huangyhg

eccentricites generated in "pin-ended"edge columns
i'm involved in the design of a building which has concrete flat slabs supported on internal walls and perimeter columns. i had thought that one could consider the columns as pin-ended and just design for moments due to "nominal" eccentricities - but the longer i think about it the less sure i am...
i'm interested to know if you know of any design guidance or research relating to the moments generated in "pin-ended" edge columns due to the rotation of the slab and the consequent change in position of the point of load application.
perhaps it is a bit of a theoretical question, but nonetheless i'd be very grateful for any pointers you could give me.
my 2c, for what it's worth ...
if the slab rotates wouldn't that mostly change the direction of the load, producing a side component, which would change your column into a beam-column ?
mind you, if the slab rotates that much, is the building good for anything ?
probably not worth 2c ...
you can get design moments from stiffness methods or from the aci moment coefficients. if you're using a program like adoss, it should give you the moments.
my experience is that they usually don't amount to much, but there are exceptions, so should be looked at, at least briefly.
the unbalanced moment must transfer into the column. the unbalanced moments are generated due to unequal length of adjacent spans, unequal loading of the spans and patterned live loading to produce controlling moment.
better analyzed with a finite element model to check the moment distribution keeping column pin or fixed. it would be easily checked in a safe program specifically for slab designs with a variety of situations. i don't think so adoss can cater for wall, it'll ask for you internal column size.

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