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'[OT] Windy Gusts and buildings question.'
2011\02\07@052907 by cdb

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To the north of where I live the wind has been a bit blustery of late and it has put me in thinking mode.

1. I noticed that some (and I've seen this in the US as well) were taping the outside of their windows. I posed this question at work today (and was informed I know nothing mate), surely it would be better to tape the inside of the glass instead of the outside or preferably both sides?
My thinking is, that the wind blows from without (normally) so the strong side of the tape which is the backing is being blown to it's weakest point. When I replace cracked glass on monitors (not the lizards, they don't like that), I only have access to the outside to begin with, when I tape the outside, then remove the glass from the frame, if I push my finger into the glass it will bend, if I push against the tape there is more resistance, surely the same principle applies to house glass, even with the added fact the wind pressure from a cyclone etc would be causing different pressures within and around the building.

2. If the windows are recessed (true, unusual here) surely it would be better to put wood or similar across the opening as in a shutter to present a straight face to the oncoming wind thereby increasing the likelihood of getting a more even pressure against the dwelling?

3. Rooves get torn off partly due to unequal pressure in the building so in essence they get sucked off.  Wouldn't actually opening all your doors and windows make it more likely to have less pressure differential therefore less strain on rooves and walls and they are therefore more likely to survive? Obviously the house contents become vulnerable.

4. If houses were round in shape instead of square angles with sharp edges, wouldn't a round house present less resistance to the wind thereby causing it to dissipate or be deflected due to less surface area presented to the wind? I think the effect on the complete building would be similar to the keystone in a bridge but in a horizontal fashion so the stresses would be equal in all parts of a round building. As not everyone would be happy with a round interior, surely softening the sharp edges of a building Art Deco style might help?

I'm so convinced of my thoughts I am blind to where my theory falls down, but I'm sure many amongst you will be able to point out my failings. :)

Both my copies of the OED say I can use rooves, but you are allowed to dispute it, and consider roofs far more refained!

Colin
--


cdb,  on 7/02/2011

2011\02\07@061236 by apptech

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> 1. I noticed that some (and I've seen this in the US as well) were taping
> the outside of their windows. I posed this question at work today (and was
> informed I know nothing mate), surely it would be better to tape the
> inside
> of the glass instead of the outside or preferably both sides?

AFAIK tornados suck.
(Maybe the RAF ones do differently but they are less common overall).

I understand that openiong all windows and doors may increase tornado resistance. Probably also draftier in the interim :-).

Maybe opening all doors and windows and taping plastic sheeting in place with a minimal resistance to pressure, would approximate best of both worlds.

Force on a 2 foot x 3 foot window (olde units) with 1 psi diffrerential is about 850 lbf. Intuition says that most at-hand plastic film would leave the building before then. Intuition has been known to be wrong. Calculation may help but someone else wioll have to do it.

However, the linear peel pull on the tape around the edges (if pressure was linearly spread is about 7 lbf per inch. Some tape would hold that. It would be interesting to see where the tape peel, sheet rip crossover point was for various apertures and materials.

 Russell

2011\02\07@083641 by PICdude

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Quoting cdb <spam_OUTcolinTakeThisOuTspambtech-online.co.uk>:

> ...
> 1. I noticed that some (and I've seen this in the US as well) were taping
> the outside of their windows. I posed this question at work today (and was
> informed I know nothing mate), surely it would be better to tape the inside
> of the glass instead of the outside or preferably both sides?
>

Couple decades ago when I moved to the U.S., I learned about this  practice during hurricane season... and did it.  However, I later  questioned it and researched, and found out that the tape isn't there  to stop the window breaking, but rather to keep shards flying  everywhere if/when it does break.  Makes far more sense to me, though  I would think that that would still require far more tape to be  noticeably effective.  I really can't see a few stripes of masking  tape doing much to stop shards flying, and thinking that perhaps  window tint (would be far more effective at that).

