NCEES Practice Exam

[lhpriest]

In the solution to part (B) of this problem, next to the calculation of the effective area for the parapet, the text reads: " <10 ft OK. " In the next couple of lines there is a note stating: "Note: Effective area for roof could be taken as more than 10 ft^2".

Does anyone know where the 10 ft^2 number comes from? I have looked in ASCE-7 and IBC 2006, but I haven't had any luck finding the reason for the check against 10 ft^2. It seems I must be missing something...

Any help is appreciated!

 

[lhpriest]

I'm not sure why the emoticon showed up, it is supposed to read part "b".

 

[mjbikes]

In the solution to part (B) of this problem, next to the calculation of the effective area for the parapet, the text reads: " <10 ft OK. " In the next couple of lines there is a note stating: "Note: Effective area for roof could be taken as more than 10 ft^2".
Does anyone know where the 10 ft^2 number comes from? I have looked in ASCE-7 and IBC 2006, but I haven't had any luck finding the reason for the check against 10 ft^2. It seems I must be missing something...

Any help is appreciated!

The first line you questioned got me, too. (Should read "...5.3sq.ft. < 10sq.ft.") I figured it refered to the wind charts on 6-11A&B. There is a threshold at 10 sq.ft. below which GCp is constant.

The second one is based on roof area. SInce there is not enough information in the problem GCp can be taken at 10sq.ft. (worst case).

 

[Ble_PE]

In part c of the solution, shouldn't b = 6t = 45.75"? I know it doesn't really make a difference in the problem since the wall is overstressed, but I wanted to make sure I was correct in my design.

 

[lhpriest]

In part c of the solution, shouldn't b = 6t = 45.75"? I know it doesn't really make a difference in the problem since the wall is overstressed, but I wanted to make sure I was correct in my design.

In MSJC 2.3.3.3.1b, the code reads " Six times the nominal wall thickness." I would interpret the nominal thickness of an 8" CMU wall to be 8" rather than 7 5/8" which would be the actual thickness.

 

[patik83]

In part c of the solution, shouldn't b = 6t = 45.75"? I know it doesn't really make a difference in the problem since the wall is overstressed, but I wanted to make sure I was correct in my design.

In MSJC 2.3.3.3.1b, the code reads " Six times the nominal wall thickness." I would interpret the nominal thickness of an 8" CMU wall to be 8" rather than 7 5/8" which would be the actual thickness.

Also, in part b, I would have thought that a_p for a parapet was 1.0, not 2.5, based on the table in ASCE 7 Ch. 13. This reduces F_p to 20.2 psf. Let me know if I'm missing something...

 

[lhpriest]

Since the parapet is attached at the roof level, it is considered to be braced to the structural frame below its center of mass which requires ap of 2.5.

 

[patik83]

Since the parapet is attached at the roof level, it is considered to be braced to the structural frame below its center of mass which requires ap of 2.5.

ahh, I see. I looked through Table 13.5-1 too quickly... I guess if you had 45 degree struts supporting the top of the parapet, you could use ap = 1.0, since it would be braced back to the structure above its CM.

Thanks,

 

[Ble_PE]

In part c of the solution, shouldn't b = 6t = 45.75"? I know it doesn't really make a difference in the problem since the wall is overstressed, but I wanted to make sure I was correct in my design.

In MSJC 2.3.3.3.1b, the code reads " Six times the nominal wall thickness." I would interpret the nominal thickness of an 8" CMU wall to be 8" rather than 7 5/8" which would be the actual thickness.

Looks like I need to work on my reading comprehension a little, but that's no surprise considering I'm an engineer!

Thanks, I completely missed the nominal in the code and I didn't have it written out in my notes.