Beam Deflection

[morinp]

How to Eliminate Beam Deflection?

 

[IDS]

The only methods that come to mind immediately are to use infinitely stiff materials, or to apply zero load.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[morinp]

the beam was already installed together with the load. there is a calculation provided to us, but it exceeded the allowable deflection.any action that we can do to minimize or to correct the excessive deflection.? may we use a tension wire or a brace to eliminate the deflection?? it is fixed on both ends, and there is no way that we can jack it up on the center, i really appreciate your help.. thanks .

 

[KootK]

Look into external post-tensioning: [link 4.bp.blogspot.com/_Q2L1ONLb7Hc/TJBIcJIdw1I/AAAAAAAAF04/VX3yEaKqRfI/s1600/13.JPG]Link[/url]

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.

 

[morinp]

Thank you for your response..

 

[IDS]

OK, that gives us a better idea of what the problem is.

External pre-stressing is probably the best bet. Is temporary propping possible? If so jacking up and application of external FRP reinforcement might be an alternative.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[CELinOttawa]

In steel I have successfully used flame cambering... Not for the faint of heart, nor the inexperienced.

 

[BAretired]

In steel I have successfully used flame cambering... Not for the faint of heart, nor the inexperienced.

and not for a loaded beam.

BA

 

[msquared48]

1. Replace the beam with one of the same material with a larger moment of inertia
2. Add another beam to the side or transverse to it
3. Use a different material with a higher elasticity
4. Reduce the load
5. Add an intermediate column to support the existing beam
6. Install antigravity generators


Mike McCann, PE, SE (WA)

 

[JStephen]

Can you remove it to modify it? If so, you can add side plates, plates on web or flanges, etc. If you welded that stuff on the loaded beam, you'd just have a bigger overdeflected beam.

Consider looking into that deflection criteria carefully. Whether that will help depends on the application and the customer. But, I have seen maximum deflections specified where there was absolutely no reason to specify a maximum deflection.

If you can remove the beam, there are companies that can camber a fairly large beam- that would depend on your schedule, too.

Is the problem deflection a measured deflection or the calculated deflection? If the latter, some additional consideration of end conditions, etc. may help (or just as likely, hurt!)

 

[CELinOttawa]

and not for a loaded beam

Good advice, but not an absolute. If you can get the load down to close to dead load only, and have propping involved, you *can* and I *have* undertaken flame cambering on a loaded beam.

It is, of course, a damn good way to cause a progressive collapse, a localized collapse, or all sorts of other nasty unintended results should anything go wrong...

DO NOT undertake flame cambering for the first time without knowledgeable support as well as a an, ideally old and grizzled, steeley.