capacity analysis of two-way slab

huangyhg

capacity analysis of two-way slab
i need to check an existing 8" thick two-way concrete slab for an eccentric distributed load of mechenical equipment of 60 psf. the dead load of the slab is 100 psf in addition to permanant dead load of 40 psf. the total load on the panel is 200 psf. it is a 24'x15' typical interior salb panel. the existing salb was reinforced with #4 @ 12" each way.
i have analysed the floor for its capacity using the direct design method of aci, and found that the existing reinforcement is inadequate.
is there any other way to check the existing salb for its capacity? whether my calculations are correct, or am i missign something?
thanks for your time
sree
bannu,
have a second look at the slab. you might be assuming it to be a simply supported slab which will be a very coservative way of looking at it if the corners of the slab are anchored to the support or are held down by weight above. the corners and edge conditions of a slab are very critical parameters if you want to assess the capacity of it.
regards,
flame
i generally use the equivalent frame method to analyze a two way slab.  you need at least a 2d frame analysis computer program to do this.  pca's adoss program is an even better way to analyze this.
if you continue to find the slab is inadequate, perhaps redistribution of moments will help.
daveatkins
the yield line method is probably the one you want as you can use it to analyse any load condition on the slab.  it does require a bit of practice to be able to postulate where the yield lines for the particular support and load conditions will lie.  most text books on structural analysis should give you the method.