Structural Engineering: 2007-05-20

Saturday, May 26, 2007

Re: 9-11 Wackos

Check this out...simply brilliant.

http://www.youtube.com/watch?v=gxRvExqN7_E

-g (working over the holiday weekend :-< )

On 5/26/07, Scott Maxwell <smaxwell@engin.umich.edu> wrote:

The demonstration in the bathtub in the video was hilarious!

Scott
Adrian, MI

On Fri, 25 May 2007, Josh Comfort wrote:

> I am fascinated with the conspiracy theorists, but purely in a "have to
> stare at a car accident" sort of way.  Every day I look forward to the crap
> Rosie O'donnell spews from her fat face.  I especially liked the day she
> spouted off about how 9-11 was the first instance in the history of the
> world where fire melted steel.  Yeah, things like W16x31s and bar joists are
> natural steel formations just waiting to be happened upon and plucked out of
> the earth.
>
> Anyhow, for those anti-conspiracy theorists out there you may find this
> website amusing: http://www.thebestpageintheuniverse.net/c.cgi?u=af07.  My
> favorite part is the embedded video about half-way down the main page.
>
> Josh Comfort, P.E.
> Spokane, WA
>   -----Original Message-----
>   From: Gerard Madden, SE [mailto:gmse4603@gmail.com]
>   Sent: Friday, May 25, 2007 8:55 AM
>   To: seaint@seaint.org
>   Subject: 9-11 Wackos
>
>
>   As I've probably mentioned before, I'm in a band. One of the greatest joys
> of that endeavor is having to be involved in the land of MYSPACE to promote
> my band *sarcasm intended*
>
>   Anyway from time to time, your "friends" on this thing send you these
> messages called bulletins (like mass emails). I got one yesterday that
> directed me to a 90 minute film on youtube about the 9-11 conspiracy stuff.
>
>   Let me preface this by saying I think GWB is a national disgrace, as is
> the war in Iraq, but never for one second have ever had any incling that
> there was some inside job or conspiracy by the US Gov.
>
>   So I watched this whole video. It changed nothing in my thought process of
> what happened. However, It's presented in such a way that I think it's
> dangerous and irresponsible. I could easily see non-technical types and
> young people believing this stuff because of it's presentation and the
> general dismay young people have with current situations (and old too
> sometimes). I was able to find more stuff on youtube afterward where some
> guys from Popular Mechanics debated the two guys who made the film. Half of
> you probably already know this.
>
>   If you haven't seen it, I suggest you watch purely for the purpose of
> witnessing how things can be pulled out of thin air by these conspiracy
> theorist as they try to insuate but never proove anything. Email me
> privately if you need to know the name of the thing, but it's not that tough
> to find on youtube.
>
>   I also found it extremely curious that the so-called experts they had
> quoted on their film explaining what "actually happened" none of them were
> structural engineers and the misuse of the term "melting of steel"
> repeatedly.
>
>
>   --
>   -gm
>

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--
-gm

RE: 9-11 Wackos

The demonstration in the bathtub in the video was hilarious!

Scott
Adrian, MI

On Fri, 25 May 2007, Josh Comfort wrote:

> I am fascinated with the conspiracy theorists, but purely in a "have to
> stare at a car accident" sort of way. Every day I look forward to the crap
> Rosie O'donnell spews from her fat face. I especially liked the day she
> spouted off about how 9-11 was the first instance in the history of the
> world where fire melted steel. Yeah, things like W16x31s and bar joists are
> natural steel formations just waiting to be happened upon and plucked out of
> the earth.
>
> Anyhow, for those anti-conspiracy theorists out there you may find this
> website amusing: http://www.thebestpageintheuniverse.net/c.cgi?u=af07.

My
> favorite part is the embedded video about half-way down the main page.
>
> Josh Comfort, P.E.
> Spokane, WA
> -----Original Message-----
> From: Gerard Madden, SE [mailto:gmse4603@gmail.com]
> Sent: Friday, May 25, 2007 8:55 AM
> To: seaint@seaint.org
> Subject: 9-11 Wackos
>
>
> As I've probably mentioned before, I'm in a band. One of the greatest joys
> of that endeavor is having to be involved in the land of MYSPACE to promote
> my band *sarcasm intended*
>
> Anyway from time to time, your "friends" on this thing send you these
> messages called bulletins (like mass emails). I got one yesterday that
> directed me to a 90 minute film on youtube about the 9-11 conspiracy stuff.
>
> Let me preface this by saying I think GWB is a national disgrace, as is
> the war in Iraq, but never for one second have ever had any incling that
> there was some inside job or conspiracy by the US Gov.
>
> So I watched this whole video. It changed nothing in my thought process of
> what happened. However, It's presented in such a way that I think it's
> dangerous and irresponsible. I could easily see non-technical types and
> young people believing this stuff because of it's presentation and the
> general dismay young people have with current situations (and old too
> sometimes). I was able to find more stuff on youtube afterward where some
> guys from Popular Mechanics debated the two guys who made the film. Half of
> you probably already know this.
>
> If you haven't seen it, I suggest you watch purely for the purpose of
> witnessing how things can be pulled out of thin air by these conspiracy
> theorist as they try to insuate but never proove anything. Email me
> privately if you need to know the name of the thing, but it's not that tough
> to find on youtube.
>
> I also found it extremely curious that the so-called experts they had
> quoted on their film explaining what "actually happened" none of them were
> structural engineers and the misuse of the term "melting of steel"
> repeatedly.
>
>
> --
> -gm
>

