yes you are correct I forgot to mention that that there are five ducts in this beam. only the middle duct was used to adjust the sweep on this beam.
Using LRFD the allowable concrete strength is 0.6 x fc' with fc' = 10 ksi, so I get an allowable concrete strength of 6 Ksi. Now the force applied is 21 kips, also keep in mind that this force was applied only at the middle duct, which means it will be distributed on the diaphragm of the beam which has an area of 518 in2 (14" x 37"). 21,000 lbs / 518 in2 = 40.5 psi. That's what I get.
is that all I have to do, to check that concrete will not crush at the ends? am I missing any thing?