Jump to content

Normandy

Members
 View Profile  See their activity

  • Posts

    820

  • Joined

  • Last visited

 Content Type 

Posts posted by Normandy

    Dec. 10-11 Severe Weather

    in Lakes/Ohio Valley

    Posted

    1 hour ago, Buckeye05 said:

    To be fair, metal warehouse buildings tend to "catch" wind due their lack of interior walls, sharp angles, and wide, flat surface areas, which act as a sail once wind enters the building. Once that happens, the metal exterior sheeting comes off, and the entire metal frame of the building warps, twists, and sometimes causes the overhead metal framing to collapse like dominos. There's a big difference between a metal-framed warehouse building and a metal-framed institutional building, and while the scale is indeed flawed, these two structure types are listed as separate DIs for good reason. Next time there's an EF2 or EF3 in a populated area, compare the damage to metal warehouses along the path to other structures with different construction methods. You'll see that the metal buildings always end up being mangled quite badly, while others nearby may only sustain roof loss. I've seen EF2s move through neighborhood and cause moderate to heavy damage to frame homes, but not totally destroy them, then essentially demolish a metal warehouse in the immediate vicinity. This is no fluke. Truly violent metal warehouse damage only really occurs when the metal support beams themselves are sheared off at their anchor plates, and the entire framing system is pushed or twisted off the foundation. I don't see anything like that in the above photo. To find damage like that, you have to look at events like Parkersburg, Guin, Van Wert, and most infamously Niles/Wheatland.

    I disagree.  Warehouses like this actually do the opposite as what you are stating.  The lack of interior bearing walls, methods of roofing attachment, and methods of exterior wall attachment of warehouse buildings means that a violent tornado is likely to remove the building skin and roof within second.  It would be akin to peeling off a sheet of paper, leaving the structural frame completely exposed.  Once the structural system is completely exposed, there is no "wind catching" whatsoever.  The deformation you are seeing is the winds deforming the structural system with whatever PSF is required to deform the steel.  In general this is 35,000 PSI of force, which is produced by 306 MPH winds.  

    Lets clarify removal of anchor plates as well.  Anchor plates are the means by which steel columns transfer load to the foundation structure.  Steel beams are connected to said columns using moment connections or fixed bolted connections.  In this case because seismic is not a concern, fixed bolted connections are likely being used.  If a steel frame, which acts as one rigid body, is being deformed to the point of collapse.....you can bet an EF-5 is the culprit.  Winds below 200 mph are simply not enough to mangle a low-story, wide base steel structure that has beams up to 2'-0" deep.  Focus on the structural system, not the overall building damage. 

     

    Wind catching is more of what you are seeing here:  Where a structure is so tall that the wind exerts large amount of force on the upper half of a structure that the mid point deforms.  In this case, it absolutely does NOT take 35,000 PSI to deform the steel because there is additional force being generated by the top heavy structure moving laterally.

    https://www.columbian.com/news/2017/feb/20/storms-damage-san-antonio-area/

     

    EDIT:

    Here is a great video that illustrates how insane it is that a steel structure can be deformed to the point of collapse by winds.  This is our famous gas station video of hurricane charley.  it is widely assumed that winds in this video reached somewhere between 140 - 150 mph sustained.  That is well below the EF-5 threshold obviously, and notice what happens to the steel frame:  Nothing.  The same kind of process happens when a tornado hits a warehouse building.  The skin is shredded leaving the structure exposed.  Whether that structure gets deformed further depends on the wind / PSF generated.  Here it was below the threshold to bend steel.  In Mayfield it clearly was not.

     

    • Like 2

    Dec. 10-11 Severe Weather

    in Lakes/Ohio Valley

    Posted

    if you want photographic evidence of EF5 damage, look no further than the candle factory.  We have an entire steel frame that has been bent and deformed to the point that the steel Columns holding the steel beams collapsed.  steel deformation / bending occurs after 35,000 PSI (or 247 PSF). It takes 306 mph winds to produce 247 PSF.  And yet we are looking at slabbed homes and determining the structures aren’t well built?  As I said before, these folks have no clue what they are looking at and it really is unfortunate.

    FDD9600F-0CF7-48F0-A99D-E97361EA4A36.webp

    • Like 1

    Dec. 10-11 Severe Weather

    in Lakes/Ohio Valley

    Posted

    Even that example there is not nearly enough information to say an outrageous statement that there are “no connections”. The entire building is gone.  The only thing I can even begin to deduce is it was a wood frame house, with wood framed floors, built on CMU walls with a Crawl space beneath.  And even that assumption is guesswork with no other elements to review.

    • Like 1

    Dec. 10-11 Severe Weather

    in Lakes/Ohio Valley

    Posted

    Just now, Chicago Storm said:

     

     

     


    .

     

     

     

    More nonsense.  That is a standard wood stud framed single family home with brick veneer facing.  It has standard anchorage to the slab as seen by the bolts sticking out of the base stud.  The brick is completely non-structural and can actually be removed by winds lower than 100 mph.  The wood framed building cannot be removed by winds that low, and that is fairly obvious.  They have no clue what they are looking at if they think an EF-2 tornado did that.

