Warehouse Collapse and 2 Keys to Prevention

A catastrophic warehouse collapse is the nightmare of warehouse owners and managers. The fallout is an even greater tragedy. Loss of life is at the top of the list. No one wants to have that on their conscience; especially if the catastrophe could have been avoided by proactive decisions. Loss of production and products is potentially massive, especially in these dire times of supply chain crisis. Then there are the legal repercussions, lawsuits, insurance investigations, government fines and penalties, and even jail time if gross negligence can be proven. Enormous consequences, yet the path that leads to this catastrophic point is often paved with a thousand small choices rather than one big mistake.

Learn to spot the mistakes that accumulate and make your racking vulnerable to catastrophic failure.

2 Keys to Preventing Warehouse Collapse, You May Have Overlooked

There are two keys to preventing warehouse collapse. First, we will examine the tiny missteps you might overlook that collectively “prime” a warehouse for collapse. Second at the end of the article, we will reveal the trigger events that set off catastrophic warehouse collapse.

But first, here are several videos that you may have seen before that show the catastrophic effects of racking failure. However, what you might not see in the video are the more minor mistakes that lead to this devastating outcome and the hidden forces that we are often unaware of that lead to racking collapse.

Table of Contents

1) Warehouse Collapse Due to Resonance Frequency Effect

Notice how a beam impact sends a resonance impact wave up the frame, and it collapses from the top down.

2) Warehouse Racking Collapse Due to Loading Issues

A pallet rack that collapses sideways is usually due to the collapse of a lower column. Racks can then impact adjacent aisles. Solo aisles are more vulnerable to this.

3) Warehouse Shelving Collapse Due to Improper Installation Collapse

Overloading upper shelves can lead to horizontal collapse as well.

4) Forklift Warehouse Fail Due to Lack of Rack Guards

Forklift impacts can take down pallet racks. The force of a heavy vehicle is immense and is often compounded by priming errors discussed below.

5) Forklift Warehouse Collapse Due to Failure to Inspect

Often racks will collapse toward the source of impact when it is a column failure.

HERE IS HOW YOU CAN PREVENT WAREHOUSE COLLAPSE

The Small Mistakes that Prime a Warehouse Collapse

Each time one of these small steps is missed, your warehouse is one step closer to the tipping point that could trigger a massive collapse. First, we will examine the small priming events that can prime your warehouse for disaster. Then later, we will examine the trigger events that can lead to a total collapse. 

Engineer of Pallet Racks
Sal Fateen has over 40+ years of experience in engineering for the pallet rack industry. He is the founder of Seizmic Inc.

Part 1: Mistakes That Prime Warehouses for Failure

According to one of the world’s leading engineers of Pallet Rack systems, Sal Fateen, most warehouse incidents have priming errors. These are mistakes that seem to not cause any real issues and are easily overlooked. The rack has been like that for years, we’ve been doing that for decades and there has never been a problem. We just followed what we did in our other warehouses. Yet it is the compounding of these small “priming” types of mistakes that work together with a trigger event to cause major incidents, according to Fateen. Each one of these small mistakes primes your Pallet Rack System for catastrophic failure.

Priming Issue #1: Engineering Issues

Engineer of Pallet Racks
LARCs are the plans that detail your warehouse racking’s original engineering design. Your racks must not be altered from the LARCs or new LARCs must be created and approved by a qualified engineer.

Pallet rack systems are engineered for specific weight-bearing properties. The first small mistake that warehouse managers make is ignoring this fundamental fact, according to Fateen. The engineering of your entire racking system needs to be known and understood. Have your engineering plans readily available. These plans, in the industry, are called the Load Application and Rack Configuration Drawings, or LARCs for short. Study them. Know your rack-bearing capacities and every structural requirement down to the smallest detail.

Every little part of the racking system was put there for a reason by the engineer. Often warehouse managers will alter the racking system without consulting an engineer. Even a small change requires engineering approval. Your racking engineer will keep you from making a priming mistake. Fateen says that the warehouse racking gains strength from the collective interaction of all the parts of the system. The bracing, anchoring, struts, beams, and columns all work together to provide the collective strength to keep the whole system functioning. It is this collective “system” mindset that, when not understood, will have warehouse managers dismiss “small changes” or “small damages” as inconsequential. But these seemingly insignificant errors can significantly reduce the engineered strength of the entire system. 

