This may be more rant than anything – I don’t know. I’m curious if any of the rest of you get tired of all the code changes that affect what we do. Particularly the ones that make no sense.
One of the things that bugs me is that they’re now saying that we have to design trusses for wind loads. SIXTEEN different load cases for wind. (In addition to the usual gravity loads)
So what does the wind loading do to the trusses? In the vast majority of cases, virtually nothing. When you print out shop drawings they show a maximum uplift force at each bearing location.
Then they came up with a 10PSF non-concurrent live load for the bottom chord. You run this one with no live (snow) load on the top chord.
One engineer told me the 10 PSF was for things that people might store in the attic. So I asked – Then why only run it WITHOUT the snow load? Don’t people store stuff in their attics during the winter too? I didn’t really get an answer to that one.
Who the hell dreams this stuff up?
BTW – All of the above is for residential construction only. With commercial buildings we don’t have to do the non-concurrent live load on the bottom chord. Instead we have to design them with UNBALANCED loads.
Why design differently for commercial buildings? Does the snow fall differently on them?
Once they start adopting TPI 1-2002 around here, dead loads will have to be adjusted for the roof slope. Like things weren’t complicated enough already?
I sometimes wonder why they keep making truss design more and more complicated, but don’t seem to mess with stick framing at all. Is there anywhere out there where you have to design stick framing for wind loads?
We were just getting software and computers that are fast enough to design a simple truss in a second or less. Now it takes up to 10 seconds to design the same truss, and it comes out virtually the same in the end. That really annoys me.
I don’t like wsting time. And it seems to me that all this is nothing but a gigantic waste.
Sorry for the rant. But I’m curious what the rest of you think about stuff like this…
Do they ever shut up on your planet?
Replies
I agree with you 100% I'm in a marginal area so far a live-dead load, with this new change the way it sounds to me I'll probably have to put 2 cripple studs under each end of my headers even the 18" bathroom windows. I put 2 under each side of an opening 5' or larger now. I wonder how far this extra 10 lbs is going to affect the way houses are framed in this area, headers, amount of cripples, floor joist size and so on. Thanks for the heads up Boss.
"I wonder how far this extra 10 lbs is going to affect the way houses are framed in this area..."
The 10 PSF live load is non-concurrent - Meaning you consider it as a separate load case, with no live load on the roof.
So it shouldn't affect your header designs at all.
If they start enforcing the dead load along the slope thing, that will make a differnce on higher sloped roofs.
Which is harder - to make education entertaining or entertainment educational?
Thanks for the clarification Boss, keep us posted if this actually comes into play with the higher sloped roofs, I'd hate to tear out a whole house full of headers.
"... keep us posted if this actually comes into play with the higher sloped roofs..."
It's already been written - It's just a matter of time before it gets adopted.
Codes are updated slowly, and I don't completely understand how the whole process works. (If someone here does, please tell us)
But when TPI 1-2002 is adopted by your code body you'll be subject to it. I don't THINK it's been adopted by IBC yet. St. Louis has adopted IBC, which is what pushed us over into the wind load and non-concurrent load things.
If I learn anything else on the subject I'll post about it...
There is no idea so good that everyone benefits.
"In the vast majority of cases, virtually nothing."
Correct engineering is only important in a minority of cases.
Most engineers skip the unimportant math and get to the correct math fairly fast. I guess your software does not.
Once again you have come up with a pointless and meaningless post. You claim to be an engineer, but have shown repeatedly that you have no practical knowledge of the subject. So how about coming up with something intelligent, or go away?
Are you always an idiot, or just when I'm around?
It is clear why you are not an engineer.
As they say, a little knowledge can be a dangerous thing.I have run into experienced paralegals who think they are as knowledgeable about the law as lawyers, and nurses who think they know as much as doctors, etc, but fortunately, that state of mis-understanding is rare in those fields.Too bad it is all too common in the construction industry.FYI, based on his many messages here, it seems that BH runs a computer program which designs trusses.
View Image
Sojourners: Christians for Justice and Peace
Once again Bob proves he has something to add to any discussion.
Many years of lawyering make him an expert.......
Joe H
>>Once again Bob proves he has something to add to any discussion.
>>Many years of lawyering make him an expert.......Gosh, I'm sorry.Was there something in my message you disagreed with? Did I get something wrong?And could you please tell me where I was asserting "expertise" in the message you responded to? I so much want to conform to your views and opinions.I though I was just expressing my experience, not my expertise....QUOTE
As they say, a little knowledge can be a dangerous thing.I have run into experienced paralegals who think they are as knowledgeable about the law as lawyers, and nurses who think they know as much as doctors, etc, but fortunately, that state of mis-understanding is rare in those fields.Too bad it is all too common in the construction industry.FYI, based on his many messages here, it seems that BH runs a computer program which designs trusses.
END QUOTE
View Image
Sojourners: Christians for Justice and Peace
FYI, based on his many messages here, it seems that BH runs a computer program which designs trusses.From his many posts over the years, it's my opinion that the Boss does more just "run a computer program that designs trusses."
QUOTEAs they say, a little knowledge can be a dangerous thing.
