NCEES Sample Questions and Solutions

[brosenbe]

Hi all. In the solution to problem 603 of the NCEES sample questions, part a (Page 100), the answer takes a tributary width of the one-way slab to determine the load on the beam. Then, it uses the ACI coefficients to determine the shears and moments in the beam (as requested in the problem). However, why do you not also have to use the ACI coefficients to determine the load on the beam? Why can you just use a tributary area of the one way slab? Section 8.3 of ACI references beams and one-way slabs, so it seems that these would apply, and you would find the shear on each side of the beam from the slab loads (exterior face of first interior support, and all other supports) and add them? Any help would be much appreciated. (The answer is pretty close to taking a trib area (which makes sense), but I could see it differing depending on the magnitude of the applied loads.

 

[mjbikes]

Hi all. In the solution to problem 603 of the NCEES sample questions, part a (Page 100), the answer takes a tributary width of the one-way slab to determine the load on the beam. Then, it uses the ACI coefficients to determine the shears and moments in the beam (as requested in the problem). However, why do you not also have to use the ACI coefficients to determine the load on the beam? Why can you just use a tributary area of the one way slab? Section 8.3 of ACI references beams and one-way slabs, so it seems that these would apply, and you would find the shear on each side of the beam from the slab loads (exterior face of first interior support, and all other supports) and add them? Any help would be much appreciated. (The answer is pretty close to taking a trib area (which makes sense), but I could see it differing depending on the magnitude of the applied loads.

You would use the 1.15wl/2 for the shear of the slab spanning D to C to analyze the shear capacity of that slab at the beam. For the beam loading, the tributary area is correct.