Structural Engineering: 2009-01-25

Saturday, January 31, 2009

RE: Concrete Spring Constant for Base Plate Modeling

John,
I would suggest the procedure in Omer Blodgett's "Design of Welded Structures". It accounts for the stretch in the anchor rods and the strain in the concrete. As with all of his work, it is very logically presented and well thought.

It is easily presented in a MathCAD template.

Regards, Harold Sprague

Date: Fri, 30 Jan 2009 11:22:07 -0800
Subject: Re: Concrete Spring Constant for Base Plate Modeling
From: jeongidea@gmail.com
To: seaint@seaint.org

Hmm, just pick the number. However, the question is what is the reasonable number.

Depending on spring constant, it will change tensions on the anchor bolts. If somebody starts with no idea of bolts' tensions, they may come up with very small number if they use very flexible springs.

Anyway, the reason that I am modeling the base plate instead of using AISC design guide is my base plate has re-entrant corner inside and have both direction lateral loads (of course both direction shears and moments) at the same time.

I want to know how much stress concentrations at the re-entrant corners are and I don't think AISC design guide covers this situation.

Thank you so much.

John

On Fri, Jan 30, 2009 at 10:42 AM, David Fisher <dfisher@fpse.com> wrote:

Hooke's Law is bascially F = k*x

F, I assume you know.

x = say 0.1" just to pick a value, solve for "K" which is your spring constant.

Not sure what your structure/foundation type is or load magnitudes…

That's a good place to start, if the results don't make sense, then reduce the value of "x" as necessary
To make the results reasonable.

The bigger question might be, why are you modelling this condition this way?
AISC has spent years developing the base plate design criteria.

Can't you just use that design procedure?

From: john yang [mailto:jeongidea@gmail.com]
Sent: Friday, January 30, 2009 12:38 PM
To: seaint@seaint.org
Subject: Re: Concrete Spring Constant for Base Plate Modeling

How can I assume "the extension"? For spring, k=EA/L I know E and I know A and I know concrete compressive strain (0.003). The problem is L or deltaL. How can I assume those? Will L be full length or depth of member? How much will I assume delta L for it?

Thank you so much.

John

On Fri, Jan 30, 2009 at 9:31 AM, David Fisher <dfisher@fpse.com> wrote:

Try my favorite formula, the foundation for structural engineering:

Hooke's Law:

"as the extension, so the force…"

David L. Fisher SE PE

Fisher and Partners - Cayman
372 West Ontario Chicago 60610
75 Fort Street Georgetown Grand Cayman BWI
319 A Street Boston 02210

312.573.1701
312.573.1726 facsimile
312.622.0409 mobile

www.fpse.com

From: john yang [mailto:jeongidea@gmail.com]
Sent: Friday, January 30, 2009 11:29 AM
To: seaint@seaint.org
Subject: Concrete Spring Constant for Base Plate Modeling

Hi,
I am modeling base plate on the 6000 psi concrete column and I want to put concrete compression only spring to represent concrete. The problem is what is the compressive spring constant of concrete. Could you help me to get it?

Thank you so much.

John

Windows Live™: E-mail. Chat. Share. Get more ways to connect. Check it out.

Re: thor's pool

Not to mention Triton of the Inhumans making a guest appearance...

