can we still use knee brace as lateral structural resistance

[johndeng]

can we still use knee brace for lateral structural resistance? I remember knee brace is not allowed for lateral load with current code?

another question: for moment connections, top and bottom bolts can only be designed as slip critical bolts due to field condition? I was told they can't use standard holes for bearing type bolts.


Thanks

 

[spats]

I'm not sure where you get that knee braces cannot be used for lateral resistance. As far as I know, they're used all the time (If not, I'm in trouble). As far as slip critical bolts are concerned, my understanding is that if the kneee braces are subject to repeated load reversal (which they would be), then slip critical connections are required.

 

[fredPE]

Commentary to Chapter 11 in the Seismic Design Manual (page 6.1-170) talks about OMF Knee-Brace Systems, so they are allowed as long as you are in a region where OMF's are allowed. But OMF's are pretty significantly hindered in SDC's D and above, where the overall seismic dead load of the roof divided by the area of the roof has to be under 20 psf in ASCE 7-05 section 12.2.5.6 (and different requirements for 12.2.5.7).

 

[johndeng]

Thank you for quick response.
I do remember somewhere said knee brace is not allowed now, but I need confirmation here.

I am not using knee brace, but using Moment connections. I was told "without the oversized holes in the moment connection flange plates, there will be problems with the fit-up, requiring the erectors to enlarge the holes with a torch during erection of steel. so can only be slip critical connections." . I can't use standard holes, or even slotted holes. They have to be oversized holes, so slip critical connections. I need confirmation on this too.

 

[amec2004]

The effect of knee brace is just to make the joint where knee brace sitting to a moment connection

anchor bolt design per ACI 318-11 crane beam design

http://www.civilbay.com