Local column deflexion

[dan03]

Hello

Can you tell me what is your deflexion criteria to calculate the mid deflexion of a steel column depending of the exterior finish (like dryvit, concrete pannel, brick...) or the interior finish like gypsum? For these type of finishes, is L/240 acceptable?

When the column is longer than 20 feet, this criteria become very significant.

Thanks.

 

[UcfSE]

You will have to find that in the governing building code under which you work. Frequently we use span/240 or span/360 unless it is brick. Flexible finishes might be permitted more deflection than that. Brick supports are often limited to span/600. Again, it is up to the building code to set a maximum and your judgment if you decide to use a stricter limit.

 

[dan03]

Hi UcfSe

Thanks for these informations. Here I use the canadian National Building Code (NBC). For the wall, the only specification is the use of L/180 for the wood structures and there is no specification for the steel and concrete structures.

So what is the specifications for your building code?

Thanks a lot

 

[dan03]

Is anybody can tell me what is your specifications in your building code for the wind load??

 

[UcfSE]

Those I posted are for wind load. Roof allowable differ typically from wall allowables. Allowable deflection is not dependent on what the element is but rather what the element is supporting. The purpose of limiting deflection is to prevent damage to non-structural cladding such as plaster, gypsum board or brick. The limitations are recommended based on historical performance data or experimental values. When a support such as a wall stud deflects the cladding deflects with it and therefore feels some strain. Limiting the deflection limits the strain in the cladding, hopefully to an amount less than that which causes damage. Look in the structural loading chapter of your code for these limits, that is where they are found in several codes here in the US.

 

[dan03]

This is exactly why I posted that. In our code, there is no specification for the wall deflexion in steel structure or concrete structures. For the roofs, we found limits for differents cases.

But for the walls, the limits is subject to engineer judgment. This is why I would have your specifications ou experiences, it's to have more documentation for further discussion.

Thanks