Huh? What on earth are you trying to convey?
Edit: Nvm I see what you're trying to say. Was just odd wording.
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Severe WX December 10 & 11, 2021 Severe Threat
- Thread starter Richardjacks
- Start date
Edit: Nvm I see what you're trying to say. Was just odd wording.
CalebRoutt
Member
Below is a few photos I took from Dawson Springs. The damage was utterly terrible and without question would’ve been rated EF5 had there been better construction practices. The debris granulation/wind rowing was horrific.
Attachments
tornado examiner
Member
still should have been rated EF5....but...you know...nws paducah...
Sawmaster
Member
Warning: This may be a "long-track" post, a confirmed "wall of text" has been sighted below 
Anchor bolts or foundation straps are required in probably every major metropolitan area in the US along with maybe half of the rest population-wise. Building codes aren't Federal, but are for each State to decide, and most States leave it to the Counties and Cities therein to decide for themselves what they want to do. Within 40 miles of where I'm sitting I can count 9 places where building codes exist, and at the most 2 will be the same version of the ICBO building code. The other places have variations and additions. One County has no building codes, and if I work in NC nearby there's probably half again as many code districts to deal with. Thank God I'm semi-retired because it was absolutely crazy to keep up with in my prime years. The last new home I was involved with a couple months back had poured-in-place foundation strapping in the slab instead of bolts. I do know that most code districts here require bolts.
Another problem is inspections and enforcement. One geezer in one of my current work counties looks till he can find something to fail you on, same with one city which I refused to work in many years ago. Nobody has ever built a perfect house and nobody ever will. If a nail is 1/4" too far from the next one there's no practical difference in strength as long as it's an isolated situation and not found everywhere- that's the kind of thing I'm talking about. I've never failed an Inspection except with those two. Early in my career my main County had one inspector taking grafts; luckily he got caught and was fired, but nobody went back to re-inspect the buildings he covered. Most inspectors are common-sense guys, and as long as you are earnestly trying to build well and haven't missed or botched a code requirement will tell you what they want to see next time and will let minor violations slide. Or they'll tell you to fix something and how to do it, then sign you off. Some inspections are framing only, some are "3 in 1" where they want plumbing and electrical roughed in before they come out. Some have construction experience and some don't. None I've encountered would let a substantial violation go such as no washers or nuts on foundation bolts or roofing members without the appropriate ties, but I'm sure that happens in some places simply because of how fragmented the whole system is here in the US.
Another problem is in the exact wording of the codes, which allows you to bolt down the sill plate under the joists and bands, then nail the band to the plate, and nail the walls on top of the decking over that. You've met the letter of the code- the structure is bolted firmly to the foundation. You can cast your anchor bolts into the cells of a concrete block stem wall and it meets most codes, and we all know how poorly that performs, but again it's code-legal. With slab homes the bolts go into the bottom wall plate because that's all that is there to bolt into, and now you've met the letter and intent of the codes, and those do perform well. The type of construction also varies; engineered floors using "IJT" panel trusses for floors have an odd height not matched by common lumber sizes, so those use a engineered OSB band to match, and that band does not retain fasteners as well as lumber, plus toe-nailing it (which is the only way to hold it in place without strapping) tends to break chunks out of it rendering the connection weak. But it's code-legal in most places and since it's the most cost-efficeint method most new homes on a crawlspace or multi-story homes now use it. Only if strapping is specifically required will you see that used, and only then will you have good strength, as that allows enough fasteners to overcome the inherent weakness of the material.
On homes with the subfloor swept away we can only conjecture most of the time, but with enough vertical wind lifting it's not that tough to do, because now the wide expanse of the floor surface is what is being acted against, not just the narrow sides. And if wind gets underneath through failed fenestration or by having part of the decking compromised it will act like the roof I refereed to earlier and be pushed up, not down. Other than through-bolting to the wall plates above or with strapping can you gain a really good holding down of a subfloor, and that kind of construction is uncommon. At EF-5 level nothing is sure, and it's nearly the same at EF-4. With that kind of destruction we can't know if the subfloor was impacted by heavy solid debris at high velocity as you can't tell that from scattered wood shards. We can't know if something impacted it then blew away, compromising it's strength such as would allow the rest of it to be destroyed. What we can know is that common building techniques and practices don't utilize all the strength which that structure could offer. Much better can be done, but isn't.
