Portal Frame Analysis with semi rigid base plate connection Portal Frame Analysis with semi rigid base plate connection flyingdebris (Structural) (OP) 21 Aug 13 01:01 Is there any reference in any aussie code or manual to design a portal frame with a semi-rigid base plate connection? Would anyone know how to do this/analyse in space gass? RE: Portal Frame Analysis with semi rigid base plate connection asixth (Structural) 21 Aug 13 04:20 Just responded to this in the structural other topics forum. You will find reference to a previous discussion on this matter there. I'll repost here anyway. thread744-260012: Base Stiffness and AS4100 I haven't used spacegass in a while but instead of assigning a fixed moment restaint you assign it free and give it a rotational stiffness. Might be something like 1E6 (N-mm/rad) under the Kz or whichever way you have your frame orientated. RE: Portal Frame Analysis with semi rigid base plate connection flyingdebris (Structural) (OP) 21 Aug 13 20:40 Thanks asixth, that makes it a little clearer after reading all that. My concern is designing a cold formed portal frame with a moment base connection. The column base connection comprises of a large bracket cast into the concrete with each flange of the bracket being bolted to the two column flanges. This connection no doubt will take a significant amount of moment in the structure. Is there a way to convert this moment connection into a stiffness I can input into my calculations/space gass?? I realise that cold formed portals should probably be done by plastic analysis, but I want to know about the connection stiffness also. Can you offer any comments on that? RE: Portal Frame Analysis with semi rigid base plate connection asixth (Structural) 21 Aug 13 23:33 Not really. I don't design cold formed other than propriety purlins and the occasional metal stud wall. Whenever I'm looking at moment transfer at the base plate I generally play around with the rotational stiffness until I achieve the balance between moment transfer and base rotation that I feel comfortable with.