Cheers,
-Neil.

2011\02\07@083906 by Carl Denk

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I doubt as a structural Engineer that tape will prevent the glass from cracking, but if the tape has significant tension strength, it probably will help keep large pieces of glass from departing the area, but as mentioned pealing with a zipper action could occur. There is now, a plastic film that can be either applied to the glass surface or in laminated glass like a car windshield to contain the broken glass pieces.

The several structural failure of glass and it's framing that I have been involved with. all the broken glass pieces were on the build in exterior, and aluminum framing bent toward the outside. A common failure is the fasteners of the aluminum to the building structure were not strong enough.

In building design, the corners edges of the building locally require higher design forces. A common large area wind force in a non-hurricane are is of the range 20 - 30 PSF.

On 2/7/2011 6:09 AM, apptech wrote:
{Quote hidden}

>

2011\02\07@095405 by Carl Denk

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I hadn't seen this post when writing previously. The window tint film is similar to the film I refereed to. Wind resistance of structures is a very active topic in the structural engineering/architecture community. The topic continues from just the glass that receives the load from the wind, continues to anchoring the film and or glass to the frame, the frame anchorage to the structure, and the structure able to resist the forces. Most of this is fine details, and retrofit to existing buildings is difficult. The retrofit is mainly driven by insurance companies that either will not cover or at high rates the buildings that do not meet current standards.

Building are not alone in resistance to wind damage, one of the more noted is the Kinzua railroad bridge on Pennsylvania, USA. This was once one of the longest, highest bridges in the world, in daily use, until a tornado took down (to the ground) a large part of it. It was very sad. :(
See:
www.dcnr.state.pa.us/stateparks/parks/kinzuabridge.aspx
http://www.pennsylvania-mountains-of-attractions.com/kinzua-bridge.html

> Quoting cdb<.....colinKILLspamspam@spam@btech-online.co.uk>:
> I really can't see a few stripes of masking
> tape doing much to stop shards flying, and thinking that perhaps
> window tint (would be far more effective at that).
>
> Cheers,
> -Neil.
>
>
>

2011\02\07@100836 by RussellMc

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> Building are not alone in resistance to wind damage, one of the more
> noted is the Kinzua railroad bridge on Pennsylvania, USA. This was once
> one of the longest, highest bridges in the world, in daily use, until a
> tornado took down (to the ground) a large part of it. It was very sad. :(
> See:
> www.dcnr.state.pa.us/stateparks/parks/kinzuabridge.aspx
> http://www.pennsylvania-mountains-of-attractions.com/kinzua-bridge.html

Sadly, a case of too little too late - see 'history" section on this page.
Found to be ultra rusty. Under restoration. Wind risk known. Happened ...

        http://www.dcnr.state.pa.us/stateparks/parks/kinzuabridge.aspx

Windpower ! :-(

 http://www.dcnr.state.pa.us/stateparks/parks/kinzuabridge/kinzuaphotogallery.asp

2011\02\07@113549 by Carl Denk
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Yep, too late. As a result of the I-35 Minneapolis bridge disaster, mandated bridge inspections have been required, but it took a little time for that to filter down to the actual structure. And then there is the issue of inspections and fixes cost money, and with a lack of that, can imagine where that is headed - closed bridges, bottle necks, long tortuous detours. :( To do an inspection correctly, requires competent people crawling all over the structure from divers in the water to the very highest point, measuring remaining material and condition, then doing a structural analysis  using current design criteria. The current design criteria reflects more current knowledge of the materials, usually indicates a more economical structure, but there have been a few important failure items found over the years.