That you can't tell the difference doesn't surprise me, you're a lawyer.
Joe H
>>you're a lawyer.Nope. I used to be.
View Image
Sojourners: Christians for Justice and Peace
>>From his many posts over the years, it's my opinion that the Boss does more just "run a computer program that designs trusses."Perhaps he is: we're talking about impressions we have formed, not objective fact, of course.May I ask: is it also your opinion from reading his posts that his level of knowledge is such that he knows sufficiently more than an engineer to reliably tell the engineer he doesn't know what he is talking about?And I'm still wondering (i) what I got wrong in the message I posted and (ii) what "expertise" it was that you thought I had conveyed.In my experience (and in this case, that experience includes having studied a difficult subject 3 years, been graduated with a pretty decent GPA, been rigorously tested and licensed, been trained in the "big leagues," and practiced in an area involving billions of dollars, which practice mainly involved giving informed opinions) I have come to believe that it is easy to lash out at someone you disagree with, of course, but it might actually impresses someone if you can back it up with facts.So, any facts to support the views you hurled at me?
View Image
Sojourners: Christians for Justice and Peace
Why do you hang out here?The vast majority of us come here to learn, and to share what we know about our own specialties with other people. You do nothing but criticise others and pat yourself on the back. I may not have an engineering degree. But I know a heck of a lot more about truss design than most engineers do.And you've never spoken intelligently anough about anything to give me any reason to believe you even ARE an engineer.
Deja Moo: The feeling that you've heard this bull before.
Lemme toss this one at ya ;
I dont think this has anything to do with an engineer. Your problem I mean.
In my area the building inspector has full power at code compliance.
In the machanical fields there are state inspectors and boards of review.
An engineer is not a trump card over a BI .
An engineer or an archy normally is employed by a private party where as the BI is not suppoed to be biased one way or another .
The way to change a building code is addressing the assn. , but the BI `s ruling stands unless he wavers on his own.
I would address the BI and then if you are not satisfied , the assn.
I would want a copy of the code too and if its not found there then ask if theres local adoption of an ordinace .
Tim
Edited 2/18/2006 12:13 am by Mooney
"Correct engineering is only important in a minority of cases."
Great sign for the front door of an engineering office.
> Correct engineering is only important in a minority of cases."
Hmmm -- I can't really agree with that. But what may have been the idea here is that engineering for seismic and wind loads is kinda like seat belts in a car, and ground rods. Something unusual and bad has to happen in order to put such things to the test of the real world conditions they're designed for. It's only under those rare circumstances that you really find out if they're adequate.
Come to think of it, a couple years ago there was an earthquake in Iran that destroyed the famous brick fortress of Bam. That building was just fine for something like 2500 years. But without a seismic retrofit, it's gone now.
Bottom line, I think it is important to get those things right, even if it's extremely rare to actually need them.
-- J.S.
The reason for switching to the IBC was to make everything easier. Apparently someone realized this and felt it was too easy.
now watch the next IBC publication nullify the requirements for this one . . .
It was explained to me that the 10 psf on the bottom chord was more for construction loading (climbing on it during install), which would explain why it's non-concurrent.
"It was explained to me that the 10 psf on the bottom chord was more for construction loading..."
That may well be the case - I don't know. But that makes more sense than attic storage loading.
But - Has this seriously been a problem? Trusses failing from people walking on them?
The only cases I've heard of where this has been a concern was if there were huge knots in the bottom chord, or if the truss was broken during handling. Neither one of those situations will be addresses by adding load cases.
So it seems to be it only complicates things and accomplishes nothing.
Looking at you is like looking at a beautiful Hawaiian sunset.
But without the retinal damage.
I'm with you Boss! I've had that same beef for thirty years and the house built 50 years ago are still standing as firm as the new ones.
We have to put hurricane clips on trusses but not rafters....and the clips are holding onto a plate that is held on by foam!!!!!
Silly.
blue
"We have to put hurricane clips on trusses but not rafters"
That's part of what annoys me. Why are trusses questioned so much when stick framing isn't?
"and the clips are holding onto a plate that is held on by foam!!!!!"
That also annoys me. Why design the trusses for wind loads if you aren't going to tie them to the structure?
Stupidity got us into this mess, and stupidity will get us out. [Homer Simpson]
I don't like wsting time.
Sorry for the rant. But I'm curious what the rest of you think about stuff like this...
Boss, does BT time count as wasted?
Joe H
What do I think? They write the rules, they change the rules, they enforce some of the rules & skip the rest. Then the new guy comes along and tells me I didn't do it right, even though I did it the way the old guy wanted it done. What do I think? Don't know. Go figure.
"does BT time count as wasted?"
Uhhhhmmmmm.... That's different.
And just as soon as I figure out why I'll come back and let you know.
(-:
In this world, there are two kinds of people: Those who Get It and those who Don't. If the meaning of this is not immediately obvious to you, count yourself as one of the latter.
"Research"
Joe H
Boss, does BT time count as wasted?
Roar!
This is just another part of the "Truss Engineers Employment Security Program" (T2ESP). Remember when we could build our own trusses on site?
Beat it to fit / Paint it to match