Flying Roof 1

[SteelPE]

I'm guessing they didn't have many hold downs:

https://www.youtube.com/watch?v=45SBT-2zXus

 

[BridgeSmith]

They probably had as many as were thought to be needed. Massachusetts isn't exactly in 'tornado alley', so those wind speeds likely weren't anticipated.

 

[SteelPE]

Massachusetts may not be 'tornado alley' but it does get hit by hurricanes (particularity Cape Cod), and the wind speed didn't seem excessive in the video (trees in the background bouncing back and forth).

 

[electricpete]

here's the text under the video. apparently they think it's a tornado. it didn't look like one to me, but they may know a lot more than me.

A tornado touched down on Cape Cod Tuesday. This is amazing video of the moment the roof being ripped off the Cape Sands Inn in West Yarmouth, Massachusetts

=====================================
(2B)+(2B)' ?

 

[azcats]

Some photos here. [URL unfurl="true"]https://www.masslive.com/capecod/2019/07/cape-sands-inn-in-yarmouth-will-close-for-at-least-5-week-after-tornado-damage-assessment-led-to-discovery-of-asbestos.html[/url]

Certainly wasn't much uplift restraint in the post construction.

Image 1

Can get some idea of how it was framed here. [URL unfurl="true"]https://www.bostonglobe.com/2019/07/24/see-aerial-photos-damage-from-tornados-cape-cod/8ApDale2lBYYWToiWklRML/story.html[/url]

 

[BridgeSmith]

According to the story in azcats' link, the tornadoes reached 110 mph wind speeds, which is an EF-1 tornado, but the upper end of Category 2 for a hurricane. Not as much of a difference in wind speeds as I was thinking (when someone says "tornado", I think of 150-200mph wind speeds) so yeah, having that roof come off in a 110 mph wind probably means it wouldn't have survived the next hurricane anyway.

 

[3DDave]

Hurricane winds tend to more straight-line/level. Tornadoes pull air from the ground upwards, so the effect of uplift is exaggerated. I think most people have seen the movie. I suspect it's the vertical gradient to air pressure that does the damage as opposed to the dynamic pressure of the wind.

 

[charliealphabravo]

Agree that there was not much restraint. It looks like the roof rafters were supported along the edge of the balcony by an upset rim joist attached by a few nails through the 2x plates you see in @azcats photo. The open balcony would have increased the uplift pressures. Also if the balcony ceiling was vented or open then it provided a location for the wind to get under the roof.

 

[SteelPE]

I don't know exactly how these correlate, but the current design wind speed for that area is Vult = 140 mph (Vasd = 108mph). The oldest version of the code I have here only goes to 1997 and has an allowable wind speed of 90 mph. I'm pretty sure this building predates that code. Older versions of the code can be found here:

https://www.mass.gov/service-details/past-editions-of-the-ma-state-building-code

There are some comments that the roof is new, however, I highly doubt the structure is new. The current MA building code excludes chapter 34 of the IBC and requires compliance with the IEBC. If one were to follow Chapter 4 of the IEBC it's possible that the roof structure is original. The roof was likely just replaced (new roofing materials and not structure) and not strengthened.

I would like to think a new structure would have withstood the wind loads imposed on it....and in fact, the rest of the hotel is still in place, so maybe is was just a freak issue.

Interesting enough, I was talking to a ME the other day (my neighbor has a son-in-law who is a ME). I was trying to help him fix the neighbors lawnmower. He knows I'm a licensed engineer working in the realm of structures. He proceeded to bash the SE field talking about how poorly buildings are designed/constructed today as opposed to 40 years ago. His evidence revolved around new buildings in FL that being destroyed by hurricanes. I have no idea if his examples are real or fake.... probably hearsay.... at that point I was just singing the meow mix song in my head.

 

[BridgeSmith]

There was crap construction in Florida 40 years ago, too. Most of the junk blew down or got washed away, so what's left from that era was the stuff that was built right. 40 years ago they were also cautious about building in areas affected by storm surges without accounting for that in the design; today not so much.

