Non-building Structures Similar to Buildings
Non-building Structures Similar to Buildings
(OP)
I have a free standing, 4 column concentric braced frame stair access tower in a seismic design category D zone.
It can be classified per ASCE 7-05 table 15.4-1 as an ordinary concentrically braced frame, whereby you have to either design it as a building or use a low R value of 1.5. As far as I can tell it would be subject to the redundancy requirements in chapter 12 no matter what the R value.
Or it can be classified per table 15.4-2 as a freestanding trussed tower with R=3 and minimal detailing requirements.
What defines a non-building structure similar to a building?
It can be classified per ASCE 7-05 table 15.4-1 as an ordinary concentrically braced frame, whereby you have to either design it as a building or use a low R value of 1.5. As far as I can tell it would be subject to the redundancy requirements in chapter 12 no matter what the R value.
Or it can be classified per table 15.4-2 as a freestanding trussed tower with R=3 and minimal detailing requirements.
What defines a non-building structure similar to a building?






RE: Non-building Structures Similar to Buildings
RE: Non-building Structures Similar to Buildings
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Non-building Structures Similar to Buildings
Since you are using R=1.5 for the OCBF, it sounds like it is really tall, otherwise you'd be using the R = 3.25.
Bummer.
Trussed tower seems appropriate if it's quite tall, and without diaphragms (multi-brace up the height = truss).
R=3 for TT... See 15.7.3: I would still keep the principals of seismic design (ductility) in mind when designing these connections. It's better to have ductility with forces of a low R, than no ductility with forces of a high R.
Basically, to slow down a building in an earthquake, something has to yield. With minimal details, that weak link is failure (possible brittle failure) of your connections. Hence you are forced to have the higher forces (strength development) of a low R.
Also, closely examine where you need to use the Omega factor in 15.7.3, and elsewhere.
So, a little care in detailing would be important, and not that crazy to do, if it as repetitive as I imagine.
Best wishes!