[TECH] 3 Questions for N-gin-neers

[cdenk]

That looks like a fairly light construction structure, and probably
didn't weigh that much. The tire size/capacity (and they do overload
them for these short low speed hauls) then is used to determine the
number of tires required. Likely didn't weigh more than 20 tons (40,000
lbs.). Some of the weight was carried by the truck, say 10,000 lbs.
30,000 lbs can be carried legally on 12 tires, 3 axles of 4 tires. For a
short low speed haul, 2 axles with 8 tires, sure would be enough.
Interesting that the load got to the middle of the bridge before
collapsing, saying that they almost had enough capacity to get across.
:) Almost doesn't count except horseshoes. :)

John La Rooy wrote:
> On Fri, Jul 3, 2009 at 6:17 PM, Alan B. Pearce<Alan.B.Pearce@...> wrote:
>
>  
>> I am surprised it has only a set of wheels half way down the length. I would
>> have thought it would have needed more wheels than that.
>>
>>    
> You were right - it did :)
>  
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[cdenk]

Houses weight can vary, a stone or brick house can easily go over 100
tons (2000 lbs/ton). Much more massive structures are moved regularly,
including 100 year old 100' high brick light houses (Google Cape Hatteras)

All bridges have a design allowable load, and then that is reduced with
time, based on inspection. I have done bridge inspections on old
railroad bridges. The process is to check for loose rivets and bolts,
bent members, and measure thicknesses (whats not rust). This info is
taken back to the office, and using the info to calculate new allowable
loads. After the Silver Bridge Collapse across the Ohio River, the
Federal government (USA) mandated regular bridge inspections. Then the
bridges rated and should be posted loads are determined. If the bridge
load is not posted, generally it is assumed any load legal on highways
is allowed. Any load greater (including oversize) than legal loads
requires a permit. As part of the permit process, all bridges to be
crossed, dimension restrictions are checked, and the permit defines the
route allowed and sometimes the time of the day to be traveled.

Within the last week, our County Engineer closed a bridge near us. It is
a privately owned bridge on a public road (strange deal). The owner
doesn't want to fix it, and the county doesn't want a collapse. The
bridge has been posted with reduced loads for some time.

But, things happen, design errors, cheating on materials during
construction, not identifying a defect during inspection, etc. And then
there is the driver bootlegging (cheating) on the legal loads. The Ohio
state trooper stopped a truck that was severely overloaded with a large
stamping press in Central Ohio. The press started in Central Indiana,
and headed to central Pennsylvania. The load was so heavy, that it was
not permitted to travel the highways any further. Fortunately there was
a railroad track, near, and the load traveled by rail the rest of the
way. Many times these bootleg loads travel the back roads, where the
likelihood of overloading a bridge is more.

Most of the time, structural failures are details like connections or
minor members, and almost rarely its a main member (beam or column) that
fails. The I-35 bridge last year, Minneapolis, failure was due to some
under sized connection plates, corrosion, a contractor overloading with
repair construction materials, and finally rush hour traffic loads
brought it down.  Not unusual, a series of events, probably any one or
2, and no problem.

To answer #2, a single car, or even pedestrian traffic may be the limit,
or could be in the 100's of tons range. The full range. I drove a Ford
Bronco SUV with the family, weight right a 3 tons across the Royal Gorge
Bridge (highest suspension bridge in the USA - google for it),with a 3
ton limit. There was considerable pedestrian traffic. As we approached,
the foot traffic scattered quickly. We were really rocking the bridge!! :)


Rolf wrote:

> AGSCalabrese wrote:
>  
>> 3 Questions for an Engineer
>>
>> Question # 1:
>>   How much does a house weigh?
>>
>> Question # 2:
>> How much weight can a rural two-lane bridge Hold?
>>
>>
>>
>> See
>> http://oh-god.com:5080/dir/3Q/
>>
>>
>>
>> Question # 3
>>
>> IS THIS BE COVERED BY
>> HOUSE INSURANCE,
>> CAR INSURANCE,
>> OR,
>> DOES IT COME UNDER ROADSIDE ASSISTANCE ?
>>
>>  
>>    
>
>
> http://www.snopes.com/photos/accident/housebridge.asp
>
> OK.
>
> Rolf
>  

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[Nathan House-5]

Yes, it's real. That house looks to me what we in the U.S. know as prefab
homes.

http://en.wikipedia.org/wiki/Prefabricated_home

A lot of people with severe allergies (no, I'm not kidding) buy these things
because they are built inside factories, meaning when being built they don't
get rained or snowed on or what have you, and molds and the like don't
develop in them. I've been in one that was very large.. Two stories, garage,
very nice..
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[CDB-3]

