Are Moment Frame, Lateral Bracing or X-bracing; "Structrual" 1

[RPCFPPM]

My current project Structural notes state: The steel structure, or portions thereof has been designed as a non-moment resisting frame relying on the floor and roof decks and braced frames for lateral stability.

The cities special inspector claims that the brace frames are a structural member. My understand is that such questions can only be determined by a structural engineer. Thus, an RFI was submitted to the Arch/S.E. firm (fTC&h). There lazy response was the braces carry a lateral gravity load, thus, they are primary because of the wording 'gravity'. I can find no reference to a "Lateral Load Bracing".

My opinon is this term was made up at the same time the Architect was deciding on what to order with his: I don't give a damn sandwhich.

IBC Code (Table 601) states: "The structural frame shall be considered to be the columns and the girders, beams, trusses and spandrels having direct connections to the columns and bracing members designed to carry gravity loads. The members of floor or rooof panels which have no connection to the columns shall be considered secondary members and not a part of the structural frame."

My contention is the moment frames, lateral bracing, etc. are not a Structural Member, by definition. Perhaps they play a role in load bearing in a secondary compacity, but the primary role is for either; sismic, wind, bracing, etc.

The City Special Inspector is equally oblivious to reality. Am I correct? or are these types of members truly structarl, per this code or UBC for that matter.

Please help or provide a directional arrow, thank you.


David B
RPC
P.M.

 

[JAE]

Braces are indeed part of the structural frame. AISC Code of Standard Practice, section 2.0, indicates that bracing is "Structural Steel".

As far as the IBC Table 601 goes, in defining "structural frame" for fire-resistance, you have to realize that all braces are primarily designed to take lateral forces from wind, seismic or earth loads. However, any frame is not specifically/perfectly plumb, and under gravity only conditions, there are both primary and secondary lateral effects that the bracing resists. So the response that the bracing takes gravity loads is technically correct.

Why Table 601 doesn't specifically mention bracing is beyond me.

 

[BSE05]

How many times have you been "sucked" (for safety sake)into designing miscellaneous iron for all those items that architects project or hang off the frame? Ouch.

 

[EddyC]

RPCFPPM,

I'm not sure what your problem is exactly. Is it one of cost? Is it one of safety? Could you amplify please?

 

[EddyC]

I've seen several buildings under construction that had X bracing. The bracing on all of them was fireproofed.

 

[RPCFPPM]

Thank you to all: I appreciate the input. No more discussion is needed.

 

[civilguy98418]

Hmmm.

Is it me or is there actually such a thing as a lateral gravity load?

 

[csd72]

Some codes specify a minimum lateral resistance of 1 or 2% of the gravity loads to allow for out of plumb e.t.c. Maybe this is what it refers to.

 

[rook1]

civilguy98418, i think you are right... could somebody clarify more on the "lateral gravity load"?

 

[whyun]

Could it have meant seismic dead load?

Off tangent, lateral gravity load may be observed in roof davits, depending on the placement.