One Story Biaxial Ordinary Moment Frames Options Per AISC 341
One Story Biaxial Ordinary Moment Frames Options Per AISC 341
(OP)
What are good options for shapes & FR moment connections (if any) for a one story biaxial Ordinary Moment Frame designed in accordance with AISC 341? I am assuming the structure size does not warrant the price tag of utilizing proprietary connections. For the sake of discussion consider a one story frame with columns in a square arrangement (15'x 15'x 15'), structure is in a SDC D and by height exception an OMF would be permissible per ASCE 7-10.
1. HSS column & HSS Beam; my understanding these are permissible shapes for an OMF per AISC 341 (although not really addressed in the specification)...what about connections that would satisfy 341's OMF requirements? Is a simple fully welded connection if strength checks per 341 permissible? What about continuity plates requirements?
2. HSS column & WF Beam; what about connections? AISC 360 & Design guide 24 shows some options for FR connections...I assume these would be permissible for an OMF 341?
3. Built up WF & WT cruciform; is this permissible to treat as classic WF moment frame in both axis and use typical WF prequalified connections?
1. HSS column & HSS Beam; my understanding these are permissible shapes for an OMF per AISC 341 (although not really addressed in the specification)...what about connections that would satisfy 341's OMF requirements? Is a simple fully welded connection if strength checks per 341 permissible? What about continuity plates requirements?
2. HSS column & WF Beam; what about connections? AISC 360 & Design guide 24 shows some options for FR connections...I assume these would be permissible for an OMF 341?
3. Built up WF & WT cruciform; is this permissible to treat as classic WF moment frame in both axis and use typical WF prequalified connections?






RE: One Story Biaxial Ordinary Moment Frames Options Per AISC 341
As a disclaimer, I'm probably wrong about at least one of those statements.
RE: One Story Biaxial Ordinary Moment Frames Options Per AISC 341
RE: One Story Biaxial Ordinary Moment Frames Options Per AISC 341
For biaxial, your options are limited. There is a proprietary HSS column connection that's biaxial and described in 358 (or one of its supplements). But, if you want to stick with a wide flange, then you would probably have to Cruciform it (i.e. weld WT's of the same section to each side) and go with one of the 358 connections. I don't see any other way to develop the probable beam strength in the weak axis connection otherwise.
Alternatively, I suppose you could say the hinging occurs in the column instead. There is an example (I believe) in the Seismic design manual where they do this at the roof level of a building. So, it is allowed....