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*
* This email was sent to you via Structural Engineers
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Friday, May 25, 2007

Re: 9-11 Wackos

Will, thanks for the link. I skimmed it briefly and will read it more thoroughly, but it seems very well done and supports what I and other have been saying, although in a much more elegant and well presented manner.

-g

On 5/25/07, Will Haynes <gtg740p@gmail.com> wrote:

I apologize if this has already been discussed on the list and I missed it, but I attended a seminar by Dr. Bazant which was extremely impressive. I haven't paid any attention to all the other theories around the Internet, but he also debunked them in the seminar. I recommend any lecture by this extremely intelligent guy. He addressed all the mechanics in the seminar.

http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/405.pdf

Will Haynes, PE

On 5/25/07, Gerard Madden, SE < gmse4603@gmail.com> wrote:
The columns were designed to hold the total load with regular/uniform unbraced lengths ( i.e. the floor to floor heights). Load was redistrubuted due to the impact of the plane. Unbraced lengths of columns changed due to failure of the trusses falling down from the fire and also the weakening of the steel due to heat (notice I didn't say MELTING). Then the first collapse or buckling takes place and stuff starts to move down when Mass (increasing @ each floor) x Acceleration (constant) takes over. Momemtum ( increasing mass x increasing velocity) @ each floor overcomes the static load capacity of the floors while the impact is a continuously concussive force on the overloaded columns that have to top stability as the building comes down. Like crushing a can of soda over and over only the crushing force increases each time. WTC-7, 100 yards away was hit with debris, so there was no clean true pancaking.

If the building tipped over like a tree being cut, it's obviously more clear cut. But the structure was damage up high, not at it's base.

According to the little bit I've watch from the popular mechanics guys, the WTC 7 building had about 25% of its lower support obliterated from debris of the falling towers. They also say in layman's terms, that it had very little axial redundancy at its base due to being built over an adjacent structure, so it had only a few main columns at it's base

That's how I see it and it makes sense to me.
-g

On 5/25/07, ECVAl3@aol.com < ECVAl3@aol.com> wrote:

Lets say the floors give way instantaneously due to the increase in mass plus increase in acceleration and it all falls to the ground as if in free fall. Weren't the interior and exterior columns designed to support the total weight (live + dead load) of the structure above each level and if the floor structure instantaneously separated from the columns wouldn't the majority of the columns still be standing, even momentarily, after the floors collapsed? Wouldn't the steel columns on the exterior of the building flex and twist, possibly snapping and fly considerable distance from the building or fall away from the building mostly intact?

The videos don't show this type of behavior. Why not?

S.Macie, CA.P.E., HI.S.E.

See what's free at AOL.com.

--
-gm

--
-gm

Re: 9-11 Wackos

On May 25, 2007, at 2:24 PM, Mark E. Deardorff wrote:

> "increasing mass and acceleration" To be technically accurate,
> acceleration does not change. It is constant except that it is
> immeasurably higher at the foundation than at the penthouse due to
> its closer proximity to the center of mass of the Earth.
To be really technically accurate the force of gravity doesn't
change, but the acceleration does. Prior to impact a floor does not
move with the gravity force equilibrated by the support reactions.
Since there is no net force, the acceleration is zero. when the
falling wreckage strikes the flor the connections break and the
combined mass is no longer in equilibrium and accelerates at 32.2 ft/
sec^2. Prior to impact the falling wreckage accelerates at 32.2 ft/
sec^2 except momentarily at impact when an upward force (that
required to break all the support connections) exists countering that
of gravity, so the impacting wreckage decelerates briefly, since the
net force on the wreckage is the gravity force less the connection
resistance.

Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw@skypoint.com | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania
1864)
http://www.skypoint.com/~chrisw/

******* ****** ****** ****** ******* ****** ****** ********

Re: Curved Prestressed Concrete Box Girders

Arvind,

Try articles published by Dilger, W.H.

