effective area for flexure

huangyhg

effective area for flexure
i have a client who wants to add a point load on an existing slab.  i have checked the slab for punching shear but am not sure how to check for flexure.  because the slab is a large area, i am not sure how far from the new column the effective area will extend.  any advice will be appreciated.   
check out our whitepaper library.
do a finite element model for a simple grid (bounded by at least 4 columns), and perform comparasion on stress changes for with and without the add'l concentrated load, it should be ok if increases are within 10%.
is this a slab-on-grade or an elevated slab say the second floor?   
check this paper out.
a paper called "practical yield line design" is quite good.
it is a slab on grade.
thanks for all of the help and advice.