Bracing for Stability Question 1

[JD P.E.]

Per attached example you would use total load in all 3 bents to plug in to bracing stiffness equation even though both ends of structure are braced. The way I understand this is that each bracing member is designed for 2X the load it would theoretically see instead of 1X load (i.e. each braced bay would have it's tributary load).

Am I understanding correctly that this is basically just added safety factor for bracing design? Is this just standard practice for braced bays?

 

[canwesteng]

Looking at the partial snapshot here, it's hard to say exactly where the 2 comes from, but I believe it is from the stiffness required and not doubling the calculated load. Use the lateral load that is tributary to the frame.

 

[KootK]

My guess is that the structure shown in the sketch is really one module of a larger structure imagined to be constructed of several, repeating modules. Thus, the tributary load is indeed three bents (the load on one braced bent plus the load on two unbraced bents).

I agree, the presentation is confusing. Even the use of the term "bent" grates on me a bit. Bents are moment frames in my world.

 

[Tomfh]

Agree. Down with "bents".

 

[JD P.E.]

My guess is that the structure shown in the sketch is really one module of a larger structure imagined to be constructed of several, repeating modules.

Thanks KootK I think you are correct. The example says each brace bay must stabilize 3 bents which would make the numbers make sense if it was a continuing pattern.

I suppose if the structure shown was final, then the vertical load to be braced would be 750 kips (1500/2) for each braced bay + additional lateral trib forces involved?

 

[KootK]

I get 1000k per braced line but I think you've got the gist of it.