dozer
Structural
- Apr 9, 2001
- 506
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.
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.
