Beam retrofit

[Leftwow]

Good Afternoon,

I am currently working on a modification to reduce the deflection on an 18' long beam. The load on the beam will be about 25 kips. My superior wants the to reinforce the beam in order to reduce the deflection due to operational loadings. I am thinking of unbolting the existing beam and replacing it. What are some ways of reinforcing a beam for deflection you guys have used in the past. Also, please see attached.

 

[KootK]

That's a tiny little beam. You could bolt a pair of stocky 8" channels to the web and increase the stiffness substantially.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[jayrod12]

That's a tiny little beam. You could bolt a pair of stocky 8" channels to the web and increase the stiffness substantially.

That's precisely why I asked the level of increase required. If he needs a ridiculously substantial increase, then I don't think there's a better option but remove and replace. If minor, there's likely a few option without welding that we could come up with.

 

[Leftwow]

I would like to reduce the deflection by about 50%.

2 questions:

1 - How are you guys describing stiffness (units, thoughts)...

2 - How would the orientation of the C-Channel likely be?

- back of channel to web of IPE
- flange of channel to web of IPE

 

[gtaw]

Consider welding additional plates to the underside of both the top flange and the bottom flange of the existing WF beam. Remember to bevel the inside corner of the top plates to clear the radius of the beam web/flange.

The welds do not need to be continuous. Intermittent fillets are usually sufficient. One must calculate how much and what size fillets are needed.


Best regards - Al

 

[KootK]

Stiffness is EI. So MPa x mm^4. I'd put the channels such that their webs were in contact with the wide flange web. You might need shims in between to clear the fillets between the beam web and flanges.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[jayrod12]

So you want to double your Moment of Inertia?

Is remove and replace really not an option? That's a fairly large increase required. It's also surprising that you need that stiff of a beam, but strength and vibration are non-issues.

 

[rb1957]

increasing I (by adding to the caps) is maybe only part of the solution. If the original beam is "tiny" then maybe then web needs some help too ?

another day in paradise, or is paradise one day closer ?

 

[canwesteng]

If steel is cheap and labour is expensive, install a new beam directly below this beam for it to bear on. Only bolt it to transfer shear at the ends - it won't function as a composite beam, so stiffness is simply the sum of the stiffness of the two beams. An inefficient but sometimes elegant solution.

 

[Leftwow]

We are going to go with the C channels for the added lateral resistance along the beam.

 

[vhengr]

Is there any possibility to bring fixity at ends to the said beam by providing Top & Bottom Flange Splice plates?
May be you find it a economical way to reduce deflection. (Another Whacky alternative...)

Note: The Supporting Beams's capacity need to be validated for these addition moments which got transferred to it due to moment connections.

Cheers! -VH

 

[Leftwow]

Yea there is but it's not a frame beam it's just a support beam so there is no column present in that location. The problem comes in where on beam's deflection is nil and the other beams deflection is an inch. We the other beam is fixed while the concerning beam is pinned.