SE Practice Exam Problem Questions 1

[Br_Engr]

Good morning -

Full disclosure - I practice in the bridge field, so I am re-acquainting myself with some of the provisions of AISC. Forgive me if these seem 'basic', but rest assured that, if successful, I have no intention of dabbling in the "dark arts" of the building realm...

1. I was working a practice exam for the upcoming SE and had a question about the base plate design problem (AM Vertical; Problem 121)

First, NCEES did not provide the column section in the problem statement, but that is a QA issue. My question is in the solution. Did they omit the 'omega' factor for computing "X"? It seems that a 2.31 factor is missing and this would seem to blow the problem up.

2. Solved a wind problem (AM Lateral; Problem 102) using the "Directional" method. Solutions used the "Envelope" method. Same answer. Question is when to use one over the other? Logic says use directional when there are ground conditions differ depending on direction of wind (i.e. hills to the east, open ground north/south (like a valley).) I am assuming that if they want you to use the direction procedure on the exam, they will give you the varying conditions. If the problem is phrased "generically", envelope is the way to go.

Thank you in advance for any help you may provide.

 

[RWW0002]

I have the 2011 version of NCEES sample questions and it states a W14x53 column (see snip below). I am sure this is older than your version, but it is odd that Q121 is still a base plate design problem. If nothing else, this will give you another sample problem to work.

As far as wind procedures, I would recommend being familiar with all methods in case they ask for one specifically, but mostly practicing one method for primary use. Envelope procedure will likely be the simplest for low-rise buildings. It is generally building height (or familiarity) that kicks you to the Directional Procedure.

 

[Br_Engr]

Thanks RW. I have a 2011 version as well and that problem was straight forward. BUT the solution for that one (2011) did NOT use the concrete check, rather the allowable column load. The 2017 edition uses the allowable bearing stress as the limiting value for computing X.

 

[Br_Engr]

I did find the "Errata" where they provide the column section in the problem statement.

But there was no correction for the "Omega" factor in the solution. What am I missing?

 

[dauwerda]

Yes, it does appear that the ASD solution is missing the omega factor (which should be 2.5). If it had been used the X value should be 0.854 which would result in a lambda value of 1.33.

However lambda can not be taken greater than 1 and can conservatively be assumed to = 1. So, this error does not change the overall result of the problem, where they (not so conservatively as they thought) used lambda equal to 1 to calculate lambda n prime.

 

[STrctPono]

I went back to my Practice Exam from a few years back and noted a few inconsistencies with that problem. At the time I was passionately into everything concerned with the exam. I could have written a book about it and all the mistakes in the SE Reference Manual when I was done.

 

[WARose]

One word of caution (and keep in mind: it's been about 10 years since I last took a NCEES exam or studied one of their test exams)......I saw some sample problems where they worked out a full solution when the same answer was in a table somewhere. As a example, on a wood problem, they worked out the full solution for the various failure modes for a bolted connection. (I.e. the "Z" equations in NDS.) And you could have gotten the same answer in NDS's tables.

I doubt there would be a table in the AISC manual for what you are doing....but I just wanted you aware.