As to anchor bolt diameter, you have to keep in mind that anything larger than what is needed removes more wood from the plate it goes through, thus rendering the wood weaker and more prone to split along the grain. If it's only going through one 2X4 wall plate, a 1/2" or 5/8" bolt well fitted is probably where you want to be. If it's extending unsupported through a subfloor into a wall plate, a larger diameter would better resist bending, thus making it a better choice there. Carpenters don't drill a 1/2" hole for a 1/2" bolt because it isn't easy to get perfect alignment will a row of bolts using wood that has a bend in it (as much framing wood does), and any error in placing any hole in that plate means taking it back off and fixing the problem which takes time you're not getting paid for. I've seen 5/8" and 3/4" holes bored for 1/2" bolts to make the job easier and faster. Personally I add 1/8" above the bolt size to drill. And what of the washer, is it of enough strength to not bend into a cone adding to the pressure which will split the wood along the grain? Washer diameter also plays a role here as does hole placement. Going bto a larger diameter bolt exposes more end-grain in the holes increasing the likelihood that a split will develop from the hole. Masons and concrete crews aren't going to ensure the bolts are in the exact center of the wall. I've had to bend anchor bolts over enough so that the washer didn't protrude past the edge of the wall plate to the average of maybe 3 bolts per house- more if the previous workers were sloppy as is often the case. Then there's the bolt's metallurgy which may be substandard. I've done Form Carpentry for factories and other structures where the end position of the bolt had to be +/- 1/16" and the protrusion set +/- 1/8". I know how to do that while almost no residential carpenters do. I understand why the 'legs' of the bolts holding down a column need to be turned in a specific direction for strength while most residential carpenters don't. Anchor bolting in homes is sloppy at best, but if done decently works out OK because the wood becomes the weakest part of the system. That's the point you want to arrive at without going further.
Phil
Anchor bolts or foundation straps are required in probably every major metropolitan area in the US along with maybe half of the rest population-wise. Building codes aren't Federal, but are for each State to decide, and most States leave it to the Counties and Cities therein to decide for themselves what they want to do. Within 40 miles of where I'm sitting I can count 9 places where building codes exist, and at the most 2 will be the same version of the ICBO building code. The other places have variations and additions. One County has no building codes, and if I work in NC nearby there's probably half again as many code districts to deal with. Thank God I'm semi-retired because it was absolutely crazy to keep up with in my prime years. The last new home I was involved with a couple months back had poured-in-place foundation strapping in the slab instead of bolts. I do know that most code districts here require bolts.
Another problem is inspections and enforcement. One geezer in one of my current work counties looks till he can find something to fail you on, same with one city which I refused to work in many years ago. Nobody has ever built a perfect house and nobody ever will. If a nail is 1/4" too far from the next one there's no practical difference in strength as long as it's an isolated situation and not found everywhere- that's the kind of thing I'm talking about. I've never failed an Inspection except with those two. Early in my career my main County had one inspector taking grafts; luckily he got caught and was fired, but nobody went back to re-inspect the buildings he covered. Most inspectors are common-sense guys, and as long as you are earnestly trying to build well and haven't missed or botched a code requirement will tell you what they want to see next time and will let minor violations slide. Or they'll tell you to fix something and how to do it, then sign you off. Some inspections are framing only, some are "3 in 1" where they want plumbing and electrical roughed in before they come out. Some have construction experience and some don't. None I've encountered would let a substantial violation go such as no washers or nuts on foundation bolts or roofing members without the appropriate ties, but I'm sure that happens in some places simply because of how fragmented the whole system is here in the US.