:: o answer #2, a single car, or even pedestrian traffic may be the
:: limit,
:: or could be in the 100's of tons range. The full range. I drove a
:: Ford
:: Bronco SUV with the family, weight right a 3 tons across the Royal
:: Gorge
:: Bridge (highest suspension bridge in the USA - google for it),with
:: a 3
:: ton limit. There was considerable pedestrian traffic. As we
:: approached,
:: the foot traffic scattered quickly. We were really rocking the
:: bridge!! :)

In London (UK) there is Battersea Bridge, which is basically made of
wood - whilst cars streem over it into and out of London (used to be
time of day directional) the horseguards (their barracks used to be
just down the road in Chelsea), would have to dismount to cross the
bridge. The vibrations caused by a 20 odd horses trotting over the
bridge managed to be at the right natural oscillation frequency and
the bridge was in danger of falling down, but a a 10 ton truck roaring
over no problem.

Colin
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[cdenk]

Just like electrical circuits oscillate, structures do also. Wind and
earthquakes can cause big time vibrations, but floors can bounce up and
down from a person walking. Today the phenomenon is better understood
and certain floor weights/spans are avoided. For tall buildings the
latest is mass tuned dampers. Heavy weights near the top, suspended like
a pendulum or on low friction bearings with hydraulic dampers, just like
on your car, except much larger.

>
> In London (UK) there is Battersea Bridge, which is basically made of
> wood - whilst cars streem over it into and out of London (used to be
> time of day directional) the horseguards (their barracks used to be
> just down the road in Chelsea), would have to dismount to cross the
> bridge. The vibrations caused by a 20 odd horses trotting over the
> bridge managed to be at the right natural oscillation frequency and
> the bridge was in danger of falling down, but a a 10 ton truck roaring
> over no problem.
>
>
>  

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[CDB-3]

:: floors can bounce up and down from a person walking.

During the times of the Samurai, the Japanese
 used to have a Nightingale floor, special floor made of wood,
designed to creak and 'sing' if someone walked on it.

The target customer being a paraniod Samurai who feared being killed
in his sleep - the floor would wake him or his guards if such a thing
were attempted.

I wonder if the knowledge exists to build one today?

Colin
cdb, colin@... on 4/07/2009
 
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[Bob Blick-4]

cdb wrote:

>
> :: floors can bounce up and down from a person walking.
>
> During the times of the Samurai, the Japanese
>  used to have a Nightingale floor, special floor made of wood,
> designed to creak and 'sing' if someone walked on it.
>
> The target customer being a paraniod Samurai who feared being killed
> in his sleep - the floor would wake him or his guards if such a thing
> were attempted.
>
> I wonder if the knowledge exists to build one today?

Easy. Mount a strain gauge to any floor, connect it to a PIC, with a
piezo speaker for the sound of your choice :)

Cheers,

Bob
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[Nathan House-5]

>Easy. Mount a strain gauge to any floor, connect it to a PIC, with a
>piezo speaker for the sound of your choice :)

Or just live in a really old house, they have these built in floor alarms
for free :-) Trust me, I used to live in one. I never really thought of it
as a safety feature though...
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[John Gardner-3]

20-odd hoss & riders that different from 10-ton truck?

Jack
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[cdenk]

Oh, yes, it's the resonance frequency and the frequency of whatever,
like horses or other things in unison.  Think of a child on a playground
swing. At the right time a small push and the amplitude is greater if
that push is right after the extreme limit of travel. If the push is
just before the limit, amplitude is reduced.

John Gardner wrote:
> 20-odd hoss & riders that different from 10-ton truck?
>
> Jack
>  
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[Russell McMahon-4]

If nobody has mentioned the Tacoma Narrows bridge yet  ... .
A fine early experience of resonance and the problems with cable stayed
bridges.
Best of all, despite the fantastic film footage, nobody was killed in the
breaking of this bridge. Several people would have thought they were
candidates.

This is by far the best film footage of the event that i have ever seen -
well worth watching.
Sound track is execrable. Can't have everything :-).
http://www.youtube.com/watch?v=j-zczJXSxnw
This may have been "post processed" and possibly colorised.
This is more like what is usually seen.
Has better footage of the actual moment of collapse.
http://www.youtube.com/watch?v=HxTZ446tbzE&feature=related
Script identical in most cases.
Prof xxx is brave beyond belief (but, see below).
Two men seen at end of footage MUST be engineers ;-).

