Baseplate - Large Moment - Anchors within flanges - AISC Design Guide 1? 5

[StructureMan44]

I'm attempting to make a 11"x11" baseplate work below a W10x49 subjected to 20k-ft moment and 10kip shear in both directions, and a 2 kip tensile load. I'm trying to place the anchors within the column flanges. The column loading creates a "large moment" situation per AISC design guide 1 section 3.4. When placing the anchors between the flanges what values should be used for n and m? This impacts the equations given for determining the minimum plate width. Also is it likely that the baseplate would have no area in bearing and instead two of the four anchors resist the moment and uplift entirely?

 

[BridgeSmith]

I'll second hokie66 on JoshPlum's summary being excellent. I would just add one thing - along with the stiffness of the base plate, the axial stiffness of the bolts and the distance between them can also be factors in the overall stiffness of the connection.

 

[ash060]

I have considered an arrangement with the anchors inside the flanges as fixed and transmitting moment. I thought about flush end-plate moment connections like they use in metal buildings. The two are pretty similar except for the concrete part. If you are developing a similar force in the anchors as you would in the bolts (of the flush end plate) I would imagine the baseplate would develop similar capacity.

I also remember seeing something about baseplate fixity in the PCI Handbook, but can be sure about it.

 

[BridgeSmith]

"The two are pretty similar except for the concrete part."

That can be a fairly substantial exception. A through bolt in a metal building has a very short deformation length, but an anchor bolt embedded in concrete will allow more rotation of the connection under the same stress due to a longer length of the bolt allowed to stretch.