Warehouse  collapse and how to prevent it

The resilience of racking systems is impressive due to their ability to gain strength as an entire unit. The design of the system gives each bay and frame its durability, with stiffness increasing through interconnection to other frames. Even when an upright sustains minor damage, the rack's performance is not typically affected and is still capable of supporting pallets and product weight.

Unfortunately, damage to smaller components like braces and anchor bolts or small dents to uprights is often overlooked because it may seem insignificant or out of sight. However, these seemingly minor issues can accumulate over time and lead to catastrophic failure if the system is pushed into horizontal movement. It is crucial to prioritize routine pallet rack inspection and repair to prevent such scenarios. 

Many of the small knocks, specifically on uprights which the most critical component, can be almost eliminated by providing upright protection throughout the whole system. 

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Many companies disregard this and only focus on the rack end barriers, however upright protection is equally important. Dents as shown in the image above will not be present with proper upright guards.

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Spima can supply both polymer (A-SAFE) and metal rack protection.

While racking is considered usually as a mere commodity (a heap of metal), businesses are often lured to buy cheaper second hand racks from resellers, or from companies that have closed down to name but a few. While this is a cost saver, it does pose a large threat as there is no way of knowing what the internal condition of the steel is (could have been subjected to corrosion ans hence weakened), it could have had minor dents that are not clearly visible, or may not have been assembled correctly. 

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If the rack has been present at the old establishment for many years without knowing how the operators have been using it, hence its physical condition is completely unknown, and if the original engineering plans that the system was assembled with and outlined its rated capacity do not exist, you are jeopardizing your business and staff unneccessarily - if you have a rack failure you will be 100% liable.

Overloading or unbalanced loading is a common priming error that may lead to a future incident. While rack systems typically have a high vertical weight-bearing capacity, people often overlook the horizontal stress caused by overloading or uneven loading. The racking system may not be able to handle incorrect weights while swaying horizontally during seismic or impact events. For instance, placing weight too high in the system can be especially problematic as it is harder to stabilize in the horizontal vectors. Even when an overloaded or unevenly loaded rack does not appear stressed, it may be just one step away from a catastrophic failure. Improper loading is thus a priming error that many warehouses fall victim to.

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To avoid this mistake, it's crucial to know your racking specifications and to follow them strictly. Each bay should be clearly marked with a maximum weight sign. Modern WMS software can help prevent overloading and eccentric loading errors by directing you to load products based on weight, not just location. Additionally, using scales built into the forklift or a ground-based scale to weigh all pallets is critical. All of this data should be tracked, and proper loading procedures followed. Failure to load properly can initiate your racking system for a major disaster.

Modifications that are not part of the original design can result in racking failures and accidents.

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Minor modifications, such as moving beams (especially the first beam level), can have a significant impact on a system's allowed load and may weaken it substantially. It is crucial to consider the design of the entire system, not just whether the beam can handle the weight of the product. Always refer to the original plans and, if necessary to deviate from them, always get the manufacturer's approval in writing. These unreviewed changes may contribute to the priming of your racking system for failure.

Any rack parts that have been subjected to moisture or corrossive substances will no doubt have an effect on the component's ability to hold its rated load. Corroded parts are considerably weakened and hence can easily break if a load is accidentally placed onto it with more force than normal, whereas a normal component would probably take the hit.

This is an issue commonly overlooked as pallets are usually unloaded from containers and placed onto racks immediately. Exporters are not bothered to use good quality pallets for exports hence the destination warehouse will have to either mount it on to a proper sturdy pallet, or risk breakage inside the rack resulting in falling goods.

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Goods on pallets are often in excess of 700 kgs so a fall will have a significant impact on the structure. In the event of pallets breaking or failing, the items stored on them or the entire load could slide off the pallet, striking whatever surface is beneath. If a pallet breaks while being loaded or unloaded from the rack system, the rack itself may be subjected to the force of thousands of kN of falling material.

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When items or loaded pallets land on a shelf, some of the horizontal energy can transfer to the rack, which can create hazardous conditions. The swaying of pallet racks can put excessive stress on weaker connecting parts, such as the joints where the beams and frames meet or the struts, potentially causing damage. If a rack is already close to its maximum load capacity or has unrepaired damage, it can easily buckle under extreme pressure.

A rack slightly out of vertical or horizontal plumb is a serious starter issue. A mere 1 cm for 3m 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. 

The absence of anchoring or even part anchoring can lead to the racking becoming unstable and torsional deformations beginning to occur, causing the columns without anchors to shift out-of-plumb. As a result, the horizontal forces can easily overpower the force of friction of the base plate that holds the uprights in place, causing the collapse. The lack of anchoring can also contribute to the gradual degradation of the racking, making it more susceptible to failure. Based on existing rack collapses, forensic engineers have concluded that the absence of anchoring can lead to systemic failure in racking structures.

When an upright or beam twists and deviates from its normal vertical or horizontal position, it is referred to as torsional deformation. These conditions are hazardous for columns or beams since the force applied is no longer compressive but moves in a horizontal direction. Prior to collapsing, columns or beams will exhibit signs of bowing or twisting due to the forces acting on them.

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While an upright can bear tremendous weight vertically along its down axis , it is susceptible to bending with much less force when applied in the side axis (when torsional deformations occur). Such deformations may arise from various factors, including systemic small impacts, broken braces, eccentric loading, or bent or missing structural components elsewhere in the frame. Over time, these torsional issues can worsen, eventually causing the column or beam to snap or fail catastrophically. These problems may occur slowly or abruptly, and immediate attention is necessary if such issues are detected in warehouse pallet racking.