This version provides other color footage.
it also says the dog rescue story is untrue and that the dog died.
http://www.youtube.com/watch?v=vu4LPTsy_xY&feature=related

_________________________

The london Millenium pedestrian only bridge suffered from a subtler fatal
flaw which was discovered soon after it opened. It was closed again soon
after and took AFAIR about 2 years to sort out.
The second stage of the problem is resonance if people walk in step - the
designers were well aware of this and didn't see it as a problem. BUT,
The first stage of the problem was an effect discovered many decades earlier
and then largely forgotten - if a bridge with a natural oscillatory
frequency is excited by random input (lots of pedestrians) it can produce a
forcing signal that is not large enough to be damaging to the structure BUT
which drives the exciters towards the resonance point. ie the walkers resond
to the bridghe's movements by altering thei stride and gait somewhat and are
driven into resonance with the bridge so that THEN they drive the resonance
more solidly. The MB had substantial dampers fitted which preventthis - they
are visible in photos if you know that there is something tgere to look for.

_______________

Anti-resoant dampers for use in de-swaying tall buildings were mentioned.
Taipei 101was at one time the tallest building in the world by AFAIR 5 of
the 6 metrics used to measure building height as agreed to by the tall
building builders association (names have been mutilated due to imperfect
memory, facts approx correct). One floor below the viewing deck there is a
large and very heavy and very high tech suspended weight - approximately
stepped spherical.
Ah well ... Gargoyle says ...

http://en.wikipedia.org/wiki/Taipei_101
http://www.popularmechanics.com/technology/industry/1612252.html


World's tallest at May 2005 (I was there ???)
Burj Dubai is now taller BUT will not officially meet the definition of a
"building" until later this year (fwiw).


1667 ft. 660 ft. from a major fault line in Taiwan, ... could be subjected
to earthquakes, typhoons and fierce winds ... 730-ton tuned mass damper
(TMD). It acts like a giant pendulum to counteract the building's
movement--reducing sway due to wind by 30 to 40 percent. Constructed by
specialty engineering firm Motioneering, the damper was too heavy to be
lifted by crane and had to be assembled on-site. Eight steel cables form a
sling to support the ball, while eight viscous dampers act like shock
absorbers when the sphere shifts. Able to move 5 ft. in any direction, the
Taipei TMD is the world's largest and heaviest. This gold-colored orb is on
view from restaurants, bars and observation decks between the 88th and 92nd
stories. A bumper ring prevents the ball from swaying too far, should that
much swaying ever need to occur. Our recommendation, in that case, would be
an immediate egress to firmer ground.








2009/7/5 Carl Denk <cdenk@...>

> Oh, yes, it's the resonance frequency and the frequency of whatever,
> like horses or other things in unison.  Think of a child on a playground
> swing. At the right time a small push and the amplitude is greater if
> that push is right after the extreme limit of travel. If the push is
> just before the limit, amplitude is reduced.
>
> John Gardner wrote:
> > 20-odd hoss & riders that different from 10-ton truck?
> >
> > Jack
> >
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[Tamas Rudnai]

On Sat, Jul 4, 2009 at 3:29 AM, cdb <colin@...> wrote:

> During the times of the Samurai, the Japanese
>  used to have a Nightingale floor, special floor made of wood,
> designed to creak and 'sing' if someone walked on it.
>
> The target customer being a paraniod Samurai who feared being killed
> in his sleep - the floor would wake him or his guards if such a thing
> were attempted.
>
> I wonder if the knowledge exists to build one today?


Nowadays we are using PIR sensors and 120dB sirens to make noise when
someone is attempt to walk in our house while we are sleeping in upstairs
:-)

Tamas
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[AGSCalabrese]

See New Tacoma Bridge
http://www.nwrain.net/~newtsuit/recoveries/narrows/cb.htm
Gus

