INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Jobs

Snow Load 7-02, 7-05, Cold Roof Cs Questions

Snow Load 7-02, 7-05, Cold Roof Cs Questions

(OP)
I have a cold roof with Ct = 1.1. Roof slope is 6:12 or 26.6 degrees. It's an unobstructed slippery surface.

Using Figure 7-2b, it looks like Cs = about 0.8.
Using equation C7.4 2(a), Cs = 1.0 - (slope - 10°)/60° = 1 - (26.6 - 10)/60 = 1 - 16.6/60 = 0.72.

Which is it: 0.8 or 0.72?

Are there some notes I'm missing? Are my eyes playing tricks on my concerning using the graphical solution rather than the equation?

Any assitance is most appreciated, etc.

RE: Snow Load 7-02, 7-05, Cold Roof Cs Questions

DaveViking,

I don't think you missed anything.  I compared the graph to the equation in ASCE 7-0052.  Note on the graph in Fig. 7-2, at the top end of the inclined portion of the dashed line.  It's marked 10 degrees, but that's not where its located.  I'd say they drew that line wrong in the graph.  If you pencil in a line that goes from (0,70) to (1.0, 10) it looks like your case reads about 0.72 on the graph, just like the equation.

In ASCE 7-02, the graph looks like it is correct.  


regards,

chichuck

RE: Snow Load 7-02, 7-05, Cold Roof Cs Questions

(OP)
Holy Cow! You're right!!!

Alert to ASCE: REVISE THE FIGURE!!!

RE: Snow Load 7-02, 7-05, Cold Roof Cs Questions

It looks right in my 7-02 - I get 0.74 on the graph.

RE: Snow Load 7-02, 7-05, Cold Roof Cs Questions

Their correction of Fig. 7.2 in ASCE 7-02 looks like it changes the graph in Fig. 7.2b from right to wrong.  I don't see any correction to Fig.7.2b in ASCE 7-05 at that page.

regards,


chichuck

RE: Snow Load 7-02, 7-05, Cold Roof Cs Questions

(OP)
You are correct! The erratta needs an erratta! It turns out (according to research outside of Eng-Tips) that a lot of people have copies of ASCE 7-02 and 7-05 with the correct figure and a lot of people have them with the incorrect figure. My advice to the folks in my office is to simply plot the equation an past it into the book. That, or draw a red line in the corrst location in the book.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close