huangyhg

help with fe concrete flat slab design
i am designing a reinforced concrete flat slab using fe and am seeking advice on the distribution of hogging moments over columns. the slab is supported on 450x450 columns which i have represented using pinned supports. as would be expected i get very large hogging moments at these nodes. these quickly reduce as i move away from the restrained node.
when designing the reinforcement to go over the columns i need to distribute the hogging moments over the width of the column strip in the slab. any advice on how to do this would be gratefully received.
thanks,
neil.
some clarification is needed:
are you using a general fea program or a program like safe that's specifically designed for concrete slabs?
you said that you're using pinned supports to model the column. does that mean that you have a shell mesh with a single node restrained against translation in all directions?
the question for these usually has more to do with the amount of unbalanced moment going into the column for punching shear design, but it seems like you're typing more about the typical negative moment in the slab. the moment going into the column can't be ignored. if you're using a pin at a single node, then this moment transfer won't be modeled.
14159
using pinned supports is absolutely fine for the design of the slab reinforcement, as you will get a slightly conservative hogging moment.
you will need to analyse again with rigid supports to obtain column moments and do the punching shear check.
it is acceptable to use the average moment over the column width e.g. if you had a 1mx1m column, the hogging moment over a theoretical pin head support would never occur.

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