Priming Issue #2: Alterations from Original Engineered Pallet Racking

Changing Racking Beam Height
Simple changes to your racking can alter its original engineering. For example, merely moving a beam position can alter the frame’s strength.

Additionally, alterations not in the original design can lead to racking failures and incidents. One issue that Fateen has seen over the years was moving racks to a new location. This is where you move to a new state, perhaps, and reassemble the racking like before. However, engineering is unique to each location. Fateen is a licensed engineer in all 50 states and knows from experience that seismic issues differ from location to location. Seismic data is now so specific requirements can be different within the same city or state. In addition, local building and fire codes vary, so you need to be mindful of this before merely moving racking to a new location. 

Simple alterations like moving beams change the engineering of a system. Fateen cautions that you need to keep the engineering of the entire system in mind, not just if the beam can handle the product weight. Moving the beam will change the system strength by changing the distance between beams. This new bay configuration can cause flexural deformations. Always consult your original plans, and if you need to deviate from those plans, even in small ways, consult an engineer. These unreviewed alterations could be part of the priming of your racking system for failure. 

Priming Issue #3: Loading Issues

Pallet Rack Loading Issues
Software can help prevent overloading racks beyond its capacity.

Most warehouse incidents, according to Fateen, have overloading or eccentric (unbalanced) loading as a priming error. The rack system usually has a high vertical weight-bearing capacity. But people don’t easily understand the horizontal stress that overloading and eccentric loading (uneven loading) cause. Your racking might not handle incorrect weights while swaying horizontally in seismic or impact events. For example, weight placed too high in the system is of particular concern, as this is harder to stabilize in the horizontal vectors. Your system might not even look stressed when you have an overloaded or unevenly loaded rack. But it is just waiting for the straw that broke the proverbial camel’s back. This is why improper loading is a priming error many warehouses fall into.

This mistake can be avoided by knowing your racking specifications and adhering to them strictly. Each bay should be clearly marked with a maximum weight sign. Modern warehouse software can keep you from overloading and eccentric loading errors by directing you to load by product weight and not by location only. Finally, using scales built into the forklift or a ground-based scale to weigh all pallets is also critical. All of this data must be tracked, and proper loading procedures adhered to. Improper loading can prime your racking system for failure.

Priming Issue #4: Collective Damages

Pallet Rack Damage Locations
It’s just a nick to a strut or a small ding in the column, but these small issues add up to a powder keg that could blow.

Racking systems seem amazingly resilient. This is due to the fact that they gain strength as a system. Fateen stresses that it is the design of the system that gives each bay and frame its strength. Each frame gains stiffness from the other frames it is joined to. Often when one minor dent in a column doesn’t seem to affect the rack performance at all. It seems to be holding the pallets and product weight just as it ever did, and so the small priming event is tolerated.

Collective damage on smaller pieces, like struts, seem small, so why worry and often, they are out of sight. Minor damage is frequently overlooked. Damage to anchor bolts and bolt shearing is seen as just a minor issue or having a rack that is slightly out of vertical or horizontal plumb. Minor dings and dents to columns seem unimportant. Yet collectively, many small priming errors can lead to preloading your racking system for warehouse collapse. These minor damages are often overlooked because the system seems to bear the vertical carrying weight of your pallets. The real issue to keep in mind is that failure happens when the racks are pushed into horizontal movement. So these collective priming mistakes of damage to the structure can reduce the capacity to withstand the horizontal forces from triggering events that you don’t see in day-to-day operations.

Routine pallet rack inspection and repair are essential. Mac Rak has a full line of pallet rack repair kits that can repair your rack with minimal downtime and expense.

Priming Issue #5: Racking out of plumb

A rack slightly out of vertical or horizontal plumb is a serious priming issue. A mere half-inch in ten feet of height is considered out of spec. Out of plumb, either side-to-side or forward or backward is dangerous. This misalignment is often overlooked when the system seems to bear the vertical carrying weight of your pallets. But remember that failure often happens when the racks are pushed into horizontal motion. These out-of-plumb issues can reduce the capacity to withstand the triggering events you don’t always experience in day-to-day operations. 

Priming Issue #6: Failure to Inspect

 A procedural issue that can prime your racking system for failure is not regularly inspecting your racking system. OSHA and RMI industry standards require regular inspections by professionals. These inspections can keep your system from being primed for failure, so don’t put off inspection and get in touch with a professional at Mac Rak. You can also use Mac Rak’s informal online inspection tool for preliminary inspections. It is available at MacRak.com/inspection. This tool will help you identify issues that a professional should address with a full inspection. 