>
> On Jul 4, 2009, at 8:35 AM, Russell McMahon wrote:
>
> If nobody has mentioned the Tacoma Narrows bridge yet  ... .
> A fine early experience of resonance and the problems with cable  
> stayed
> bridges.
> Best of all, despite the fantastic film footage, nobody was killed  
> in the
> breaking of this bridge. Several people would have thought they were
> candidates.
>
> This is by far the best film footage of the event that i have ever  
> seen -
> well worth watching.
> Sound track is execrable. Can't have everything :-).
> http://www.youtube.com/watch?v=j-zczJXSxnw
> This may have been "post processed" and possibly colorised.
> This is more like what is usually seen.
> Has better footage of the actual moment of collapse.
> http://www.youtube.com/watch?v=HxTZ446tbzE&feature=related
> Script identical in most cases.
> Prof xxx is brave beyond belief (but, see below).
> Two men seen at end of footage MUST be engineers ;-).
>
> This version provides other color footage.
> it also says the dog rescue story is untrue and that the dog died.
> http://www.youtube.com/watch?v=vu4LPTsy_xY&feature=related
>
> _________________________
>
> The london Millenium pedestrian only bridge suffered from a subtler  
> fatal
> flaw which was discovered soon after it opened. It was closed again  
> soon
> after and took AFAIR about 2 years to sort out.
> The second stage of the problem is resonance if people walk in step  
> - the
> designers were well aware of this and didn't see it as a problem. BUT,
> The first stage of the problem was an effect discovered many decades  
> earlier
> and then largely forgotten - if a bridge with a natural oscillatory
> frequency is excited by random input (lots of pedestrians) it can  
> produce a
> forcing signal that is not large enough to be damaging to the  
> structure BUT
> which drives the exciters towards the resonance point. ie the  
> walkers resond
> to the bridghe's movements by altering thei stride and gait somewhat  
> and are
> driven into resonance with the bridge so that THEN they drive the  
> resonance
> more solidly. The MB had substantial dampers fitted which  
> preventthis - they
> are visible in photos if you know that there is something there to  
> look for.
>
> _______________
>
> Anti-resoant dampers for use in de-swaying tall buildings were  
> mentioned.
> Taipei 101was at one time the tallest building in the world by AFAIR  
> 5 of
> the 6 metrics used to measure building height as agreed to by the tall
> building builders association (names have been mutilated due to  
> imperfect
> memory, facts approx correct). One floor below the viewing deck  
> there is a
> large and very heavy and very high tech suspended weight -  
> approximately
> stepped spherical.
> Ah well ... Gargoyle says ...
>
> http://en.wikipedia.org/wiki/Taipei_101
> http://www.popularmechanics.com/technology/industry/1612252.html
>
>
> World's tallest at May 2005 (I was there ???)
> Burj Dubai is now taller BUT will not officially meet the definition  
> of a
> "building" until later this year (fwiw).
>
>
> 1667 ft. 660 ft. from a major fault line in Taiwan, ... could be  
> subjected
> to earthquakes, typhoons and fierce winds ... 730-ton tuned mass  
> damper
> (TMD). It acts like a giant pendulum to counteract the building's
> movement--reducing sway due to wind by 30 to 40 percent. Constructed  
> by
> specialty engineering firm Motioneering, the damper was too heavy to  
> be
> lifted by crane and had to be assembled on-site. Eight steel cables  
> form a
> sling to support the ball, while eight viscous dampers act like shock
> absorbers when the sphere shifts. Able to move 5 ft. in any  
> direction, the
> Taipei TMD is the world's largest and heaviest. This gold-colored  
> orb is on
> view from restaurants, bars and observation decks between the 88th  
> and 92nd
> stories. A bumper ring prevents the ball from swaying too far,  
> should that
> much swaying ever need to occur. Our recommendation, in that case,  
> would be
> an immediate egress to firmer ground.
>
>

2009/7/5 Carl Denk <cdenk@...>

> Oh, yes, it's the resonance frequency and the frequency of whatever,
> like horses or other things in unison.  Think of a child on a  
> playground
> swing. At the right time a small push and the amplitude is greater if
> that push is right after the extreme limit of travel. If the push is
> just before the limit, amplitude is reduced.
>
> John Gardner wrote:
>> 20-odd hoss & riders that different from 10-ton truck?
>>
>> Jack
>>
> --
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>

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[Alan B. Pearce-2]

>1667 ft. 660 ft. from a major fault line in Taiwan, ... could be
>subjected to earthquakes, typhoons and fierce winds ... 730-ton
>tuned mass damper (TMD). It acts like a giant pendulum to counteract
>the building's movement--reducing sway due to wind by 30 to 40
>percent. Constructed by specialty engineering firm Motioneering,
>the damper was too heavy to be lifted by crane and had to be
>assembled on-site. Eight steel cables form a sling to support the
>ball, while eight viscous dampers act like shock absorbers when the
>sphere shifts. Able to move 5 ft. in any direction, the Taipei TMD
>is the world's largest and heaviest. This gold-colored orb is on
>view from restaurants, bars and observation decks between the 88th
>and 92nd stories. A bumper ring prevents the ball from swaying too
>far, should that much swaying ever need to occur. Our recommendation,
>in that case, would be an immediate egress to firmer ground.

I have seen a TV program about this building, and it included some cell
phone footage of the ball moving as the building was buffeted during a
typhoon. Looked pretty awesome, but somehow I don't think I want to be
around in a typhoon anyway ...

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