New load on existing CIP flat plate

[maxwolf]

Am trying to determine a code compliant method to determine if a new, higher live load can be accomodated by an existing CIP plate. Plate: 8", 4ksi with only bottom bars (#4's @13" ea way) explicitly stated. Top bars indicated only with codes that refer to a lost drawing. Overall the building appears in good condition. Using FE (RF-Concrete in RFEM), have determined req'd area of steel (A_s)and internal forces (image example below). Area of stl determined for bottom bars is within the #4's @ 13. The new concentrated load is quite small(a few kips compared to 40psf per code), so the difference between the two cases is tiny - possily within the limits of precision for any analysis. Suggestions?

Added image. A 2 way slab, irregular col grid.

 

[JLNJ]

I’m not seeing the image.

Is this a one-way or two-way slab?

What is (are) the span(s)?

#4’s at 13” is pretty light for an 8” slab.

When you check it by hand, what do you get?

 

[r13]

Check shear in addition to bending stress.

 

[university_professor]

check cross section.