NCCES Civ/Structural Problem 509 Errata, how is shear center calculated?

PowerStroke79_PE · Sep 10, 2017

I downloaded the NCEES Civil Structural Practice Exam Errata. For problem 509 there is no showing how they acquired the shear center of the L shape in order to solve the problem. This is in fact the KEY to solving this problem. Why wouldn't they show it? The original solution in the practice exam is based on the centroid of the member (x direction) and they show how they resolved. I realize getting the shear center is considerably more involved than the centroid, but shouldn't they have included the approach for that part of the problem? Below is a link to download the Jpeg of the Problem 509. I tried uploading but it says only 102 kb. Looking forward to responses.

https://1drv.ms/f/s!AgdYdMOsCE0lgthTPKw4mCgoIMOqtA

DrZoidberWoop · Sep 11, 2017

Unless I'm mistaken, the solution procedure should be similar to problem number 514 or something like that. A purely vertical load on the support leg of an "L-shaped" member. Don't have it in front of me now. Also this exact issue was brought up on the forum of another site. Quick google search should get you there.

PowerStroke79_PE · Sep 11, 2017

DrZoidberWoop said:
Unless I'm mistaken, the solution procedure should be similar to problem number 514 or something like that. A purely vertical load on the support leg of an "L-shaped" member. Don't have it in front of me now. Also this exact issue was brought up on the forum of another site. Quick google search should get you there.

Ok, I very fast realized you were referring to problem 514 from the old NCEES Practice Exam, before 2015 version, and I have the 2015. Luckily I also have the previous version!

Someone from this forum was very kind to send me their copy for studying purposes. (Thank you @joy21 ! )

Now, I would really like to get the errata for the previous version of the NCEES exam as I suspect problem 14 will have a correction as problem 509 does. Still a little in the dark about exactly how these problems should be solved, here is what I understand so far.

1. In an asymmetrical beam, "the bending axis passes through the shear center, not the centroid." (CERM 15th ed. Pg 45-17 - references will be from here-)

2. The torsional eccentricity is the distance between the shear force and the shear center. Therefore giving the torsion moment.

a.) The torsional moment is NOT the P*e base on the centroid of the asymmetrical member, but P*e based on the shear center and the distance to load P (or V for shear).

I still don't think they would make us calculate the shear center of an asymmetrical member, but Its just a wild guess. I really don't have any experience to back it up. So all in all, I think problem 514 also should be corrected since the solution is based on the centroid. But, I have in fact not passed my PE and have a lot to learn. I appreciate the help and can only ask for more. I will keep digging and googling.

Thanks,

allecram513 · Sep 12, 2017

Hemi79 said:
Why wouldn't they show it?

My impression was that the errata was showing the shear center as given. Not calculated as a part of the solution. Note that they have it labeled in both the question and the solution. Make sense?

PowerStroke79_PE · Sep 12, 2017

allecram513 said:
My impression was that the errata was showing the shear center as given. Not calculated as a part of the solution. Note that they have it labeled in both the question and the solution. Make sense?

and that would make it perfect to solve. Thanks for pointing that out!