 

How much would it cost to improve the roof attachments?

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[SteelPE]

HotRod,

I didn't want to get into that with him. He was of the opinion that he was right and there was no convincing him otherwise.

ironic,

That depends on when you are trying to add them. If they have the underside of the roof exposed the additional costs would be less than if the existing roof was covered with gypsum. A typical roofing replacement would just have you stripping the existing roofing material off the roof and reinstalling a new material. The hold downs in question are not that expensive (as far as I know). Most of the costs is associated with the labor required for the install.

 

[azcats]

That building could have been built in the 40s or 50s.

I didn't seen a single framing connector other than nails in any photos. The joist that blew off cantilevered out over the balcony and spanned back to a perpendicular joist. It appeared that there was 3-4 nails from the perp. joist into the ends of the cantilevering joist.

 

[BridgeSmith]

3DDave may have hit on why it (presumably) has survived hurricanes, but didn't survive the tornado. The failure appears to have begun at the front edge, where there is no wall to block the vertical (uplifting) wind from hitting the underside of the balcony roof.

 

[debodine]

Since construction in Florida has been noted a couple of times in the posts, I will share a story from about 50 years ago. I must caveat that this story was related to me by a colleague with whom I worked in Ohio and is not my personal story. Although I found him trustworthy in his other communications with me, I was not present for this story and cannot vouch for the truth or accuracy of what I was told. Feel free to dismiss it as you see fit.

According to my friend, before he entered the USAF he worked as a helper in Florida residential construction. I do not know what region of Florida exactly, but the general area was central Florida because that is where he told me he grew up.

On the job of building foundations for slab-style homes, there was a requirement for inserting a rebar grid into the forms before pouring the concrete. The crew (including my friend) would wrestle the rebar into place. The job foreman would walk over to the forms with the inspector and the inspector would verify the rebar was in place. Then the foreman and the inspector would wander off a good ways, usually into the site trailer or at least behind it. Then the work crew would remove the rebar from the first foundation, move it to the second foundation, and set it in place as the concrete was being poured into the first foundation that was now without rebar.

After the first foundation concrete pour was complete, then the only person on the work crew who had permission to speak to the foreman (when the inspector was onsite) would approach the foreman with the announcement that the second foundation was ready for inspection. The foreman and the inspector would stop by the second foundation where the inspector would agree the rebar was in place. Then the foreman and inspector would wander off again, while the work crew moved the rebar to the third foundation and then the second foundation concrete pour was accomplished. Rinse and repeat for the length of the block.

 

[drawoh]

debodine,

What are the labour costs for removing installed re-bar?

--
JHG

 

[charliealphabravo]

In those days, and maybe still today, cheap immigrant labor in South Florida was a thing. Cash. Off the books. USD straight to Mexico. I've heard the same and similar stories.

 

[MacGyverS2000]

Yeah, I'm trying to image a couple of guys lugging a large framework of heavy rebar from site to site... sounds a bit... fishy.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[charliealphabravo]

I don't know why I'm pushing this narrative along since I have no evidence either but we are talking residential foundation construction. That means 2 No. 5 rebar thrown into a shallow trench.

Edit: For what it's worth, these kinds of things were happening all the way up through the Hurricane Andrew rebuild. The urban legends I heard about were things like plywood sheathing only 4 fasteners.

Edit Edit: A quick Google search brought up some interesting stories about the deficiencies exposed by Hurricane Andrew and fraudulent practices which continued on in the rebuild.

 

[BridgeSmith]

They had a few of those sheathing issues with some new houses in Minnesota when I was there about 20 years ago. Some houses lost whole sheets of roof sheathing in a 60mph wind, because the guy with the nail gun wasn't paying attention to where the rafters were that the sheathing was supposed to be nailed to, and 90% of the nails hit nothing but air.