How to laterally brace both flanges? 1

[SinaPeugeot]

I'm designing a SMF 12 story steel frame building. according to AISC, in SMF, both flanges of the beams must be laterally braced. can anyone PLZ send a detail about this lateral support.

I would appreciate any elp

 

[msquared48]

The top flange would be braced by connection to the floor or roof diaphragm, and the bottom flange would be braced with angle kickers from the bottom flanges of the steel purlins, unless the purlins were of the same depth as the SMF members.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[SinaPeugeot]

msquared48 tanx for the help,
i attached a picture of my floor system. as u can see the top flange is braced, but i didn't clearly understand how to brace the bottom flange. can u draw ur thoughts with Microsoft paint on the attachment picture plz?!

I really need this information.

 

[MiketheEngineer]

Run "kickers" from the purlins down to the large beam.

 

[sdz]

Something like this

http://www.draftsperson.net/index.php?title=Fly_Brace

 

[dcarr82775]

Like others said, run kickers from the bottom of the girder to the beams or slab. But remember to design the kickers for the required bracing load and check the other members for their ability to support the loads.

 

[tclat]

What would one do if the floor system is a composite steel deck?

If both the beam flanges need to be braced then it would seem that the flanges for the column also need to be braced. If so, how do you do this if you have a glass curtain wall.

If not what is the rationale for bracing both flanges in the beams and not in the columns.

 

[SinaPeugeot]

yes dcarr82775,

I've checked it and in my country they are designing the kickers for the 5% of the flange compressive strength,

Tanx for the help.

 

[jike]

tclat:

Beams are usually deep and narrow, which require bracing in the compression zones to maintain a higher allowable stress level.

Columns are often approximately square, which allows it to span longer distances without significant reduction in allowable stress. Where columns are deep and narrow, they often need bracing similar to beams.

 

[SinaPeugeot]

tclat:

Also, the beams connecting to a column at the story levels will usually insure the required bracing.