to replace the damaged parts. Columns with less than ½” displacement do not require replacement.
If there is no damage to the racking, then you may attempt to reinstall the wedge bolt, as follows:
- Clear the racking of any impediments or products that would create a hazard.
- If there is any serious pull-out of concrete or the concrete is cracked around the bolt, do not attempt reinstallation.
- If there is minor concrete dust around the pulled-out bolt, vacuum it up.
- Unscrew the nut until it is 1/4″ below the top of the anchor bolt stud.
- Using a hammer or mallet, pound the bolt in until the nut is re-seated.
- Using a torque wrench, tighten the nut to the specified torque. If specified torque is achieved, and the concrete is intact, then the anchor bolt will have the rated usable tension.
- If you cannot achieve the specified torque, you will need to follow your procedure to install a new anchor in another base plate hole.
When Repairing Racking
The following are critical for the safe installation of repair systems using anchors, such as those from Mac Rak:
- Never re-use anchor holes (in most cases)
- Drill holes at correct diameters using ANSI carbide-tipped bits of the same diameter as the anchor.
- Use the OEM-supplied wedge bolts for your repair.
- Drill new holes at 15-degree angles during the repair
- Make sure to tighten the anchor bolt notch to the OEM torque specifications – relocate a new anchor if proper torque cannot be achieved.
OSHA How to Anchor Pallet Racks Requirements
OSHA does not have specific guidelines for warehouse racking safety or how to anchor pallet racks. However, the general clause of the Occupational Safety Health Act requires employers to provide a workplace free from recognized hazards. Proper installation of pallet racks is essential for safety. Posts and braces must be anchored according to the OEM specifications to avoid safety violations. OSHA does not specify exact standards themselves. They use industry standards for their references from American National Standards Institute (ANSI) standard MH16.1-2012. Heavy fines can be levied by OSHA for violations. So it is best to consult with knowledgeable professionals like Mac Rak to avoid all of the headaches, fines, safety hazards, and dangers of improper pallet rack anchoring. Stay safe and stay in compliance with Mac Rak.
Whether a skyscraper or a pallet rack, it’s only as good as its anchor to the foundation. By thoroughly inspecting, replacing, or installing racking anchors, Mac Rak creates a stronger, safer environment that resists loads of daily use, occasional accidents, and seismic motion.
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