Regards,

H. Daryl Richardson

----- Original Message -----
From: "Arvind Salecha" <arvindsalecha@yahoo.com>
To: <seaint@seaint.org>
Sent: Friday, May 25, 2007 9:07 AM
Subject: Curved Prestressed Concrete Box Girders

> Fellow Engineers,
> I am designing a Curved Prestressed Concrete Box
> Girder Bridge with 50m radius of curvature and 35 m
> span.
>
> Can you guys suggest a good reference book/ article
> for this.
>
> Thanx,
> Arvind Salecha
>
> Arvind Salecha
> Structural Consultant
>
> Infrastructure Technology & Consultancy Services.
> 200/1, Ist floor, 3rd Main, Chamrajpet,
> Bangalore - 560018
> Karnataka, India
> Mobile - +91-9342129391
> Land line (0821) 2431059 (Mysore)
>
>
> ******* ****** ******* ******** ******* ******* ******* ***
> * Read list FAQ at: http://www.seaint.org/list_FAQ.asp
> *
> * This email was sent to you via Structural Engineers
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> *

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> *
> * Questions to seaint-ad@seaint.org. Remember, any email you
> * send to the list is public domain and may be re-posted
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Re: 9-11 Wackos

I apologize if this has already been discussed on the list and I missed it, but I attended a seminar by Dr. Bazant which was extremely impressive. I haven't paid any attention to all the other theories around the Internet, but he also debunked them in the seminar. I recommend any lecture by this extremely intelligent guy. He addressed all the mechanics in the seminar.

http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/405.pdf

Will Haynes, PE

On 5/25/07, Gerard Madden, SE <gmse4603@gmail.com> wrote:

The columns were designed to hold the total load with regular/uniform unbraced lengths (i.e. the floor to floor heights). Load was redistrubuted due to the impact of the plane. Unbraced lengths of columns changed due to failure of the trusses falling down from the fire and also the weakening of the steel due to heat (notice I didn't say MELTING). Then the first collapse or buckling takes place and stuff starts to move down when Mass (increasing @ each floor) x Acceleration (constant) takes over. Momemtum ( increasing mass x increasing velocity) @ each floor overcomes the static load capacity of the floors while the impact is a continuously concussive force on the overloaded columns that have to top stability as the building comes down. Like crushing a can of soda over and over only the crushing force increases each time. WTC-7, 100 yards away was hit with debris, so there was no clean true pancaking.

If the building tipped over like a tree being cut, it's obviously more clear cut. But the structure was damage up high, not at it's base.

According to the little bit I've watch from the popular mechanics guys, the WTC 7 building had about 25% of its lower support obliterated from debris of the falling towers. They also say in layman's terms, that it had very little axial redundancy at its base due to being built over an adjacent structure, so it had only a few main columns at it's base

That's how I see it and it makes sense to me.
-g

On 5/25/07, ECVAl3@aol.com < ECVAl3@aol.com> wrote:

Lets say the floors give way instantaneously due to the increase in mass plus increase in acceleration and it all falls to the ground as if in free fall. Weren't the interior and exterior columns designed to support the total weight (live + dead load) of the structure above each level and if the floor structure instantaneously separated from the columns wouldn't the majority of the columns still be standing, even momentarily, after the floors collapsed? Wouldn't the steel columns on the exterior of the building flex and twist, possibly snapping and fly considerable distance from the building or fall away from the building mostly intact?

The videos don't show this type of behavior. Why not?

S.Macie, CA.P.E., HI.S.E.

See what's free at AOL.com.

--
-gm

Re: 9-11 Wackos

The columns were designed to hold the total load with regular/uniform unbraced lengths (i.e. the floor to floor heights). Load was redistrubuted due to the impact of the plane. Unbraced lengths of columns changed due to failure of the trusses falling down from the fire and also the weakening of the steel due to heat (notice I didn't say MELTING). Then the first collapse or buckling takes place and stuff starts to move down when Mass (increasing @ each floor) x Acceleration (constant) takes over. Momemtum ( increasing mass x increasing velocity) @ each floor overcomes the static load capacity of the floors while the impact is a continuously concussive force on the overloaded columns that have to top stability as the building comes down. Like crushing a can of soda over and over only the crushing force increases each time. WTC-7, 100 yards away was hit with debris, so there was no clean true pancaking.

If the building tipped over like a tree being cut, it's obviously more clear cut. But the structure was damage up high, not at it's base.

According to the little bit I've watch from the popular mechanics guys, the WTC 7 building had about 25% of its lower support obliterated from debris of the falling towers. They also say in layman's terms, that it had very little axial redundancy at its base due to being built over an adjacent structure, so it had only a few main columns at it's base

That's how I see it and it makes sense to me.
-g

On 5/25/07, ECVAl3@aol.com < ECVAl3@aol.com> wrote:

Lets say the floors give way instantaneously due to the increase in mass plus increase in acceleration and it all falls to the ground as if in free fall. Weren't the interior and exterior columns designed to support the total weight (live + dead load) of the structure above each level and if the floor structure instantaneously separated from the columns wouldn't the majority of the columns still be standing, even momentarily, after the floors collapsed? Wouldn't the steel columns on the exterior of the building flex and twist, possibly snapping and fly considerable distance from the building or fall away from the building mostly intact?

The videos don't show this type of behavior. Why not?

S.Macie, CA.P.E., HI.S.E.

See what's free at AOL.com.

--
-gm

Re: OT: HP-750C

Alden-

Not as good as a photo but hope this helps

http://www.superglobalmeganet.com/filz/DesignJet_700_750C_750C_Plus_and_755CM.pdf

cheers
Bob

On 5/25/07, Alden Manipula <amanipula@novagroupinc.net> wrote:

Hi all,

Way off topic here.