Priming Issue #7: Fire Safety Neglect

Proper Flue for Pallet Racking
Neglecting fire codes can prevent sprinkler systems from reaching a fire lower in your racking system.

Fire can lead to massive warehouse destruction. Unfortunately, this too often happens one small error at a time. The most crucial issue is failing to install a proper sprinkler system. Not having sufficient flue space in double aisle designs so that fire suppression can reach all bays also contributes to fire problems. Storing flammable substances not permitted in your warehouse and hot weld repairs (which should never be done) where sparks fly and can ignite materials are all issues that can lead to massive warehouse failure. There are many tragic stories of fires in warehouses.

Priming Event #8 Failure to Protect Uprights

Forklift Racking Collapse
You need rack protection that uses unique anchor points that transfer impact forces to the floor rather than to the column.

The uprights are the racking system’s most vulnerable components and carry the most stress. Most uprights are not designed to handle a significant impact from a forklift. RMI recommends that you take steps to protect your uprights with pallet rack upright guards. Mac Rak manufactures a line of robust column guards made with solid structural steel components up to 1/2 of an inch thick steel sourced from the USA, assuring the highest quality steel to protect your racks. Additionally, Mac Rak protectors use multiple unique anchor points that transfer impacts to the floor rather than to your pallet rack uprights. Proper frame guarding must isolate the impact force away from the frame. All Mac Rak guards accomplish this by using separate anchor points. Failing to protect your columns can lead to minor priming events or major trigger events that cause forklift warehouse collapse.

Priming Issue #9 Flexural and Flexural-torsional deformation

Pallet Rack Flexural Torsion
Stress forces can bend columns and struts independent of impacts. This is Flexural Torson damage. Inspectors need to look for this type of damage carefully, as the strut or column can be compromised significantly.

Flexural deformation is when a column or beam bows out of its typical vertical shape. Flexural-torsional deformation is when the member is twisted by the stresses on it. It is a very dangerous state for a column or beam to be in, as the force is no longer compressing the column but moving horizontally. Interestingly, most structural pieces or racking systems fail in this manner rather than merely snapping. Before the failure of a column, forces will act on them to bow or twist.

The column can support massive weight on the down axis (y-axis). However, columns are easily bent, with far less force in the side-to-side axis (x-axis), when they have flexural deformations. This bending and twisting can occur from systemic failure, broken braces, eccentric loading, or bent or missing structural parts in other parts of the frame. Bending and twisting occur due to tiny strength differences in steel or inconsistencies in assembly. Eventually, bowing and twisting can lead to the column or beam snapping or hinging catastrophically. Flexural issues can happen slowly or suddenly. If you see this issue anywhere in your warehouse pallet racking, address it immediately. 

This video explains how flexural torsion works.

Priming Issue #10 Failure to Anchor

A forensic study of a collapsed warehouse by three engineers from Nelson Architectural Engineers found that two-thirds of the warehouse collapsed. It was determined that the collapsed racking was not anchored to the concrete floor. In contrast, the one-third that didn’t collapse was anchored. The lack of anchoring contributed significantly to racking shifting out-of-plumb and for flexural deformations to begin. Horizontal forces easily overwhelm the force of friction which is all that is holding the columns without anchors vertical. Over time more degradation of the racking occurs, priming the rack for failure. The forensic engineers determined that lack of anchoring can be a significant reason for systemic failure in their study.

PART 2: MAJOR TRIGGERING EVENTS

Accumulating many priming issues into your racking system can set you up for a progressive collapse. According to the Journal of Engineering Structures, a progressive collapse is “a sequential, domino-type failure. It is a situation where local failure of a primary structural component leads to the collapse of adjoining members which, in turn, lead to additional collapses.” A progressive collapse is merely waiting for a trigger event for a system failure to happen. The priming events degrade your system’s functionality to the point that it does not systemically function at its originally engineered level. According to Seizmic’s CEO, Sal Fateen, the system strength is often neglected. Your bays may hold the weight in them presently, but that doesn’t mean that your system can withstand a triggering event that will push it beyond its ability to stay vertical. Triggering events are impacts from forklifts, impacts from product, seismic events, resonance frequency stress, swaying, or natural disasters. Let’s look at each of these in greater detail.

Trigger Event #1: Forklift Warehouse Collapse from Impacts

Pallet Rack Forklift Impact
Forklift impacts are like a 9000lb wrecking ball. Racking is just not designed for these kinds of impacts.

