Irregular Lateral Force Resisting System - Edge Columns + Masonry
Irregular Lateral Force Resisting System - Edge Columns + Masonry
(OP)
Structure is 60' x 21' and 45' high.
There's 60' of 8" masonry shear wall in one direction but in the other direction we have excessive openings so there will be cold formed curtain wall with steel framing for lateral at each end of the building. Two columns spaced at 21' is giving me unacceptable drifts and is economically not worth it. I added an additional column and obtained reasonable sections with acceptable drifts. The owner is having a panic attack and demands two columns per side. EoR is claiming that I can consider contribution of lateral stiffness of the 60' masonry wall. My issue is how do I approach this? Realistically I know that the wall will provide some stiffness but do I assume an equivalent column section and analyze my diaphragm as a continuous beam with a spring in the middle to represent the wall? Do I anchor the column to the masonry and consider it a composite section? What would the effective width be?
I appreciate any help.
There's 60' of 8" masonry shear wall in one direction but in the other direction we have excessive openings so there will be cold formed curtain wall with steel framing for lateral at each end of the building. Two columns spaced at 21' is giving me unacceptable drifts and is economically not worth it. I added an additional column and obtained reasonable sections with acceptable drifts. The owner is having a panic attack and demands two columns per side. EoR is claiming that I can consider contribution of lateral stiffness of the 60' masonry wall. My issue is how do I approach this? Realistically I know that the wall will provide some stiffness but do I assume an equivalent column section and analyze my diaphragm as a continuous beam with a spring in the middle to represent the wall? Do I anchor the column to the masonry and consider it a composite section? What would the effective width be?
I appreciate any help.






RE: Irregular Lateral Force Resisting System - Edge Columns + Masonry
If the unreasonable drift is in the 21' moment-frame direction, the wall in the other direction won't help much, regardless of the attachment.
RE: Irregular Lateral Force Resisting System - Edge Columns + Masonry
RE: Irregular Lateral Force Resisting System - Edge Columns + Masonry
If it were all masonry I guess you would have an L shaped piece, but I don't see the flange of the "L" helping the stem when the stem is a moment frame.
I suppose you could model it and see what those connecting forces look like. If the structure were not so tall there might be some nominal flexural stiffness to be gained by including the CMU in the cross direction. I can't picture it curing what ails the structure.
Once you figure out if it helps you, then you can consider attachments. Usually CMU attachments have some flexibility in its attachment to the building frame and this might hurt your chances to force them to work compositely.
Sounds like a red herring.
RE: Irregular Lateral Force Resisting System - Edge Columns + Masonry
RE: Irregular Lateral Force Resisting System - Edge Columns + Masonry
Is the layout of your end wall penetrations such that you might be able to create a two tier moment frame? You know, looking like a two story moment frame but without a diaphragm behind the lower level.
I agree with Decker about the intermediate frames as well. 60' x 21' is starting to get up there with regard to diaphragm aspect ratio.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.