@bones206: yes & by calculation. The beams would fail badly if those are not considered bracing points.
@lexpatrie: Thank you! Do you have any info on the roof deck? (the building was built around 1964)
Thank you for sharing your thought!
Fyi, I am thinking of creating braced frames (between two joists, see below photo) at existing steel angle locations and use the frames to brace the beam. I would detail the connection to allow the joists to deflect vertically.
Again, thank you!
Hello fellow Engineer,
Our office is asked to evaluate an existing roof framing structure that was modified previously due to the addition of a higher roof. Please see attached photos below.
You will notice that, in order to handle the new drifting snow load, the following modifications were...
@JAE:
Thank you for your comments/ answers.
1. I agree with you about how the drifting snow should be calculated per ASCE 7. However, I still have a hard time making sense of it when comparing the calculated drifting snow loads of building with very steep (say 12:12) roof and that with flat...
Hi everyone,
When you have a chance, could you please take a look at my following questions and attached sketches (2 PDF files), and let me know your thought/ comments.
• Code: ASCE 7-10
• Ground snow load: 50 psf
• Ce = 1.0
• Ct = 1.0
• Is = 1.0
• Cs = 0.75 for 10:12 roof
• Cs = 1.0 for 7:10...
This is great :)
The second point on my original post concerning of the lack of blocking between rafters for transferring shear load from diaphragm to shear wall when wind is parallel to ridge. For wind perpendicular to ridge, I do not concern about the connection between diaphragm and shear...
Koots: You are correct. I did not think about that. Have you tried to compare the unit shear = [chord force (T = C = M/W) / building length] with the shear flow using the beam equation abobe?
Flexible diaphragm (wood) does not distribute shear to (perpendicular to load direction) shear walls. Hence there is no shear that direction. One will not design wood shear wall (in plane shear) for wind perpendicular to shear wall.
Rigid diaphragm: yes
Yes I totally agree with you on horizontal shear in beam and am familiar with it (especially when designing built-up girder and/or reinforcing existing I-beam with plates)
However, we are talking about diaphragm and horizontal beam is its analogy. I am not sure if it is appropriate to utilize...
Kookt,
I have just click to "submit post" while intending to "preview".
If that the case, the concerned unit shear would equal V/(building length)? and if the building length is not significant shorter than "W", then it should not of a concern.
Just my 2 cent
KootK,
Could you please elaborate that a little more? A mark-up on my sketch wood be better.
I thought the FBD on the left of my sketch suffices to demonstrate my point of not worrying about the little gap at the ridge (due to ridge vent).
Is it the unit shear (parallel to the ridge, at or...
