Concrete Anchor Bolts: Why These Little Components Are A Big Deal

 

“Rack columns not anchored to the floor” is a major racking issue that OSHA frequently cites under the General Duty Clause of the OSH ACT which states employers are required to provide their employees with a place of employment that “is free from recognizable hazards that are causing or likely to cause death or serious harm to employees.” That’s a pretty broad requirement!

There is, however, a reference document that is often used by OSHA in conjunction with the General Duty Clause to cite employers for pallet racks and other types of industrial steel shelving that are not adequately secured. That document is ANSI/RMI MH16.1 – Specification for the Design, Testing and Utilization of Industrial Steel Storage Racks. Section 1.4.7 of the specification states:

The bottom of all columns shall be furnished with column base plates, as specified in Section 7.1. All rack columns shall be anchored to the floor with anchor bolts, which shall be designed in accordance with Section 7.3, to resist all applicable forces as described in Section 2.1 or Section 2.2.

But before you rush out to purchase a box of concrete anchor bolts, it’s important you understand that the type of concrete anchors you choose to secure your pallet racks can affect the integrity of your entire system. In reality, you should use the anchors specified by your manufacturer or engineer for your particular application and building codes, but to understand why your little anchors are actually a big deal, let’s take a look at the different concrete anchor bolts available and how they are designed.

Types of Concrete Anchor Bolts Used for Pallet Rack

Wedge Anchor Bolts

One type of anchor bolt for securing pallet rack columns to the floor is a concrete wedge anchor. These anchor bolts are specifically designed for use in solid concrete and are available in a variety of diameters, lengths, and thread length. They can be fabricated from carbon steel or stainless steel.

Wedge anchors are placed into a drilled hole, then pounded in and fixed with a washer and nut. When the anchor is hammered into the hole, the bolt secures itself by using a mechanical wedging effect at the end of the fastener. Wedge anchor bolts can’t be removed; if you rearrange your pallet rack, you will have to saw off the top of the anchor so that it is flush with the floor.

Wedge anchors are effective when the concrete is in good condition and minimum spacing is preserved.

Strike Anchor Bolts

Concrete strike anchors can also be used when anchoring warehouse pallet racks. The strike anchor is an impact-expansion type anchor. An advantage of the strike anchor is that the nut and washer can be easily preset for the desired embedment and the installer knows that the anchor is fully set in the concrete when the pin is fully seated into the top of the anchor. Like wedge anchors, strike anchors are not removable. 

What Size Anchor Bolts Do You Need?

You should check on local building codes and/or have an engineer determine the anchor bolt sizes needed for the specific application. When you get your warehouse permitted, you will be informed of the size to use and how deep the anchors should be embedded. Here are some of the factors that determine anchor bolt size:

  • The weight of the element to be fastened to the concrete
  • The hole size in the upright’s baseplate (hole size is critical to the holding values of the wedge anchor).
  • The levelness of the floor (the wedge anchor is the only anchor that provides the necessary features for leveling and shimming).
  • Thickness of the concrete (avoid having the working end of the concrete anchor too close to the bottom of the concrete).
  • Hardness of the concrete
  • Seismic activity

About Holding Power

The holding power of any anchor is dependent upon the quality and strength of the concrete itself. The best holding values are achieved when the concrete is hard and the embedment is deep. The bolt’s diameter will also affect the holding values. When comparing technical data from different manufacturers, be aware of whether values given are for ultimate load ratings or working load ratings. Either type is okay, but be sure to use equivalent values when comparing bolts from different manufacturers. 

How Many Anchor Bolts Do You Need?

Although a standard baseplate will have two or more holes, they are normally just used for different placement options, not necessarily to anchor the rack column in more than one place. Usually you just use one anchor bolt per column; since they are so close together, using more anchor holes could weaken the concrete floor. With larger baseplates, however, you can have more than two anchor bolts – up to four. You should definitely check your building codes and consult with an engineer because the number of bolts you need can vary due to baseplate size, where you are located, or a variety of other factors. Seismic requirements will often call for special anchoring. 

Engineering and Design of Concrete Anchor Bolts

The ANSI/RMI specification states the anchor bolts should be designed in accordance with section 7.3, which states: “The anchor bolt design shall be in accordance with the provisions of ACI 318 Appendix D.”

So what is ACI 318 Appendix D? This is where things really get interesting, so stay tuned for our follow up post which will take a look at the exciting world of anchor bolt design! (Be the first to know –subscribe to our blog now to get the next post delivered directly to you email!)

We take every part of your pallet rack system seriously. From starting with high yield strength carbon steel (we can produce mill certificates for every piece of coil that we purchase) to superior engineering & product design for every inch and element of your rack system (including the anchor bolts!), to expert systems design & equipment integration, Next Level is committed to on-going quality assurance in the design, manufacture, sale and service of quality storage products. For more information on how we can help you increase efficiency and profitability, contact us here or call 800-230-8846 now to speak to a design expert.

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