I'm doing some maintenance on a HP-750C, replacing the belt drive. However, i'm having problems w/ the trailing cable (the ribbon cable that is connected to the cartridge carriage). I can't get the orientation correct so the carriage travels without binding it up. I should have taken a picture!

So, can anyone who has one of these printers possibly take a picture of how it's oriented from the carriage. I'm sure it runs underneath, but i'm confused as to how to twist it correctly to run smoothly.

TIA

Alden

Re: 9-11 Wackos

Lets say the floors give way instantaneously due to the increase in mass plus increase in acceleration and it all falls to the ground as if in free fall. Weren't the interior and exterior columns designed to support the total weight (live + dead load) of the structure above each level and if the floor structure instantaneously separated from the columns wouldn't the majority of the columns still be standing, even momentarily, after the floors collapsed? Wouldn't the steel columns on the exterior of the building flex and twist, possibly snapping and fly considerable distance from the building or fall away from the building mostly intact?

The videos don't show this type of behavior. Why not?

S.Macie, CA.P.E., HI.S.E.

See what's free at AOL.com.

Re: 9-11 Wackos

I did write" increasing mass and acceleration" and that's what I meant, not increasing mass and increasing acceleration, because as you said, the rate of acceleration is not changing. Next time I will write PLUS in between to be more clear. But Acceleration can change, just not in gravity freefall assuming no wind resistance and terminal speed is not achieved.

-g

On 5/25/07, Mark E. Deardorff <mdeardorff@burkett-wong.com> wrote:

"increasing mass and acceleration" To be technically accurate, acceleration does not change. It is constant except that it is immeasurably higher at the foundation than at the penthouse due to its closer proximity to the center of mass of the Earth.

Mark E. Deardorff, S.E.

Structural Engineer

3434 4th Ave

San Diego, CA 92103

P 619.299.5550

F 619.299.9934

mdeardorff@burkett-wong.com

From: Gerard Madden, SE [mailto:gmse4603@gmail.com]
Sent: Friday, May 25, 2007 12:13 PM
To: seaint@seaint.org
Subject: Re: 9-11 Wackos

Exactly.

And remember, the resistance strength at each floor is constant. So as you go down the building, each floor has the same capacity to resist the pancacking, but the force cannot be overcome due to the ever increasing mass and acceleration to the point that it becomes neglible to momentarily slow down the fall.

-g

On 5/25/07, Christopher Wright <chrisw@skypoint.com> wrote:

> Maybe I just don't get it but, in my mind, when an object in motion
> meets a stationary object, there is a lose of momentum thereby
> slowing down the acceleration process.
Momentum is conserved in a collision, although energy may be
dissipated. If you think of each floor as a rigid body, the force of
impact acts to speed up the lower floor and slow down in upper floor,
such the mu1Vu1 = ml1Vl2+mu2Vu2. The upper floor will have to slow
down a little bit momentarily becasue it is subject to the reaction
of the force needed to break the support connections for the lower
floor.

Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw@skypoint.com   | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania
1864)
http://www.skypoint.com/~chrisw/

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
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*   Questions to seaint-ad@seaint.org . Remember, any email you
*   send to the list is public domain and may be re-posted
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--
-gm

--
-gm

RE: Sheffield Joists

The bar joist section of Sheffield was sold to Armco. I believe this
happened in the early 197'0s. I know Armco owned them in the mid 1970's.
Armco changed the chords to cold formed hat sections to make the J series
which did not last long until they went to 50 grade steel and went to the H
series.

Regards,
Harold Sprague

>From: Michael Hemstad <mhemstad@mbjeng.com>
>Reply-To: <seaint@seaint.org>
>To: seaint@seaint.org
>Subject: Sheffield Joists
>Date: Thu, 24 May 2007 11:52:50 -0500
>
>I have a joist tag from a 14 inch open-web bar joist that reads "1678
>146-195F" and which was made by the Sheffield Steel Corporation. The joist
>chords are hot-rolled angles.
>
>I don't know when the structure (a mezzanine floor) was built; a reasonable
>guess would be the 1970's or 1980's, but it is an addition to a much older
>building and we have no drawings.
>
>I've looked through the SJI 50 Year Digest, but without knowing when it was
>built, I don't get very far.
>
>Does anyone know how to determine what type of joist (S, H, J, etc.) this
>tag comes from? I have some old Sheffield tables, but again without more
>information I come up short.
>
>Thanks for any help.
>
>Mike Hemstad
>MBJ
>Minneapolis, Minnesota
>
>Michael Hemstad, P.E.
>
>
>Meyer, Borgman and Johnson, Inc.
>
>12 South Sixth Street
>Suite 810
>Minneapolis, MN 55402
>(612) 338-0713 (main)
>(612) 604-3621 (direct)
>(612) 337-5325 (fax)
>www.mbjeng.com
>
><< LogoForE-mailSignature.bmp >>

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Re: High lift grouting

ACI 530 calls for cleanouts @ 32" max. o.c. with a 3" min. dimension for grout pours over 5'-0" in the execution part of the document.

