Overstrength factor for hat truss? 2

[milkshakelake]

Do I need to consider hat truss with overstrength factor? Sketch below. This one is a vierendeel truss. I'm not sure what to make of it, if it creates soft story/vertical irregularity or not. I'm inclined to think that it doesn't, because the stiffness of the lateral system is a collective unit using the entire column on all stories.

 

[KootK]

The hat truss basically functions as an outrigger system, correct?

I've got a copy of this document: CTBUH Outriggers. It's been a while but, if I recall correctly, they make a pretty good case for not applying overstrenght to such systems. I'll try to find some time to dig into that if you want me to.

 

[milkshakelake]

@KootK Thanks so much! The document answers my concerns fully, and it's pretty much what I thought. It definitely helps to have it in a publication.

For anyone coming across this a hundred years in the future, after I have expired (hopefully not) and my outriggers are still functional, this is the answer from the publication:

 

[HTURKAK]

English is my first language . However my interpretation is , Vertical Structural Irregularities Type 3 exists ( Table 12.3-2 )

Copy and paste of the same ; 3. In-Plane Discontinuity in Vertical Lateral Force-Resisting Element Irregularity is defined to exist where there
is an in-plane offset of a vertical seismic force-resisting element resulting in overturning demands on supporting structural elements .

I understand the outermost left and right columns supporting the HAT TRUSS should be designed with load cases that include the overstrength factor .

I have marked the subject columns with dark blue .

My opinion .

 

[milkshakelake]

Hello @HTURKAK , thank you for your opinion. I believe that there is no in-plane discontinuity because the overturning demand is subject to a lateral system that has equal stiffness on all floors. The outrigger system uses the column as part of its stiffness, and it is not more stiff at the top than at the bottom. The following diagram from "Outrigger Design for High-Rise Buildings" shows this visually in my opinion. A soft story from vertical in-plane discontinuity would show a lot of drift in the lower stories, and significantly less drift at the outrigger level.