    Dec. 10-11 Severe Weather

    in Lakes/Ohio Valley

    Posted

    Even the fact that a preliminary analysis of this turns out an EF-4 designation is very problematic.  There are several obvious indicators that this was as strong as other tornadoes that have been given both the EF-5 and F-5 designation.  Stating that there is a lack of "well-built" structures that have been swept away with only slabs remaining as a justification of not finding EF-5 damage is absurd.  As an architect this frustrates me because how is anybody defining what "well-built" means, and more importantly:  How can you determine if something was well-built if the entire damn structure is gone?  People can say "Well look at the anchorage".  There is no building code that requires a structure have anchorage that can survive 200 mph winds.  From an engineering standpoint is isn't feasible with wood frame buildings (never mind the fact that the 200 MPH winds are throwing cars, trucks, etc at high velocities that impact the structure).  

    I cannot emphasize this enough:  A building is only as "well-built" as the local building codes dictate.  The definition of "well-built" should not be determined by the ability to partially survive a 200 MPH tornado.  Building codes do change often times, and are usually caused by natural disasters.  However I can pretty much guarantee that building codes in tornado alley do not have provisions like those in other natural disaster afflicted areas (hurricane zones, seismic zones, etc).  And even if they have it is a moot point because the damage assessment requirements are extremely vague.

    The EF scale is so flawed on so many levels that its hard to even use it as a scientific tool.  How can the El Reno tornado be an EF-3 when 300 mph winds were measured by DOW? How can the Jarrell tornado be an EF-5 based on damage alone when it was moving 10 mph (as opposed to other faster moving EF-5's like this one who did the same damage)?  How are we simply ignoring other factors like defoliation, trees being debarked, ground scouring, etc? 

    Damage should never be the be all, end all factor in determining tornadic windspeeds:  because we have no earthly idea why tornadic windspeeds do the damage they do.  And I present the picture below as evidence.  Nobody who is assessing damage can sit in front of me and tell me with a straight face that this tornado did not have 200 mph winds because of poorly built structures when we have a damn bookshelf with books untouched while the entire rest of the house is completely gone.  Its all completely absurd and incredibly unscientific. 

    c2e6eb49f170e7736759cc3cad509735.webp.50bad17771474fb1eebca2b9509a7ef0.webp

     

    • Like 7

    Major Hurricane Sam

    in Tropical Headquarters

    Posted

    The latest GFS now develops a second low north of the first one ahead of Sam.  Leaves the first cut-off low behind and recurves Sam and the second together.  Unsure how plausible this is, why would the second low develop?  Would like to hear from a met

    Major Hurricane Sam

    in Tropical Headquarters

    Posted

    The CMC solution is definitely plausible, as all models have the same players on the field.  The CMC is just further west and faster, thus allowing the ridge to become more of a blocking ridge and encouraging the phase.  Is it the most likely?  Probably not.

    • Like 1
    • Thanks 1

    Major Hurricane Sam

    in Tropical Headquarters

    Posted

    14 minutes ago, OSUmetstud said:

    Every single member of the eps didn't make landfall. I'm not surprised that Eric compared a single op run to a hugo plot...and the storm still missed...

    Most of the guidance has the trough sitting on the east coast not cutting off that far southwest...and a trough in the position makes sense with a massive ridge over Ontario. 

     

    Appreciate the input.  Lets see what the subsequent model cycles show

    Major Hurricane Sam

    in Tropical Headquarters

    Posted

    19 minutes ago, OSUmetstud said:

    500mb is just all wrong for a US landfall. Theres a trough where you'd want a ridge and a ridge where'd you want a trough. So much has to change for it to happen. I'd put it at less than 10 percent...and that might be generous. 

    Can you explain this a little more?  That's not how I am reading this and want to be schooled on how I am interpreting this.  See tweet below for what I am seeing:

    https://twitter.com/andretrotter/status/1441137766515937280?ref_src=twsrc^tfw|twcamp^tweetembed|twterm^1441137766515937280|twgr^|twcon^s1_c10&ref_url=http%3A%2F%2Fstorm2k.org%2Fphpbb2%2FEmbedTweet.html1441137766515937280

    Major Hurricane Sam

    in Tropical Headquarters

    Posted

    Going to be very close if the Euro pans out.  Cut-Off Low to the west with a ridge to the east implies a due north track after the run.  Which of the two features becomes the dominant steering element likely dictates whether or not landfall occurs on the East Coast.  Stronger low seems like it would send it more west, stronger ridge seems like it would send it slowly north before ejecting NE when the next trough comes in.  On the next cycle!

    Major Hurricane Ida

    in Tropical Headquarters

    Posted

    Instantaneous gust or not that still a ridiculous observation.  And what exactly is the definition of instantaneous (1-second long?)? I don't know why but since you claimed you saw stronger winds than Josh did in Dorian I always view your posts as angling to keep Michael greater than "x".

    • Confused 1
×
×
  • Create New...