----- Original Message -----
From: "Doug Mayer"
To: seaint@seaint.org
Subject: High lift grouting
Date: Fri, 25 May 2007 10:25:20 -0700

List,

I have a CMU wall building in Washington (state) being built that has fully grouted walls and reinforcing at 8" o.c. each way. The contractor wants to do high lift grouting in lieu of the low-lifts, which is fine with me. However, the topic of cleanouts has become an issue and I'm not sure of the correct answer.

They would like to do cleanouts at 32" o.c., but I know that older codes and the Concrete Masonry Association of California and Nevada specify that cleanouts are to occur at each vertical cell with reinforcing, or continuous special inspection is to be provided. But, looking at the IBC 2003 and ACI 530-02 – the codes for this project – I can't seem to find any reference or specification for cleanout requirements. Any ideas?

Thanks for the help,

Doug Mayer, SE

Structural Engineer

TaylorTeter

Partnership

Bart Needham, SE Principal, nbse associates, inc. Office 206-780-6822 Office 805-452-8152 Fax    206-780-6683 Fax    208-693-3667 Mobile 206-300-2346  Office locations: 629 State Street #230 Santa Barbara, CA  93101  205 Fairview Lane Suite 100 Paso Robles, CA  93446  365 Ericksen Ave. NE Suite 328 Bainbridge Island, WA  98110  Mail and Deliveries: 321 High School Rd. NE Suite D-3 PMB 216 Bainbridge Island, WA  98110

Re: High lift grouting

Doug,

Section 3.2F of the Specification of the MSJC (i.e. ACI 530.1-02).

It states:

"Cleanouts - Provide cleanouts in the bottom of course of masonry for each
grout pour, when the grout pour height exceeds 5 ft.

1. Construct cleanouts so that the space to be grouted can be cleaned and
inspected. In solid grouted masonry, space cleanouts horizontally a
maximum of 32 in. on center.

2. Construct cleanouts with an opening of sufficient size to permit
removal of debris. The minimum opening dimension shall be 3 in.

3. After cleaning, close cleanouts with closures braced to resist grout
pressure."

HTH,

Scott
Adrian, MI

On Fri, 25 May 2007, Doug Mayer wrote:

> List,
>
>
>
> I have a CMU wall building in Washington (state) being built that has
> fully grouted walls and reinforcing at 8" o.c. each way. The contractor
> wants to do high lift grouting in lieu of the low-lifts, which is fine
> with me. However, the topic of cleanouts has become an issue and I'm
> not sure of the correct answer.
>
>
>
> They would like to do cleanouts at 32" o.c., but I know that older codes
> and the Concrete Masonry Association of California and Nevada specify
> that cleanouts are to occur at each vertical cell with reinforcing, or
> continuous special inspection is to be provided. But, looking at the
> IBC 2003 and ACI 530-02 - the codes for this project - I can't seem to
> find any reference or specification for cleanout requirements. Any
> ideas?
>
>
>
> Thanks for the help,
>
>
>
> Doug Mayer, SE
>
> Structural Engineer
>
>
>
> TaylorTeter
>
> Partnership
>
>
>
>
>
>
>
>

******* ****** ****** ****** ******* ****** ****** ********

Re: High lift grouting

Doug-
Don't know if you're in UBC country but the definition of "Cleanout" in Section 2101 reads:
"CLEANOUT is an opening to the bottom of a grout space of sufficient size and spacing to allow removal of debris." The definition in the 2006 IBC is almost identical.

If there is no communication with adjacent cells without cleanouts, how can the debris removed?

Further, UBC Section 2104.6.1, par. 7 states: "Cleanouts shall be provided for all grout pours over 5 feet (1524 mm) in height." The 2006 IBC refers to ACI 530 and 530.1 which I believe require cleanouts at every vertical reinforcing bar location and at a minimum horizontal spacing of 32 inches when the grout pour height exceeds 5 feet.
Regards,
Bill Cain, SE
Berkeley CA

-----Original Message-----
From: Doug Mayer
To: seaint@seaint.org
Sent: Fri, 25 May 2007 10:54 am
Subject: RE: High lift grouting

Mark,

I agree, but my point is that I can't find a statement supporting this in the code(s).

Thanks,

Doug Mayer, SE

Structural Engineer

TaylorTeter

Partnership

From: Mark E. Deardorff [mailto:mdeardorff@burkett-wong.com]
Sent: Friday, May 25, 2007 10:40 AM
To: seaint@seaint.org
Subject: RE: High lift grouting

How do they propose to remove debris from the three out of four cells that aren't open for inspection? Maybe I am wrong but I thought that is what "cleanouts" were for.

Mark E. Deardorff, S.E.

