Compression Flange Bracing????

[KarlT]

Let's say you have a 7" by 28" deep PSL beam spanning 30 ft. There are Pre-Engineered I-Joists bearing on top of the beam and the bottom of the beam is not currently restrained from lateral buckling.

Now let's say I determine the maximum allowable unbraced span length for the PSL beam for uplift, and decide I need to brace the bottom of the beam at the mid-span or the third points or whatever.

How do I determine how much force gets into these braces??? Does the bracing force depend on where you are along the beam (say max for a brace at mid-span) or is it assumed to be a constant force along the length of the beam.

 

[VoyageofDiscovery]

Hi KarlT,

The bracing force is a function of the stress in the supported member. If my memory is correct a PSL beam is a solid rectangular shape, so I am not familiar with supporting wood with ASD, but if you are supporting a flange then approx 1% of the flange force is required to support the flange at the chosen location.

HTH

Regards

VOD

 

[KarlT]

Ya the senior engineer in our office said the force is something like 2% of the total compression flange force as well...

 

[FSS]

Agree with the 2% range. Curious as to availability of a 28" deep PSL beam. Have seen 24" deep LVL beams but anything deeper had to be glulam. Also, are the joists floor or roof members? Just wondering how much net uplift you might have coming into your beam.

 

[VoyageofDiscovery]

I agree with the 2% for ASD, in the Canadian LSD for bridges it's 1% in addition to external loads on the bracing.

I should have been a bit more specific.

Regards

VOD