built up column weld
built up column weld
(OP)
Hello,
I am designing a built-up "cruciform" column as part of a rigid frame (using R=3.0) to resist wind and seimic loads. I am uncertain of how to design the weld of the WT webs to the web of the continuous wide flange column. I am thicking about doing a shear flow calculation for the bending forces in the column and sizing a fillet weld on either side to the WT webs. Is there any other forces I need to add in?
I noticed that the seismic design manual (section 2.3.2b) calls for a zone extending 12" above and 12" below the beam where the WT's are attached with a CJP weld AND a pair of reinforcing fillet welds. Is this recommendation a good idea (or just extra expense), if we are in a low seismic area and not using a special or intermediate moment frame? I appreciate any comments.
I am designing a built-up "cruciform" column as part of a rigid frame (using R=3.0) to resist wind and seimic loads. I am uncertain of how to design the weld of the WT webs to the web of the continuous wide flange column. I am thicking about doing a shear flow calculation for the bending forces in the column and sizing a fillet weld on either side to the WT webs. Is there any other forces I need to add in?
I noticed that the seismic design manual (section 2.3.2b) calls for a zone extending 12" above and 12" below the beam where the WT's are attached with a CJP weld AND a pair of reinforcing fillet welds. Is this recommendation a good idea (or just extra expense), if we are in a low seismic area and not using a special or intermediate moment frame? I appreciate any comments.






RE: built up column weld
One item: Why can't you use a weak axis moment frame for the second direction? From what I remember if you are using ordinary moment frames in a low sesimic design category then you could use weak axis moment frames (with some exceptions). Are you stiffness controlled?
As a side note, weak axis MF connections perform better than strong axis connections due to the force flow (emphasis on connection performance! not stiffness of system performance!). There is an AISC article on this.
RE: built up column weld
RE: built up column weld
The full depth stiffeners are a good idea, and I always include them on any moment frame for load continuity, even if you can get away without them in low seismic zones (designed using the concentrated load section of AISC). I don't think you can use them to aid in web shear transfer forces.
I think you should CJP and provide a reinforcing fillet. The columns will probably be shop welded anyway.
Have you considered a box column? or arranging two columns with the column flange of one nested inside the web of the other (This could eliminate the cruciform)? ...or offsetting the two columns?