Structural Engineer

3434 4th Ave

San Diego, CA 92103

P 619.299.5550

F 619.299.9934

mdeardorff@burkett-wong.com

From: Doug Mayer [mailto:doug.mayer@taylorteter.com]
Sent: Friday, May 25, 2007 10:25 AM
To: seaint@seaint.org
Subject: High lift grouting

List,

I have a CMU wall building in Washington (state) being built that has fully grouted walls and reinforcing at 8" o.c. each way. The contractor wants to do high lift grouting in lieu of the low-lifts, which is fine with me. However, the topic of cleanouts has become an issue and I'm not sure of the correct answer.

They would like to do cleanouts at 32" o.c., but I know that older codes and the Concrete Masonry Association of California and Nevada specify that cleanouts are to occur at each vertical cell with reinforcing, or continuous special inspection is to be provided. But, looking at the IBC 2003 and ACI 530-02 – the codes for this project – I can't seem to find any reference or specification for cleanout requirements. Any ideas?

Thanks for the help,

Doug Mayer, SE

Structural Engineer

TaylorTeter

Partnership

AOL now offers free email to everyone. Find out more about what's free from AOL at AOL.com.

RE: 9-11 Wackos

Once the first floor(s) collapsed they entered freefall. These floors then collided with the floor below. The colums then would resist the falling mass. The amount of resistance they can offer depends on the ratio of design stress to buckling stress and the maximum buckling length. If the column cannot do enough work on the falling mass it will fail and another floor will be added to the mass. Now this mass will be in free fall until it collides with the next floor. This will be repeated until either the columns can slow down the mass and stop the collapse or until all floors are collapsed.

So basically a number of floors fail and the mass falls at free fall until it hits the floor below; then the columns resist until failure over some buckling length (they can only buckle so far until either the column fails or the beam to column connections fail). The mass then is in free fall for the remainder of the floor to floor height.

It is easy to setup a spreadsheet to model this behaivor. Assumptions need to be made about how many floors initially failed, the column saftey factor, maximum buckling length of the column, and the floor to floor height. Then calculate the velocity and time at the initial impact assuming initial velocity of zero and freefall for the full floor to floor height. Calculate the work done by the columns on the mass(Saftey factor X buckling length X mass X gravity) if this is greater than the kinetic energy of the mass before impact no failure occurs. Otherwise, subtract the column resistance from the kinetic energy before the impact and calculate a new velocity based on the new mass. Use the average of new velocity and impact velocity and the buckling length to average the impact time. Now calculate the impact velocity at the next floor and time to reach the floor based on the free fall distance of the floor to floor height minus the buckling length of the previously failed columns and the velocity after the last impact. Just repeat this for all floors.

If you assume faluire took place on the 94 floor, all floors above initially failed, floor to floor height of 12'-3", a column safety factor of 2, and a maximum buckling length of 1 foot, I calculate that the total time of collapse is approximately 12 seconds.

buckling length 2 feet - 13.4s

3 feet - 17.5s

4 feet - 41 s

5 feet - collapse stops at 92 floor

From: ECVAl3@aol.com [mailto:ECVAl3@aol.com]
Sent: Friday, May 25, 2007 1:52 PM
To: seaint@seaint.org
Subject: Re: 9-11 Wackos

In a message dated 5/25/2007 10:33:37 A.M. Pacific Daylight Time, gmse4603@gmail.com writes:

Freefall: mass and acceleration....an ever increasing mass (each floor falling on another) and acceleration (those things were too heavy to reach terminal speed from wind resistance) ...makes perfect sense to me.

Maybe I just don't get it but, in my mind, when an object in motion meets a stationary object, there is a lose of momentum thereby slowing down the acceleration process. Is this wrong? I'm still puzzled as to how the WTC towers collapsed at nearly the same time as an object in freefall would take to fall the same distance.

S.Macie, P.E.

See what's free at AOL.com.

RE: 9-11 Wackos

"increasing mass and acceleration" To be technically accurate, acceleration does not change. It is constant except that it is immeasurably higher at the foundation than at the penthouse due to its closer proximity to the center of mass of the Earth.

Mark E. Deardorff, S.E.

Structural Engineer

3434 4th Ave

San Diego, CA 92103

P 619.299.5550

F 619.299.9934

mdeardorff@burkett-wong.com

From: Gerard Madden, SE [mailto:gmse4603@gmail.com]
Sent: Friday, May 25, 2007 12:13 PM
To: seaint@seaint.org
Subject: Re: 9-11 Wackos

Exactly.

And remember, the resistance strength at each floor is constant. So as you go down the building, each floor has the same capacity to resist the pancacking, but the force cannot be overcome due to the ever increasing mass and acceleration to the point that it becomes neglible to momentarily slow down the fall.

-g

On 5/25/07, Christopher Wright <chrisw@skypoint.com> wrote:

> Maybe I just don't get it but, in my mind, when an object in motion
> meets a stationary object, there is a lose of momentum thereby
> slowing down the acceleration process.
Momentum is conserved in a collision, although energy may be
dissipated. If you think of each floor as a rigid body, the force of
impact acts to speed up the lower floor and slow down in upper floor,
such the mu1Vu1 = ml1Vl2+mu2Vu2. The upper floor will have to slow
down a little bit momentarily becasue it is subject to the reaction
of the force needed to break the support connections for the lower
floor.

Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw@skypoint.com   | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania
1864)
http://www.skypoint.com/~chrisw/

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*
*   This email was sent to you via Structural Engineers
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--
-gm

Re: 9-11 Wackos

Exactly.

And remember, the resistance strength at each floor is constant. So as you go down the building, each floor has the same capacity to resist the pancacking, but the force cannot be overcome due to the ever increasing mass and acceleration to the point that it becomes neglible to momentarily slow down the fall.

-g

On 5/25/07, Christopher Wright <chrisw@skypoint.com> wrote:

> Maybe I just don't get it but, in my mind, when an object in motion
> meets a stationary object, there is a lose of momentum thereby
> slowing down the acceleration process.
Momentum is conserved in a collision, although energy may be
dissipated. If you think of each floor as a rigid body, the force of
impact acts to speed up the lower floor and slow down in upper floor,
such the mu1Vu1 = ml1Vl2+mu2Vu2. The upper floor will have to slow
down a little bit momentarily becasue it is subject to the reaction
of the force needed to break the support connections for the lower
floor.

Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw@skypoint.com   | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania
1864)
http://www.skypoint.com/~chrisw/

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad@seaint.org . Remember, any email you
*   send to the list is public domain and may be re-posted
*   without your permission. Make sure you visit our web
*   site at: http://www.seaint.org
******* ****** ****** ****** ******* ****** ****** ********

--
-gm

Re: 9-11 Wackos

> Maybe I just don't get it but, in my mind, when an object in motion
> meets a stationary object, there is a lose of momentum thereby
> slowing down the acceleration process.
Momentum is conserved in a collision, although energy may be
dissipated. If you think of each floor as a rigid body, the force of
impact acts to speed up the lower floor and slow down in upper floor,
such the mu1Vu1 = ml1Vl2+mu2Vu2. The upper floor will have to slow
down a little bit momentarily becasue it is subject to the reaction
of the force needed to break the support connections for the lower
floor.

******* ****** ****** ****** ******* ****** ****** ********

Re: 9-11 Wackos

Momentum= MassxVelocity

In the the collapse, Mass increased at each floor and velocity was increasing as well

On 5/25/07, Gerard Madden, SE < gmse4603@gmail.com> wrote:

wouldn't it be gaining momentum at each floor? afterall, the shearing of the floor from the impact of the (oh I don't know say 20 stories of floor from above) takes a millisecond to break through...now when you reach the next floor with now 21 floors coming down there is that much more has to have to be stopped and the momentum resistance strength creates less and less drag due to the force increase (MASSxACCELERATION). Gravity is acting in the same direction as the movement of the mass, so it's not a text book example in college text book of perfect or idealized assumption of elasticity.

-gm

On 5/25/07, ECVAl3@aol.com <ECVAl3@aol.com> wrote:

In a message dated 5/25/2007 10:33:37 A.M. Pacific Daylight Time, gmse4603@gmail.com writes:

Freefall: mass and acceleration....an ever increasing mass (each floor falling on another) and acceleration (those things were too heavy to reach terminal speed from wind resistance) ...makes perfect sense to me.

Maybe I just don't get it but, in my mind, when an object in motion meets a stationary object, there is a lose of momentum thereby slowing down the acceleration process. Is this wrong? I'm still puzzled as to how the WTC towers collapsed at nearly the same time as an object in freefall would take to fall the same distance.

S.Macie, P.E.

See what's free at AOL.com.

--
-gm

--
-gm

Re: 9-11 Wackos

wouldn't it be gaining momentum at each floor? afterall, the shearing of the floor from the impact of the (oh I don't know say 20 stories of floor from above) takes a millisecond to break through...now when you reach the next floor with now 21 floors coming down there is that much more has to have to be stopped and the momentum resistance strength creates less and less drag due to the force increase (MASSxACCELERATION). Gravity is acting in the same direction as the movement of the mass, so it's not a text book example in college text book of perfect or idealized assumption of elasticity.

-gm

On 5/25/07, ECVAl3@aol.com <ECVAl3@aol.com> wrote:

In a message dated 5/25/2007 10:33:37 A.M. Pacific Daylight Time, gmse4603@gmail.com writes:

Freefall: mass and acceleration....an ever increasing mass (each floor falling on another) and acceleration (those things were too heavy to reach terminal speed from wind resistance) ...makes perfect sense to me.

Maybe I just don't get it but, in my mind, when an object in motion meets a stationary object, there is a lose of momentum thereby slowing down the acceleration process. Is this wrong? I'm still puzzled as to how the WTC towers collapsed at nearly the same time as an object in freefall would take to fall the same distance.

S.Macie, P.E.

See what's free at AOL.com.

--
-gm

Re: High lift grouting

Doug:

See section of CBC 2104A.6.1.1.3

Joe Venuti
Johnson & Nielsen Associates
Palm Springs, CA

See what's free at AOL.com.

RE: High lift grouting

Mark,

I agree, but my point is that I can’t find a statement supporting this in the code(s).