Several years ago, I rode in an open car, a steam powered tourist train across the bridge, that was exciting.
> Sadly, a case of too little too late - see 'history" section on this page..
> Found to be ultra rusty. Under restoration. Wind risk known. Happened ...
>
>           http://www.dcnr.state.pa.us/stateparks/parks/kinzuabridge.aspx
>
> Windpower ! :-(
>
>    www.dcnr.state.pa.us/stateparks/parks/kinzuabridge/kinzuaphotogallery.aspx
>

2011\02\07@114738 by Michael Watterson

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On 07/02/2011 16:35, Carl Denk wrote:
> requires competent
> people crawling all over the structure from divers in the water to the
> very highest point, measuring remaining material and condition, then
> doing a structural analysis  using current design criteria.

Like the Irish rail viaduct last year or year before that was inspected and fell into sea just after train passed.

Some scouts had contacted the rail company, but no diver went down

2011\02\07@120952 by Carl Denk

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Currently, here in Ohio, it is very lucrative to be a diver that has a registered engineer's license, that also has a bridge inspection certificate. Even small bridges require inspection, but then there is the guy with a heavy load, bootlegging, driving back roads to avoid being caught with no overweight permit, and the bridge fails suddenly.

This brings me to the TV show "IRT" (Ice road truckers), where several USA drivers were in back area India near a dam construction. many of the bridges and roads were very dangerous. Apparently there are no authorities to regulate loads on the bridges, or even to post weight limits. Every state in the USA has an authority that issues oversize/overweight permits after they investigate the route and determine that clearances and weight limits are acceptable. The fines for violations are very stiff, and the load doesn't move until a permit is issued, which may take some time, or not at all.

On 2/7/2011 11:47 AM, Michael Watterson wrote:
{Quote hidden}

>

2011\02\07@122223 by alan.b.pearce

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> This brings me to the TV show "IRT" (Ice road truckers), where
> several USA drivers were in back area India near a dam
> construction. many of the bridges and roads were very dangerous.

Haven't seen a series where they do that. Just recently started a new series here in the UK, but I wouldn't mind betting that we are at least one series, probably more, behind. I think we are on the third or fourth series.

Mad enough driving over the ice where there is some sort attempt at maintaining safety by measuring the thickness - don't know that I would trust outback third world at all.
-- Scanned by iCritical.

2011\02\07@122703 by RussellMc

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> Currently, here in Ohio, it is very lucrative to be a diver that has a
> registered engineer's license, that also has a bridge inspection
> certificate. Even small bridges require inspection, but then there is
> the guy with a heavy load, bootlegging, driving back roads to avoid
> being caught with no overweight permit, and the bridge fails suddenly.

Maybe there's a place for a fail-on-overload or just trip-on-overload
wheel trap on the approaches.
Cost benefit issues, as ever.

2011\02\07@135256 by William Wilson

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________________________________________
{Quote hidden}

1. Neil had the right answer. The reason that you put tape over the windows is to
hopefully stop large shards of glass from flying around if the window breaks.  If
you have double paned windows, then you need to put it on the inside of the house too.
>From what I have seen, the larger the piece of glass shard, the more likely it is to
fly like a knife through the air. It is common to see large pieces of glass stuck over an inch
deep into 2x4s, but I can't remember ever seeing a piece smaller that about 2 square
inches stuck in anything - the smaller pieces usually just land on the floor a few feet away.
Three pieces of tape in a star pattern works nicely.

2. Wood is definitely better at protecting the windows, not only from wind but from
flying debris (tree limbs, dirt, rocks, road signs, etc.). If you are staying within the dwelling
though, it's a good idea to board and tape the windows in case a flying 2x4 blows through
the plywood.
3. Opening the doors and windows does relieve the air pressure in the dwelling; however,
it also allows all of the debris to go flying through the dwelling and do a lot of damage
and anything inside of dwelling can become a projectile.
The houses that I've seen implode due to tornados were doomed any way and I don't think
that opening the doors and windows would have helped. I've also seen drafty barns with
plenty of air leaks have their roofs ripped off too. I've also seen tornados tear through neighborhoods leaving some houses alone and destroying others. My personal feeling is that
if mother nature is out to get you then no amount of tape, boards, window opening, or whatever
is going to save you

