Coupling of columns thru slabs 1

[blihp]

hi

i have a building where i have a couple of columns relatively close to another and am finding that they are attracting axial loads under a lateral load only case (ie no gravity or live loads).

The columns are pinned and thus it cant be frame action (and the results show they are carrying no shear). So the columns only have axial load in them, no shear.

I have modelled the slabs as shells (ie 6 dof); do you think this may be a cause of the problem? (i dont want to spend a day trying something that is unlikely to be the problem...)

I have also tried refining the mesh, which did help but didnt alleviate the problem. The only thing that did help was reducing the stiffness of the slab to a very low value of modulus (ie 1% of full E), but im unhappy with this for other reasons.

I can only assume that they are acting as some sort of coupled truss through the slab. As i am using ETABS to design the cores/walls, i want to have all the stability to be taken by the cores/walls and not be lost in other elements. I will ensure these other elements are ok under lateral loads separately.

any suggestions?

many thanks in advance


"a wise man know his limits" anon.
blihp

 

[stressed]

Long time with no answer from anyone. Without seeing your model, my only advice is to make double sure the "lateral" load case/combo does not have a gravity component. Go under your Define load case menu and check to make sure you didn't include a self weight multiplier of 1 to this case.