Thanks,

Doug Mayer, SE

Structural Engineer

TaylorTeter

Partnership

From: Mark E. Deardorff [mailto:mdeardorff@burkett-wong.com]
Sent: Friday, May 25, 2007 10:40 AM
To: seaint@seaint.org
Subject: RE: High lift grouting

How do they propose to remove debris from the three out of four cells that aren't open for inspection? Maybe I am wrong but I thought that is what "cleanouts" were for.

Mark E. Deardorff, S.E.

Structural Engineer

3434 4th Ave

San Diego, CA 92103

P 619.299.5550

F 619.299.9934

mdeardorff@burkett-wong.com

From: Doug Mayer [mailto:doug.mayer@taylorteter.com]
Sent: Friday, May 25, 2007 10:25 AM
To: seaint@seaint.org
Subject: High lift grouting

List,

I have a CMU wall building in Washington (state) being built that has fully grouted walls and reinforcing at 8” o.c. each way. The contractor wants to do high lift grouting in lieu of the low-lifts, which is fine with me. However, the topic of cleanouts has become an issue and I’m not sure of the correct answer.

They would like to do cleanouts at 32” o.c., but I know that older codes and the Concrete Masonry Association of California and Nevada specify that cleanouts are to occur at each vertical cell with reinforcing, or continuous special inspection is to be provided. But, looking at the IBC 2003 and ACI 530-02 – the codes for this project – I can’t seem to find any reference or specification for cleanout requirements. Any ideas?

Thanks for the help,

Doug Mayer, SE

Structural Engineer

TaylorTeter

Partnership

Re: 9-11 Wackos

In a message dated 5/25/2007 10:33:37 A.M. Pacific Daylight Time, gmse4603@gmail.com writes:

Freefall: mass and acceleration....an ever increasing mass (each floor falling on another) and acceleration (those things were too heavy to reach terminal speed from wind resistance) ...makes perfect sense to me.

S.Macie, P.E.

See what's free at AOL.com.

RE: High lift grouting

How do they propose to remove debris from the three out of four cells that aren't open for inspection? Maybe I am wrong but I thought that is what "cleanouts" were for.

Mark E. Deardorff, S.E.

Structural Engineer

3434 4th Ave

San Diego, CA 92103

P 619.299.5550

F 619.299.9934

mdeardorff@burkett-wong.com

From: Doug Mayer [mailto:doug.mayer@taylorteter.com]
Sent: Friday, May 25, 2007 10:25 AM
To: seaint@seaint.org
Subject: High lift grouting

List,

I have a CMU wall building in Washington (state) being built that has fully grouted walls and reinforcing at 8” o.c. each way. The contractor wants to do high lift grouting in lieu of the low-lifts, which is fine with me. However, the topic of cleanouts has become an issue and I’m not sure of the correct answer.

They would like to do cleanouts at 32” o.c., but I know that older codes and the Concrete Masonry Association of California and Nevada specify that cleanouts are to occur at each vertical cell with reinforcing, or continuous special inspection is to be provided. But, looking at the IBC 2003 and ACI 530-02 – the codes for this project – I can’t seem to find any reference or specification for cleanout requirements. Any ideas?

Thanks for the help,

Doug Mayer, SE

Structural Engineer

TaylorTeter

Partnership

Re: 9-11 Wackos

My understanding of controlled demolition is that the charges do not go off simultaneously. It's "CONTROLLED" to minimize debris spread. So first explosion to the beginning time of global failure may take a matter of seconds.

Look at the Seattle Kingdome implosion....you see a bunch of explosion ring around the building, then a few seconds later, it begins to collapse and falls pretty quickly one that process begins.

Mr. Robertson's design of the World Trade Center saved thousands of lives. Without the luxuries we have today of sophisticated software to model collaspe scenarious I might add.

Yeah other big name engineers (who are in direct competition for the same types of projects) have stated they would have done things different and their designs would have stood up longer or not have collapsed. But that's hindsight isn't it?

IF we can stop people from flying planes into buildings, maybe that would be a good way to approach designing a safe high rise. I dunno, just a thought.

Freefall: mass and acceleration....an ever increasing mass (each floor falling on another) and acceleration (those things were too heavy to reach terminal speed from wind resistance) ...makes perfect sense to me.

-g

On 5/25/07, ECVAl3@aol.com <ECVAl3@aol.com> wrote:

I've seen some of the videos mentioned here and I agree there is a lot of ways to manipulate media to bias public reaction. This is proven everyday in television news broadcasts and newspapers.

The only thing that really haunts me is, with a controlled demolition, the 37 story Sands Hotel in Las Vegas took 17 seconds to completely collapse. With the pancake theory, the 77 story Twin Towers took 9 to 14 seconds to collapse. Does this mean that it is not possible to safely design and engineer tall buildings? What are the limits in height we should be considering in the future to insure the life-health safety issues? Didn't the engineers of the Twin Towers design with due diligence or is this kind of collapse, regardless of the cause, acceptable because of economic or other reasons?

S.Macie, P.E.

See what's free at AOL.com.

--
-gm