EXPERT HURRICANE ENGINEER SCORECARD – WHAT I GOT RIGHT AND WRONG WITH HURRICANE IRMA
How did my damage predictions do?
I lived through Irma on the east coast of Florida. I watched the warnings, the preparation, and the events as they unfolded. Wind gusts in my area of Boca Raton approached 90mph.
I had long predicted what +-90mph winds would do to a neighborhood like mine, as I have predicted what stronger winds would do to areas like that of ours and Naples. This storm gave me the ability to check in with those predictions and see how the 10+ years of warnings from an expert hurricane engineer heeded since Hurricane Wilma:
Prediction #1: A lot of trees are going down
It’s the trees in wind storms like Hurricane Irma blew on the east coast of Florida that cause the damage – to powerlines, roads, houses, and our lives. The longer between storms, the more susceptible trees are to falling. And another storm blowing wind in another direction will take a whole other set of trees down.
Prediction #2: The first thing that’s going to go are all those traffic cameras on intersections
Result: Completely wrong
Seriously, every time I pull up to an intersection with those cameras all these years I would look at the connections and think they are all going to fall over. We recently calculated the forces on small wifi antennas on lifeguard stands in Miami and the bolts needed to secure those things were extreme. So far not a single camera I’ve come across was knocked out of alignment worth mentioning. Even the traffic signals were tossed around. Who knew?
Prediction #3: Awning fabric needs to be removed from the frames or they are going to blow away.
Result: Mostly true
It depends on the wind direction and other forces as I described in my other blog. Irma’s winds head on from the south as Irma blew in Boca Raton did catch awnings that were prime to blow away like the first photo below.
Others who removed the fabric as you are supposed to did much better as the similar awning as in the second photo below, both facing the same direction. Some awnings like the third photo below suffered a recognizable fate even when securely fastened down- rips, pulls, and fraying.
Prediction #4: Plywood from people boarding windows that don’t know what they are doing will be flying everywhere.
Result: Wrong (in our area)
A team of storm experts along with myself have been studying the effects of wind pressure on plywood for years. We’ve even performed multiple tests in the lab and watched plywood rip away from the Tapcon screws holding them, even in applications that the building code allows. The photo below is an image from one of those tests where the wet plywood pulled away from the anchor at an extremely low pressure, less than that which was felt in our area for Irma. And we really screwed that plywood in, more than many did during Irma
I’ve also run the calculations on plywood screwed in on building corners where the wind catches it and the wind gusts felt in Boca Raton were enough to have seen more plywood becoming flying debris. I know other areas had more damage and plywood did fly around, but I always advise against plywood for so many reasons and urge those asking to get impact glass or a code compliant impact protection system.
Prediction #5: Signs and fences are going to lean (but we design them that way)
Result: True but way less than Wilma
Maybe it’s because engineers are designing them better, maybe it’s because Wilma’s winds in our area were arguably stronger, but the combination of saturated, wet soil and strong winds will lean signs and fences over. Engineers don’t consider that a failure though. Economically, it’s more cost efficient to design signs and fences to lean over but not become flying debris than make them all so strong that nobody can afford one. The building code even allows us to design them to a lesser force than buildings for this reason.
I did see a few failures that shouldn’t have happened and a few that we know will happen that engineers don’t entirely agree with, but these are easy predictions for wind experts.
Photo 1 below is a total failure and shouldn’t have happened. The sign can lean but shouldn’t have come apart. In stronger winds the main frame top part of the sign could have become flying debris. (another example is the awning photo above, the sign components above blew off, something that shouldn’t have happened with the strength of wind in that area).
Photo 2 Below is actually a ‘pass’ for engineers – the sign stood up as expected but the sign parts flew off, something we want to happen to protect the sign structure but become flying debris and could be hazardous. That’s why you need shutters or impact windows and should not be outside during a storm.
Tree limbs and pieces like signs all fly around and are very hazardous but don’t directly affect the safety of those hunkering down in impact protected primary structures.
Photo 3 shows a fence that while leaning, did not pose a hazard and considered a properly designed component.
Prediction #6: even buildings designed under the latest codes are not designed to the latest codes until finished and can be an extreme hazard while under construction during a storm
Result: Very True
I specifically drove by this CVS under construction in north Deerfield and just knew that wall would blow over during Hurricane Irma. Sure enough, when I drove by it on the way back to work it had fallen over. Message: be very careful near construction areas during hurricanes, they are vary hazardous.
And last but not least, my favorite prediction that has always and will always come true during hurricanes: people will still use duct tape and do very stupid things to protect their houses.
Even with all the education and messages out there, people still don’t understand taping their windows does nothing at all to protect your windows. Please don’t consider yourself safer in the least bit if you tape your windows. The only benefit is that after the storm is over and your house is destroyed, the cleanup will be that much less when you can pick many broken glass pieces up with one piece of tape.
I’ve seen this in every storm since Andrew, it’s entirely false. Just google it, there’s plenty out there to warn against it. There’s even a federally funded campaign to stop this dangerous rumor to tape your windows – Go Tapeless
Worse yet are the stupid things people do to protect their glazed openings. Just look at the second photo below! The holiday decorations should be a giveaway that someone isn’t on top of their game there. I’m not even going to explain how ridiculous that method of storm protection is.