2011\02\07@142632 by Richard Prosser

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On 8 February 2011 07:52, William Wilson <@spam@CRISKILLspamspamclemson.edu> wrote:
> ________________________________________
>>From: KILLspampiclist-bouncesKILLspamspamMIT.EDU [RemoveMEpiclist-bouncesTakeThisOuTspamMIT.EDU] On Behalf Of cdb [spamBeGonecolinspamBeGonespambtech-online.co.uk]
>>Sent: Monday, February 07, 2011 5:28 AM
>>To: TakeThisOuTPICLISTEraseMEspamspam_OUTMIT.EDU
>>Subject: [OT] Windy Gusts and buildings question.

>
> 3. Opening the doors and windows does relieve the air pressure in the dwelling; however,
> it also allows all of the debris to go flying through the dwelling and do a lot of damage
> and anything inside of dwelling can become a projectile.
> The houses that I've seen implode due to tornados were doomed any way and I don't think
> that opening the doors and windows would have helped. I've also seen drafty barns with
> plenty of air leaks have their roofs ripped off too. I've also seen tornados tear through
> neighborhoods leaving some houses alone and destroying others. My personal feeling is that
> if mother nature is out to get you then no amount of tape, boards, window opening, or whatever
> is going to save you.
> --


IIRC Mythbusters did a scale test of this & found that while opening
all doors and windows had an advantage in the ideal case, in most real
world cases there is insufficient door and window area to make much
difference. Not to mention the flying debris effect.

R

2011\02\07@143020 by cdb

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:: AFAIK tornados suck.
,
Aha, the flaw, or one of, in my thinking. I was concentrating on the prior and post wind gusts, not the actual rotational consequences.

Though of course like a vacuum cleaner, what sucks at one end must blow out another.

Colin --
cdb, RemoveMEcolinspamTakeThisOuTbtech-online.co.uk on 8/02/2011
Web presence: http://www.btech-online.co.uk   Hosted by:  http://www.justhost.com.au
 

2011\02\07@144420 by cdb

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I see.

So would a round house or rectalinear with rounded corners be more stable than traditional box shapes? Even those rare wavey shaped houses?

Colin
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cdb, colinEraseMEspam.....btech-online.co.uk on 8/02/2011
Web presence: http://www.btech-online.co.uk   Hosted by:  http://www.justhost.com.au
 

2011\02\07@152618 by Carl Denk

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Basic aerodynamics is, greatest force would be a flat plate perpendicular to the air flow, and round would be less. Other than that it becomes complicated, with ratio of sides, skin friction, and other factors. On a sloped roof, the windward side is inward pressure, and lee side outward, but edges (eaves and ridge) cause turbulence.

On 2/7/2011 2:44 PM, cdb wrote:
> I see.
>
> So would a round house or rectalinear with rounded corners be more stable
> than traditional box shapes? Even those rare wavey shaped houses?
>
> Colin
> --
> cdb, EraseMEcolinspambtech-online.co.uk on 8/02/2011
>
> Web presence: http://www.btech-online.co.uk
>
> Hosted by:  http://www.justhost.com.au
>
>
>
>
>
>
>

2011\02\07@164936 by IVP

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> the tape isn't there to stop the window breaking, but rather to
> keep shards flying  everywhere if/when it does break

Yes. Very common to see windows crossed with tape, in
London during The Blitz for example. My guess is that paper
tape would have been the only widely available type and I
wonder how effective it would have been. Paper tape might
have a bit of tensile strength but it tears easily

If a 500kg spengbombe landed between the kitchen and the
outside carzey, my money's on the bomb

Not the final authorities, sometimes not even close, but ....

Windows open/closed

http://mythbustersresults.com/hurricane-windows

and as a side dish

http://mythbustersresults.com/curving-bullet

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