In this article (and video above), we solve a force analysis problem of a field fabricated floor joist constructed by nailing together two boards, to help you prepare for your PE Exam. This week’s problem was created and solved by Enrique Ivers, an Engineer in Training.
Question:
A field fabricated floor joist is constructed by nailing together two boards as shown in the figure to the right. If the nails are spaced at s = 6”, what is the shear force (lb) in each nail if the section is subjected to a transverse shear force = 1.0 kips?
Explanation:
We should assign a datum at the bottom edge of the section (at the bottom of the 1.5 x 5.5 in board) to be our neutral axis.
We can then calculate the y-coordinate of the centroid:
We can now use the shear stress equation to calculate the shear stress at the interface between the two boards:
Answer:
The correct answer is D.
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I hope you found this article helpful. In upcoming articles, I will solve some more PE exam practice problems and answer other questions from our subscribers. Pass the PE Exam videos will publish weekly, so be sure to click the subscribe button so you don’t miss something that could make a substantial difference in your exam result.
Lastly, I encourage you to ask questions in the comments of this video, or on this page and I’ll read and respond to them in future videos. So, if there’s a specific topic you want me to cover or answer, we have you covered.
I’ll see you next week… on Pass the PE Exam
Anthony Fasano, P.E.
Engineering Management Institute
Author of Engineer Your Own Success
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