Cantilever Column Systems - R Value / Detailing
Cantilever Column Systems - R Value / Detailing
(OP)
I have a question regarding the "R" value for cantilever column systems in ASCE7-05 (well, several, actually). Section G of the table gives values for seven different types of systems.
The way it is phrased is this: "Cantilevered column systems detailed to conform to the requirements for:" Then lists:
1. Special steel moment frames
2. Intermediate steel moment frames
Etc.
How does a cantilever column conform to details for a special moment frame? By definition, it does not take moment at the top; therefore, the FEMA 350 / AISC requirements are not applicable. Do you just check the column size restrictions? If so, what about tube steel / HSS type columns?
What is the difference in detailing requirements between SMF and OMF with respect to steel cantilever columns?
What is a "timber frame" and how do I ensure detailing conformance?
Since the base plate is the only connection to take moment, perhaps that is what should be detailing according to moment frame requirements. What is the difference between, say, a SMF base plate and an OMF base plate?
Basically, if a plan checker asked me why I chose a particular r value, how can I justify that decision?
The way it is phrased is this: "Cantilevered column systems detailed to conform to the requirements for:" Then lists:
1. Special steel moment frames
2. Intermediate steel moment frames
Etc.
How does a cantilever column conform to details for a special moment frame? By definition, it does not take moment at the top; therefore, the FEMA 350 / AISC requirements are not applicable. Do you just check the column size restrictions? If so, what about tube steel / HSS type columns?
What is the difference in detailing requirements between SMF and OMF with respect to steel cantilever columns?
What is a "timber frame" and how do I ensure detailing conformance?
Since the base plate is the only connection to take moment, perhaps that is what should be detailing according to moment frame requirements. What is the difference between, say, a SMF base plate and an OMF base plate?
Basically, if a plan checker asked me why I chose a particular r value, how can I justify that decision?
-AC






RE: Cantilever Column Systems - R Value / Detailing
Does it perhaps relate to the requirements of what shapes are allowable to use for the columns? For example, you could use HSS shapes for Ordinary, but might be limited to compact flange WF for Special?
I am eager to hear what others have to say about this.
(p.s. my project is under California CBC 2007, DSA; there may be different local requirements, for example in Los Angeles.)
RE: Cantilever Column Systems - R Value / Detailing
Personally, I just put the dog-bone in the column and call it a SMF. ;)
RE: Cantilever Column Systems - R Value / Detailing
I think this is an irresponsible attitude. If anything, if you are going to throw a dart, you should pick the lowest possible R value (1.25, in this case).
I am surprised no one has any experience with this issue. No one has designed a cantilever column in the 4 years since ASCE 7-05 was published? Really?
-AC
RE: Cantilever Column Systems - R Value / Detailing
RE: Cantilever Column Systems - R Value / Detailing
Great! What publication states this premise?
-AC
RE: Cantilever Column Systems - R Value / Detailing
RE: Cantilever Column Systems - R Value / Detailing
On a side note, your attitude, tone, and sarcasm dripping in your responses is irreverent and is not making you any friends. If I were you, I'd be more polite if you want more responses.
Obviously you wouldn't put a dogbone in a cantilevered column. Sandman was joking.