Concentrated Load on Two-Way Slab

[wubwub]

I have a concrete building with 30X30 column bays with a two-way waffle slab. The client has placed a concentrated factored load of about 10,000 pounds loacted about 7.5 feet from the column in each direction without anyone performing a structural analysis. I have been tasked to determine whether the additional concentrated load is causing any overstresses in the slab.

I have ADOSS in the office, but it does not compute the local stresses from this concentrated load. It essentially says to compute it manually.

I have not been able to find any good sources on how to distribute this load to determine the effect on the capacity of the slab. Is there an easy way to do this or any good source that may help me in determining whether the slab capacity is sufficent for this additional load. One way I thought of was to use the Strip Method, but I am perplexed on how to break up the load into the two directions.

Any help would be appreciated.

Thanks.

 

[JAE]

Your load is situated right on the edge of your column strip. I would simply enter your load in ADOSS at the 7.5 ft. location and re-analyze/design. Even though it is offset from the column centerline, the analysis and design method prescribed by ACI is very conservative as you are providing reinforcing in both directions for the same load. (assuming you use the equivalent frame method as in ADOSS)

With the new load - there is the rational possibility that the original live load that was used in the design of the slab cannot occur in the area under your object causing your new load. You can take advantage of this by limiting your applied uniform live load in this area.