Another problem is in the exact wording of the codes, which allows you to bolt down the sill plate under the joists and bands, then nail the band to the plate, and nail the walls on top of the decking over that. You've met the letter of the code- the structure is bolted firmly to the foundation. You can cast your anchor bolts into the cells of a concrete block stem wall and it meets most codes, and we all know how poorly that performs, but again it's code-legal. With slab homes the bolts go into the bottom wall plate because that's all that is there to bolt into, and now you've met the letter and intent of the codes, and those do perform well. The type of construction also varies; engineered floors using "IJT" panel trusses for floors have an odd height not matched by common lumber sizes, so those use a engineered OSB band to match, and that band does not retain fasteners as well as lumber, plus toe-nailing it (which is the only way to hold it in place without strapping) tends to break chunks out of it rendering the connection weak. But it's code-legal in most places and since it's the most cost-efficeint method most new homes on a crawlspace or multi-story homes now use it. Only if strapping is specifically required will you see that used, and only then will you have good strength, as that allows enough fasteners to overcome the inherent weakness of the material.
On homes with the subfloor swept away we can only conjecture most of the time, but with enough vertical wind lifting it's not that tough to do, because now the wide expanse of the floor surface is what is being acted against, not just the narrow sides. And if wind gets underneath through failed fenestration or by having part of the decking compromised it will act like the roof I refereed to earlier and be pushed up, not down. Other than through-bolting to the wall plates above or with strapping can you gain a really good holding down of a subfloor, and that kind of construction is uncommon. At EF-5 level nothing is sure, and it's nearly the same at EF-4. With that kind of destruction we can't know if the subfloor was impacted by heavy solid debris at high velocity as you can't tell that from scattered wood shards. We can't know if something impacted it then blew away, compromising it's strength such as would allow the rest of it to be destroyed. What we can know is that common building techniques and practices don't utilize all the strength which that structure could offer. Much better can be done, but isn't.
As to anchor bolt diameter, you have to keep in mind that anything larger than what is needed removes more wood from the plate it goes through, thus rendering the wood weaker and more prone to split along the grain. If it's only going through one 2X4 wall plate, a 1/2" or 5/8" bolt well fitted is probably where you want to be. If it's extending unsupported through a subfloor into a wall plate, a larger diameter would better resist bending, thus making it a better choice there. Carpenters don't drill a 1/2" hole for a 1/2" bolt because it isn't easy to get perfect alignment will a row of bolts using wood that has a bend in it (as much framing wood does), and any error in placing any hole in that plate means taking it back off and fixing the problem which takes time you're not getting paid for. I've seen 5/8" and 3/4" holes bored for 1/2" bolts to make the job easier and faster. Personally I add 1/8" above the bolt size to drill. And what of the washer, is it of enough strength to not bend into a cone adding to the pressure which will split the wood along the grain? Washer diameter also plays a role here as does hole placement. Going bto a larger diameter bolt exposes more end-grain in the holes increasing the likelihood that a split will develop from the hole. Masons and concrete crews aren't going to ensure the bolts are in the exact center of the wall. I've had to bend anchor bolts over enough so that the washer didn't protrude past the edge of the wall plate to the average of maybe 3 bolts per house- more if the previous workers were sloppy as is often the case. Then there's the bolt's metallurgy which may be substandard. I've done Form Carpentry for factories and other structures where the end position of the bolt had to be +/- 1/16" and the protrusion set +/- 1/8". I know how to do that while almost no residential carpenters do. I understand why the 'legs' of the bolts holding down a column need to be turned in a specific direction for strength while most residential carpenters don't. Anchor bolting in homes is sloppy at best, but if done decently works out OK because the wood becomes the weakest part of the system. That's the point you want to arrive at without going further.
Phil
CalebRoutt
Member
You criticize the NWS too much.
tornado examiner
Member
maybe.......but at least im honest
This issue isn't honestly, the issue is knowing what you are talking about, which most of the time you don’t.
