Allowable Deflection of a Cantilevered Beam

[CWIL]

I am struggling to remember how to determine the allowable delta max for a beam.

I am currently modeling the bending forces upon a piece of square tubing, and though developing delta max seems rather straight forward, I can not seem to remeber how to determine just how much deflection I am allowed in that beam.

Essentially... I have my delta max, but how do I know if that much deflection is OK in my design (failure due to Plastic Deformation)

Any input is appreciated

I have seen on another PF thread that 1" of deflection per every 250" of beam is an accepted approach. Is this accurate? What is the basis behind this estimation?

Thanks

 

[mohamadh95]

Well if the beam is supposed to act in an elastic way like steel you can easily use the double integration method. If it's made out of concrete it will be a bit more complicated. If you want further information just ask again and I will reply.

 

[mohamadh95]

Wait I think I got you wrong, you want to know the allowable deflection? You can find it in the construction codes like ACI.

 

[nvn]

Please see duplicate thread at thread 730175.

 

[alphy]

for reaching out for help on this topic. Determining the allowable deflection for a cantilevered beam can be a complex process, but there are some general guidelines that can help guide your analysis.

First, it is important to understand what causes deflection in a beam. Deflection occurs when a load is applied to a beam, causing it to bend or deform. This bending can be caused by external forces, such as weight or applied loads, or internal forces, such as stress or tension within the beam itself.

To determine the allowable deflection for a cantilevered beam, you will need to consider the material properties, size and shape of the beam, and the expected loads it will experience. This can be done through mathematical calculations or through computer modeling.

One common approach for determining allowable deflection is to use the deflection-to-span ratio, as mentioned in the thread you referenced. This ratio states that the maximum deflection should not exceed a certain percentage of the beam's span length. The specific percentage used can vary depending on the application and building codes, but a commonly used value is 1 inch of deflection per 250 inches of beam span.

This approach is based on the concept of serviceability, which refers to the ability of a structure to function properly and meet its intended purpose without causing discomfort to occupants or excessive wear and tear. Excessive deflection can lead to issues such as cracking, sagging, or failure of the beam, so it is important to ensure that the beam can withstand the expected loads without exceeding the allowable deflection.

In addition to the deflection-to-span ratio, there are other factors that can affect the allowable deflection of a beam, such as the type of material used, the shape and size of the beam, and the type of loading it will experience. It is always best to consult with building codes, engineering standards, and other resources to determine the most accurate and appropriate allowable deflection for your specific application.

I hope this information helps guide your analysis and decision-making process. As a scientist, it is important to always consider all factors and gather accurate data in order to make informed and effective decisions. Best of luck with your project!