Impacts from forklifts are the #1 trigger event that leads to racking system failure. According to Sal Fateen, you need to fundamentally understand that the weakest part of your system is the bottom of the column. Knock out the base of a column, and a frame can come down. We sometimes have difficulty conceptualizing the force involved in a forklift impact. The average forklift weighs about 9000 lbs, and the average speed is 3 miles per hour. We conceptualize that if a forklift bumped us, we’d fall down and likely get bruised badly. However, a rack frame is anchored to the ground and cannot move, so the frame’s metal (3-4 pounds per foot) is forced to absorb the entire force. Imagine dropping a 9000lb forklift onto one of your beams at a distance of 3 feet or swinging a 9000lb wrecking ball into one of your vertical frames. You start to understand the massive forces involved in a forklift impact.

Impacts at this speed with this massive weight directly at a column base are almost sure to take out the column, says Fateen. The size and scope of the failure incident will be determined by the priming events discussed above. Systems are designed to hold vertical weights and normal horizontal stresses. Forklift impacts can be massive horizontal force vectors that can quickly exceed the forces systems were engineered to withstand. Typical of this type of failure, the racks will fall towards the point of impact. Typically this collapse will fall into the aisle where the forklift and impact happen. This is dangerous for the driver and can cause a domino collapse of other aisles as the frames get pulled toward the triggering collapse. 

Forklift impacts can be reduced by using modern impact warning/prevention software like what is found in many modern cars that keep them in their lanes and warn you of potential collision hazards. Additionally, proper training will reduce driver errors.

Trigger Event #2: Seismic Event Triggers

Pallet Rack Forklift Impact
Seismic codes have become more detailed and can be different even in the same city due to local geographic issues. Each site requires a study to determine actual seismic vulnerability, according to Fateen.

Typically, your racking system is engineered to withstand the highest level of a seismic event in your area. This is true when the racking system is properly loaded and maintained to its original engineering specifications. However, with the accumulation of priming events, the racking system can be weakened and become vulnerable to earthquakes. Seismic events cause swaying forces either side-to-side or front-to-back. These forces push your system out of plumb, and the downward pressure begins to exert horizontal pressure beyond the engineering load capacity and the racking system.

According to Fateen, horizontal and forward-backward movement is where systemic failure often happens. Seismic swaying movements can push the capacity from vertical weight bearing to horizontal stress bearing beyond system capacity. Just because a rack stays upright doesn’t mean that a seismic triggering event will not cause the horizontal or forward-backward motion of just a few inches to cause warehouse collapse that has accumulated many priming events that weaken the entire racking system.

Sal Fateen, Seizmic Inc.

When horizontal force is exceeded in racking collapse videos, you see the typical “tip over” of the racking system. This type of trigger event can work in cooperation with priming events. If there are cumulative damages, errors in assembly, and overloading in the system, the ability of your racking system to survive a seismic event is significantly reduced. Your racking should be engineered to survive a maximum seismic event in your region at your typical loading and in optimal maintenance conditions. This means that the priming events are the catalyst that works with a seismic event to pull down your warehouse rack—a one-two punch with dire consequences.  

Trigger Event #3: Falling Product or Beam Collapse

Product falling can also cause an impact trigger. For example, if a pallet with heavy materials falls from an upper shelf, it can come down with great force and impact a column or beam. Likewise, a careless operator or a weak pallet can cause product to drop onto the racking system. A beam that is not properly connected or has rusted connection pins can also suddenly collapse and fall on the beams and bays below, triggering a racking collapse.

Trigger Event #4: Resonance Triggering Events

This video explains how Resonance frequency forces can amplify even a small impact to create significant damage.

Resonance triggering events can be caused by seismic events, collapse events, and blunt impacts. Resonance triggering events are a more complex scenario. The best example of this was the failure of the Tacoma Bridge failure. Tacoma Narrows Bridge Collapse (Color Video) Wind created a resonance frequency force that destroyed this bridge. The force of the wind wasn’t sufficient to blow the tons of steel down. However, the wind created a resonance frequency that the systemic engineering of the bridge could not dampen. In fact, according to these Siemens structural engineers, structures actually have a point where they amplify the resonance force. Natural Frequency, Resonance, and FRFs.

Pallet Rack Resonance Frequency Damage
Impact travels in waves down your racking system. These waves can hit an amplification point and take down your racking with destructive force.

