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Deflection is the amount an object bends from its original position.  Deflection can be seen anywhere a load is being supported.  There is more than one formula associated with deflection depending on the type of loading and bracing, so be sure to select the appropriate formulae for your application.

In the image below, a beam without any load will rest in a level state, illustrated by the black line.  When a load is applied to the beam the beam will bend, illustrated by the orange line.  The distance from the beams original position to its loaded (bent) position is the deflection.

When the beam is loaded and deflection exists, there are a lot of additional loading conditions being applied.  Some of these loading conditions may be viewed as negligible, however it is a designer’s responsibility to recognize that a combination of negligible loads may add up to an amount significant enough to cause a failure.

From the image above, the loading on the supporting columns (vertical members) changes from a pure Axial (Vertical) load to a combined load including lateral (Side) loads.  If the designer is focused on the static design (loads applied along the x axis only) the product may not meet the safety requirements outlined by several standards.  A good designer should take into consideration the effects of being dynamically loaded.  Attention to dynamic loading will be reflected in the durability, quality and ultimately the safety of the product.

We can predict the theoretical deflection amounts through manual calculations and through modeling software programs such as Solidworks, Catia or Inventor to name a few.  With the theoretical or measuring the actual deflection, we can compare the amount with a published set of standards to justify the product is designed based on sound engineering principles and is not likely to fail under normal circumstances.

A deflection test could be taken later as well to evaluate the effects of repeated use over a period of time.  The repeated loading applied to a beam is referred to as fatigue loading and can cause damage leading to catastrophic failure.  Maintaining a record of deflection measured each year may highlight a products failure before it happens, potentially saving a life.

To have a properly designed piece of lifting or structural storage equipment contact Jason Harnest, Director of Engineering at jharnest@carneyfabricating.com to get the optimal design based on strength and deflection.

 

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