huangyhg

r factor and moment frame detailing
i haven't designed many moment frames, but i am working on a rather simple one that is part of a "canopy". the structure is only 15 feet tall and is very light. snow loading generates the highest moments in the frame, not seismic. it is in sdc=d.
i would like to simply "lock up" the joints by welding/bolting with standard "old-fationed" details and beam over column joints. my question is: can i avoid the detailing requirements of the aisc 341 in any way? i seem to remember reading somewhere that if you use a response mod. factor = 1.0, some of the requirements may go away.
thanks for any guidance you can provide.
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i haven't heard of using an r of 1. i have used r=3 to avoid the aisc 341 requirements as allowed by item #8 of ibc table 1617.6.2. however, if you are in sdc d, e, or f, this is not permitted, regardless of the controlling load case. the seismic provisions must be used.
thanks rrmiv.
the main thing i am trying to simplify is the column to beam connection. i have no problem meeting the strength requirements of the provisions, but i would like to avoid the weld access holes, weld backing treatment, etc. reading the provisions for an omf, i notice it states things such as "when steel backing is provided", or "where weld access holes are provided". it does not imply that these things "shall" be provided. would i be in violation if i don't provide those details?
rrmiv is correct. sdc d requires a smrf which entails using the pre-qualified connections, probable plastic moment capacity, strong column/weak beam, etc. all this seismic strength detailing stuff would be easy to satify for a one story canopy and your only issue (probably) would be having to use a pre-qualified rigid connection.
i believe i can use an omf in this case based on asce 7-02 table 9.5.2.2, footnote i.
of the prequalified connections (fema 350 and aisc 358), some have weld access holes, some have backing bars, etc. not all of these items are used in each connection. i believe what is intended is that when you choose a connection with one of those items, you have to do it a certain way. the prequalification requires that the stipulated details of a connection must be complied with - they are not optional. otherwise they are no longer pre-qualified.

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