×
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

Specification semantics

Specification semantics

Specification semantics

(OP)
Our client just revised his spec concerning wind to say the following:

Structures shall be designed per ASCE/SEI 7-10 based on the basic wind speeds (3-second gust) shown in the table below, with no importance factor and no load factor:

The table then has a wind speed for our structure that's just a bit higher than what you would get reading it off the Category III and IV map in ASCE 7-10. OK, that's fine. Let's look at the wording in italics. First of all, "no importance factor". When you tell me to use ASCE 7-10 importance factors are no longer used for wind, so you're just stating the obvious. Not sure why he felt like he had to add that little nugget but I'll give him a pass, chalking it up to over exuberance.

But I gotta draw the line at "no load factor". What does that even mean? Did he mean use a load factor of 1? That's still a load factor. Besides, the third LRFD combination in ASCE 7-10 is 1.2D + 1.6(Lr or S or R) + (L or 0.5W), so is he saying instead of using 0.5W use W?

And suppose you are going to use ASD (which we are)? I'm not sure if you call the factors in ASD "load factors" but what else would you call them? Am I supposed to use a factor of 1 on the wind load even though it's a strength level wind? My answer is, "Of course not", but the spec writer has set us up to get raked over the coals. I can see it now. "I see you multiplied the wind load by 0.6 in several combinations. We told you to not use load factors." Sorry, I thought I would use common sense instead of your dumb ass spec.

Obviously the answer is to go back to the client now and ask just what he is trying to say. I just needed to vent before I do and maybe get some perspective from you folks. I would make the plea to spec writers, just tell us what code you want us to use and don't try to repeat stuff that is already in the code. Nine times out of ten it just ends up confusing the issue.

RE: Specification semantics

I don't know why spec writers feel the need to overspecify things.

That said, I interpret their language to mean that the table has no importance factor or load factor applied and that the engineer needs to factor them appropriately.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
https://www.facebook.com/AmericanConcrete/

RE: Specification semantics

If the table has just wind speeds in it, and not pressures, then the notion of load factors is even more non-sensical and I feel your pain.

RE: Specification semantics

Be aware that if your customer googles the topic, your post above may be the #1 hit, so edit if appropriate.
A quick call could potentially save some grief.
They may just be saying "don't reduce the live load when you apply the wind" or something like that. Or maybe they are intending that ASD be used.

RE: Specification semantics

You need a clarification... for another spec revision... is this a project under bid? or has a tender been awarded... If awarded, then this should be a notice of change with an appropriate extra to contract.

Dik

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