This can be seen in some of the pallet rack collapse videos on the internet. You can see waves systematically down the racking system. While we cannot prove this was the destructive force that finally was the downfall of the rack, it certainly contributed. We see that the waveforms increase in amplitude and destructive force as they travel through the systems. This type of failure is characterized by a sudden massive failure of an entire aisle of rack. Generally, this results in a collapse straight down rather than to the side. Resonance effects can easily happen when liquid is stored in racks, as fluids transmit and amplify frequencies. Overloading can also contribute to resonance frequency damage, especially in higher bays. Once again, combining resonance triggers with smaller priming events gives you a perfect storm that can take down your racking system.

Trigger Event #5 Fire Triggering Events

Fire is not your typical structural engineering issue. It is, however, a systemic event that can destroy your warehouse. Fire is typically avoided if local fire safety codes are followed. But, unfortunately, when they are not followed, whole warehouses have been destroyed.

Trigger Event #6 Tornadoes and Hurricanes

Tornado Destruction of Warehouse
Tornados can’t always be stopped, so you need to have procedures in place to protect personnel when warnings are issued.

These events are typically beyond the engineering of your system to handle. This depends more on the structure of your building. In the case of severe weather, it is best to follow safety procedures for that event. Follow the directions of local officials and be aware of dangerous weather patterns. Have a plan to deal with tornadoes and hurricanes to assure the safety of your personnel. When forces of nature beyond your control strike your warehouse, you might not be able to prevent a warehouse disaster. Still, you can protect your staff from being in the warehouse, which is perilous in these types of extreme weather. For example, six people died recently in an Amazon warehouse collapse due to a tornado. This event tragically took place in Edwardsville, IL. CNBC reported that employees were never drilled, and some said they were unaware of the safety policies. While you might not prevent the loss of the warehouse, loss of life can and should be avoided with proper procedures put in place. 

CONCLUSION

Warehouse safety is a serious commitment. Every detail is essential to assuring the safety of your staff and the products and materials you handle. Warehouses are systems that are engineered as systems. Keeping all components functioning according to your original specification will prevent the priming events that make your warehouse racking system vulnerable. Likewise, avoiding the Trigger events can push a weakened system over the brink. It is essential to keep all of these details in mind at all times. This is a daunting task on top of all of your day-to-day demands. Mac Rak can be an essential ally in your efforts to keep all of your racking protected, inspected, and repaired. One call to Mac Rak could be the single most crucial step toward ensuring the safety of your racking system. Our experts are here to keep you safe and functioning efficiently so you can do your job of managing the warehouse. 

A WAREHOUSE MANAGER’S PATH TO WAREHOUSE COLLAPSE 

The schedule was fast and furious, and Tom was under immense pressure to keep the products flowing in and out of the warehouse as fast as possible. His stomach felt tense from the sheer volume of tasks on his plate. Worse, though, was this gnawing feeling that the dings and bangs that the racking was taking from the new drivers he had to hire to keep up were a ticking time bomb. He didn’t want to think about it. Then he got the call from the night shift manager he’d been dreading his whole career. There was an incident at the warehouse, we don’t know if two guys will survive, and umm, well, eight aisles of racking were wiped out. Tom dropped the phone and rushed to get dressed, feeling sick. His wife said, “What’s wrong?” but Tom couldn’t talk. He just said, “I have to go to work.” This is one phone call we at Mac Rak are dedicated to you never receiving. One call to Mac Rak will deploy our full force of inspectors, repair teams, and repair and protection products with minimal work on your part so you can focus on the frenetic pace of your warehouse job. We have your back so that the warehouse collapse never happens on your watch. Mac Rak will make sure every warehouse team member returns home to their family at the end of every shift.

Engineering Source References

Interview Source

Sal Fateen, SE, Licensed in all 50 states. CEO of Seizmic Engineering.

One of the leading warehouse racking engineers in the USA, with over 40+ years of experience in warehouse racking systems. Sal Fateen was interviewed by Mac Rak on May 31, 2022

Forensic Study

https://www.nelsonforensics.com/wp-content/uploads/2018/10/Collapse-of-Industrial-Storage-Racks.pdf

James P. Plantes, BS. 

Deepak Ahuja, M.S., P.E., MASCE

Ryan T. Chancey, Ph.D., PE, MASCE

Engineering Structures Journal 31(2009) 1460-1468 

Methods of restraining progressive collapse in rack structures

ALY et al.