×
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!
  • Students Click Here

*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.

Students Click Here

Jobs

Why divide elastic deflection by I (asce 7-05, 12.8.6)

Why divide elastic deflection by I (asce 7-05, 12.8.6)

Why divide elastic deflection by I (asce 7-05, 12.8.6)

(OP)
ASCE 7 requires deflections to be checked by multiplying the elastic deflection by the deflection amplification factor and dividing by the importance factor. What is the purpose for dividing by the importance factor? Just applying quick knee jerk logic, one would assume that as we increase the importance factor for a more critical structure, we would want tighter requirements. However, this larger importance reduces our design deflections - WHY?

RE: Why divide elastic deflection by I (asce 7-05, 12.8.6)

Deflection limits are a serviceability issue not a life safety issue, arbitrarily reducing allowable deflection limits does not increase life safety.  

RE: Why divide elastic deflection by I (asce 7-05, 12.8.6)

sandman is correct.

btw..  "horizontal" deflections are usually referred to as "Drift" (I got  bit confused when I read the title of your post)

RE: Why divide elastic deflection by I (asce 7-05, 12.8.6)

Additionally, the "service" wind load doesn't change for a higher I.  It's an attempt to bump up the wind loads that the structure is designed for based on strength.   To get that back down to "real" service winds for drift, you would divide by I (it's not exact given second order effects and the like, but it's close enough).

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