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The primary trigger event that leads to racking system failure is impacts from forklifts. The bottom of the column is the weakest part of the system. Knocking out the base of a column can cause the entire frame to collapse. We often struggle to comprehend the force involved in forklift impacts. Even though an average forklift weighs 4 tons and moves at 5 kph, we tend to imagine that if a forklift hit us, we would likely get bruised badly and fall down. However, a rack frame is anchored to the ground and cannot move, meaning that the entire force is absorbed by the metal frame. Dropping a 4tons of forklift 1m away from one of your beams or swinging a 4 ton wrecking ball into one of your vertical frames helps illustrate the enormous forces at play.

According to Fateen, impacts at this speed and weight directly at the column's base are highly likely to take out the column. The size and scope of the failure will depend on the priming events discussed above. Systems are designed to hold vertical weight and normal horizontal stresses. Forklift impacts can be massive horizontal force vectors that can quickly exceed the forces systems were engineered to withstand. Typically, the racks will fall towards the point of impact, collapsing into the aisle where the forklift and impact occurred. This can be hazardous for the driver and may cause a domino effect of other aisles collapsing as frames get pulled towards the triggering collapse.

Modern impact warning/prevention software, similar to what is found in many modern cars, can reduce forklift impacts. This software can keep forklifts in their lanes and warn drivers of potential collision hazards. Proper training can also reduce driver errors.

Normally, your racking system is designed to withstand the strongest seismic activity that can occur in your region, given that the system is designed for the seismic standards of the location installed and that its loaded and maintained according to its original engineering standards. Nonetheless, when a series of priming issues accumulate, the racking system can be compromised and become susceptible to seismic events. Earthquakes generate swaying forces that move the system laterally or longitudinally, causing it to lose its vertical alignment. The resulting downward force places excessive horizontal pressure on the racking system beyond its engineered load capacity.

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When the racking system collapses due to excessive horizontal force, it typically topples over as seen in collapse videos. Such trigger events can be compounded by the accumulation of priming events such as structural damages, assembly errors, and overloading. These factors significantly reduce the ability of the racking system to withstand a seismic event. Ideally, the racking system should be engineered to survive the most severe seismic activity in the area under typical loading conditions and with optimal maintenance. Therefore, the priming events act as a catalyst that, in conjunction with a seismic event, can bring down the warehouse racking system.

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SPIMA have extensive experience in seismic pallet racking and can assist you in designing according to your requirements.

A collapse trigger can also be caused by falling products. In the event that a pallet containing heavy materials falls from an upper shelf and comes crashing down with significant force onto a column or beam, this too can cause the start of a collapse.

 

Similarly, a product may fall into the racking system due to the carelessness of an operator or the use of a weak pallet. If a beam is not appropriately connected or has rusted connection pins, it can suddenly collapse and fall onto the beams and bays below, leading to a racking collapse.