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CalebRoutt
Member
The environment on 12/10 was about as good as you can get. The shear profiles were almost the exact same as northern AL on April 27th 2011. The VAD hodograph from KPAH looked like a carbon copy of KGWX during Hackleburg. With MLCAPE valued of roughly 1500 j/kg and 0-1km SRH exceeding 400 m2s2, that was a legit spring time type of profile. Sorry but this is an easily disprovable comment.
Shakespeare 2016
Member
I think there is a case for an EF5 rating but not a strong one.
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This might be old news to some, as I haven't checked the DAT for Dec 10/11 for a while now, but I have noticed some changes to DIs. Initially thought I was going crazy and forgetting some details, but then was sure.
It looks like the NWS have added this new EF4/170mph DI near Dawson Springs
However, I have also noted the removal of DIs and photos on DIs from Mayfield, Cambridge Shores, Dawson Springs, and possibly a few more places I didn't notice. Like I said, this may be old news for you guys but it is not for me, and I just find it a bit curious, especially as some of the DIs were not marginal EF4s cases (some I remembered being 180-190mph and some photos from those are now gone. I doubt we will find a proper explanation for this unless its something more random (like they got removed and added by accident - seems a bit unlikely) but if anyone has any thoughts I would love to know.
It looks like the NWS have added this new EF4/170mph DI near Dawson Springs
However, I have also noted the removal of DIs and photos on DIs from Mayfield, Cambridge Shores, Dawson Springs, and possibly a few more places I didn't notice. Like I said, this may be old news for you guys but it is not for me, and I just find it a bit curious, especially as some of the DIs were not marginal EF4s cases (some I remembered being 180-190mph and some photos from those are now gone. I doubt we will find a proper explanation for this unless its something more random (like they got removed and added by accident - seems a bit unlikely) but if anyone has any thoughts I would love to know.
Lake Martin EF4
Member
Were any from Bremen? If so...
...I could honestly see NWS Paducah realizing they screwed up.
tornado examiner
Member
nothing in bremen has changed. and i see that nothing has changed at all for at least 2 months....the survey is definitely final which is a pain.
tornado examiner
Member
the fact that they never did fix the rating of the princeton uk research facility is mind boggling. 5 months later and they still have too different EF3 points, WITH TOO DIFFERENT WIND SPEED VALUES to represent it. one 153 mph point which is laughable and stupid, and another 165 mph point which is better but also still quite stupid as it's obvious that it's at least 190 MPH damage if not 200+...not to mention the di they used for it is most likely wrong.
Lake Martin EF4
Member
As was stated, that facility had a major structural flaw that prevented a higher rating.
tornado examiner
Member
we're never seeing an EF5 tornado ever again
SouthFLwx
Member
Honestly alot of people say that and while I see where they are coming from, I do firmly believe that the EF5 drought “has” to end at some point, if you all understand what I’m saying.
Brice Wood
Member
Yea I mean there’s only a matter of time until a tornado truly powerful enough will hit something well built at EF5+ strength.. Not being sarcastic either, all things have to come to an end.
Yeah I agree as well. Its also only a matter of time that one occurs in a WFO which is less conservative. Nearly no doubts if Vilonia had occurred in say, NWS Birmingham or NWS Norman that it would have been rated EF5, similar for Mayfield tornado, EF5 damage there was a bit less clear cut.
Lake Martin EF4
Member
Nah Norman would have found a way to downgrade it. If they were as good as, say, NWS Birmingham, May 24, 2011 would have had three simultaneous EF5's.
Especially after that statement from the surveyor at NWS Norman earlier... I wouldn't be surprised if there will eventually have been 3 EF5s on that day.
While I do agree that the 2 EF4s on May 24th were almost definitely EF5s and in my opinion the rating was not without flaw, they did rate Moore 2013 an EF5, which especially after some comments by Tim Marshall and others (can't remember the exact stuff but something about incorrect or subpar anchoring) does suggest they are not *that* 'scared' of giving EF5 ratings or whatever, and which I'm sure some other offices would have come up with excuses for, and in my opinion was a thorough and accurate survey.