how to deal with holes in static analysis of beam in bending?

[Tweedclassic]

I am trying to determine maximum stress in a beam in bending with multiple holes on the side of it, using (stress = Mc/I). The maximum moment occurs in the middle of a hole. what I and c values do I use? do I use the cross sectional area minus the hole diameter for the I and c ? or pretend the hole doesn't exist for the stress calculations? do the holes next to it need to be taken into consideration? for static analysis should I ever consider stress concentration factors? this is a ductile material.

Thanks

Robert

 

[msquared48]

Consider the modified I and C values. Place the holes at the centerline of the beam.

What is the diameter of the holes, location along the beam, and the depth of the beam?

Mike McCann
MMC Engineering

 

[desertfox]

Hi

Any chance of a sketch, if the holes are in the side of the beam I cannot see how maximum stress would be at the centre of the hole.
Further I'm not sue how accurate you want to be but I would workout the stress at different points ie max and min 'I' values then apply some stress concentration factor to account for the holes.

desertfox

 

[TLHS]

I'm not sure what 'the side of it' actually is in this case, but you likely want to refer to AISC Design Guide 2, Design of Steel and Composite Beams with Web Openings

http://www.aisc.org/store/p-1569-design-guide-2-design-of-steel-and-composite-beams.aspx

 

[BAretired]

Is this a steel beam, wood beam or other? Provide a sketch showing hole sizes and locations.

BA

 

[briancpotter]

The design guide can also be found online here:

http://portales.puj.edu.co/wjfajard...eel And Composite Beams With Web Openings.pdf

Brian C Potter, PE
Simple Supports - The history and practice of structural engineering.
ConstructionPic - Send annotated jobsite photos.

 

[rb1957]

you can account for the holes by having spaces in your cross-section (so I will be a little smaller).

"c" would be the distance to the edge of the hole (less than the edge of the beam, yes?, so probably not critical).

you could include stress concentration if you want to be (IMO) hyper-conservative.

if you're feeling nervous about these holes, you could do a fatigue calc with stress concentration effects and typical service loads (as opposed to extreme static design loads).

you may need to think about the effect of holes on the allowables ... a web with an unreinforced/unflanged lightening hole has a reduced shear allowable.

Quando Omni Flunkus Moritati