Web Holes

[LIGWY]

I am currenly working on a project and there is a W36x135 and our client would like to place holes in the Web. They would like to place 3-3" Diameter holes in 4 different locations along the beam. The beam is 32' long. The first set of holes would be at 4' on each end and the other sets placed 8' apart.

I am looking for a good revference with examples. All I can find is the ASCE Task Committe (7.33, 7.34) should serve as a basic guid but I have not been able to locate this information.

 

[COEngineeer]

How would you put 3'3 on a 3' deep beam?

 

[COEngineeer]

oh maybe you meant 3 3/16", my bad. Well, draw the moment diagram and shear. You will have reduced Zx at the 4 locations and you will have the Mx and Sx at 4 locations.

 

[hokie66]

He said he had 4 sets of holes, each 3 holes at 3" round, and the first set is 4' from the end of the beam.

In this case, the holes are no problem. Space them on about 9" centres, leaving 6" of meat between the holes, and at middepth.

For larger holes, there are probably already threads dealing with them.

COEngineer, lost your glasses?

 

[mrengineer]

See AISC Design Guide 2 "Steel and Composite Beams with Web Openings"

 

[csd72]

If it is only 3" diameter and it is in the middle third of the web, then I would just check the stresses of the reduced section.

They do these type of holes all the time and often dont tell the engineer. The AISC design guide is really applicable for larger holes.

 

[271828]

I agree with some of the others who said they wouldn't really worry about holes that size. The beam won't even know they're there.

Just to be complete though, this isn't something like a transfer girder with a 900 kip reaction landing right on top of one of these holes, right?

 

[UcfSE]

Use the design guide that mrengineer referenced. It is pretty reasonable about calculating the effects of web penetrations. RAMSBEAM will calculate the effects of the holes for you if you have access to it.

Like others have said, I doubt a hole like that will have a large effect but it may be significant if you are already near capacity. It's worth checking imo.

 

[COEngineeer]

I always put (3) to signify how many. 3-3" is asking for mistakes. I just need glasses to drive lol.

 

[LIGWY]

Hokie66 You are correct on the size and the layout of the holes.

This beam does not have a 900 kip load on the beam anywhere.

My concern was not necessarily one hole but there would be a total of 12 holes in the beam.

 

[UcfSE]

With the design guide you'll be able to check not just the holes but their size and spacing as well. This will allow you to put some vertical and horizontal tolerance on the hole location in your design and make it better for the field personnel.

 

[vmirat]

"Roark's Formulas for Stress and Strain" has tables for stress concentraction factors for things like this.

 

[jetmaker]

Another reference is ESDU if you have access to their servers. They provide additonal information on penetrations and discuss reinforcing methods if so required.

 

[csd72]

vmirat,

If you have it in the middle third, the stress concentration factors actually work in your favor. The elastic stress is only 1/3 of the maximum and the concentration factor wont be more than 3. The result is just better utilisation of the steel above and below the hole.

regards

csd