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NCEES 2008 Problem 110 - Need Assistance


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#1 Lucky1

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Posted 06 November 2011 - 02:47 PM

This appears to be a simple sum of the moments type problem complicated only by the angle of the uniform load. However, looking at the solution there are numbers that are not making sense. Can somebody walk me through this? Thanks.

#2 civilized_naah

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Posted 06 November 2011 - 05:04 PM

This problem has been discussed several times before. The solution given by NCEES is inconsistent with the problem statement. There are two possibilities:
1. The uniform load on the stair slab is 0.45 klf on horizontal projection (this is how the figure shows it), in which case the rise of the stair does not matter. The resultant force is 0.45 klf multiplied by the horizontal projection length of the stair and is located exactly at the center of this horizontal projection.
2. The uniform load on the stair slab is 0.45 klf acting normal to the stair slab (this would make sense if it was a wind load rather than a gravity load) (this is how the solution seems to assume it, even though it does not account for the horizontal component of the resultant). The resultant horizontal force is 0.45 klf multiplied by the vertical projection length of the stair and the resultant vertical force is 0.45 klf multiplied by the horizontal projection length of the stair and these are located exactly at the center of the stairway slab.

I do not have the book in front of me and am writing this from memory, but either way you look at it, the statement of the question and the solution are inconsistent.

#3 Lucky1

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Posted 07 November 2011 - 02:47 PM

I was wondering how I was missing something that should be relatively simple. Thanks for the assistance.



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