David Fisher wrote:
>
> Good advice, sir…
>
> "Thor's pool"….sounds like he should be battling Namor for control of
> the Deep.
>
> J
>
> David L. Fisher SE PE
>
> Fisher and Partners - Cayman
>
> 372 West Ontario Chicago 60610
>
> 75 Fort Street Georgetown Grand Cayman BWI
>
> 319 A Street Boston 02210
>
> 312.573.1701
>
> 312.573.1726 facsimile
>
> 312.622.0409 mobile
>
> www.fpse.com
>
> ------------------------------------------------------------------------
>
> *From:* Andrew Kester, PE [mailto:akester@cfl.rr.com]
> *Sent:* Saturday, January 31, 2009 11:43 AM
> *To:* seaint@seaint.org
> *Subject:* re: thor's pool
>
> Thor,
>
> I think you have several things to consider with this project, which
> you may already be doing. The existing foundations of the house if
> within a certain distance (and depending on your soil) will put a
> lateral suracharge load on the wall of the pool. Also, you may have to
> give the contractor some shoring direction to avoid settlement issues
> with the existing house. I would include a preliminary site visit to
> review the existing wall and take lots of photographs and document any
> exterior and interior cracks, just in case down the road they start
> making lots of claims. I don't know the existing home construciton.
>
> Also, in Florida, it would be very unusual I think to use the concrete
> deck as an apron. These are typically placed after the entire project
> is done, and are simply a slab-on-grade with a textured "cool-deck"
> topping. More popular now is the use of concrete pavers. If the owner
> wants a concrete deck and you can get them to OK your idea, then I
> would certainly explain to them this is structural element and cannot
> be removed ever (and note that on your dwgs). You may want to recess
> the structural concrete apron a few inches from the finished top edge
> of the pool so they can place a non-structural cool-deck topping or
> even a layer of sand and thin pavers.
>
> My conclusion as well as any others (as previously stated) on this
> list is pool design is not an exact science, but somewhat of a mix of
> science and art. If the pool is non-rectangular it will behave more
> like a circular water tank and the pool water will balance out the
> soil pressure and put the reinforcement in tension. But I don't see
> how in a rectangular pool the walls, at least while being constructed
> and empty, do not act like cantilevered walls.
>
> And I have seen several pools pop out of the ground when partially
> emptied during a storm event because of a high water table. One was up
> two feet and took the deck with it, the whole thing was a total loss.
> As mentioned by others, they do have valves that are supposed to pop
> and allow groundwater to enter the pool to balance the hyrdostatic
> pressure. But if you design it not to float in the empty condition
> with a high water table, and simply add mass in the form of lots of
> concrete, I would expect you will have a very angry homeowner and
> contractor...
>
> Conclusion- I don't touch swimming pools, seems like a no-win. Good
> luck, and let us know what you come up with.
>
> "I guess i should. i'm in soft rock and th 9' end is against the ex.
> house:
> ...
> Thor
>
> HTH,
>
> Andrew Kester, P.E.
> Orlando, Florida
>

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

Re: Thanks on Shear Flow Ps: digest mode is crap

> From: "Paul Guthrie" <PGuthrie@simivalley.org>

> Apologies if this has already been answered--I'm in digest mode, so a day =
> behind everyone, PLUS the digests do funny things with equal signs and =
> such and I really can't make sense out of anyone else's equations.

Actually, the Digest consolidator is probably not doing anything to the
message. The "=" precedes an ASCII code (typically 2 characters) for
non-alphanumeric characters or controls that are embedded in HTML coded
emails (e.g. line feed, quotes, etc.). The message is added to the Digest
complete with embedded codes since some digest readers may be able to
distinguish these and reproduce the correctly formatted text. If you are
reading the raw (ASCII) digest format with Outlook, you are stuck.

There are certain contributors to the list who have email settings that
cause their messages to be displayed completely in non-ASCII code in Digest
format and therefore, completely illegible. Not wrong, just a shortcoming of
your mail reader software when attempting to deal with Digests.

Regards
Paul
--
Paul Ransom, P.Eng.
ph 905 639-9628
fax 905 639-3866
ad026@hwcn.org

RE: thor's pool

... but I'm winning :^)

-----Original Message-----
From: David Fisher [mailto:dfisher@fpse.com]
Sent: Saturday, January 31, 2009 10:01 AM
To: seaint@seaint.org
Subject: RE: thor's pool

Good advice, sir…

“Thor’s pool”….sounds like he should be battling Namor for control of the Deep.

J

David L. Fisher SE PE

Fisher and Partners - Cayman

372 West Ontario Chicago 60610

75 Fort Street Georgetown Grand Cayman BWI

319 A Street Boston 02210

312.573.1701

312.573.1726 facsimile

312.622.0409 mobile

www.fpse.com

From: Andrew Kester, PE [mailto:akester@cfl.rr.com]
Sent: Saturday, January 31, 2009 11:43 AM
To: seaint@seaint.org
Subject: re: thor's pool

Thor,

I think you have several things to consider with this project, which you may already be doing. The existing foundations of the house if within a certain distance (and depending on your soil) will put a lateral suracharge load on the wall of the pool. Also, you may have to give the contractor some shoring direction to avoid settlement issues with the existing house. I would include a preliminary site visit to review the existing wall and take lots of photographs and document any exterior and interior cracks, just in case down the road they start making lots of claims. I don't know the existing home construciton.

Also, in Florida, it would be very unusual I think to use the concrete deck as an apron. These are typically placed after the entire project is done, and are simply a slab-on-grade with a textured "cool-deck" topping. More popular now is the use of concrete pavers. If the owner wants a concrete deck and you can get them to OK your idea, then I would certainly explain to them this is structural element and cannot be removed ever (and note that on your dwgs). You may want to recess the structural concrete apron a few inches from the finished top edge of the pool so they can place a non-structural cool-deck topping or even a layer of sand and thin pavers.

My conclusion as well as any others (as previously stated) on this list is pool design is not an exact science, but somewhat of a mix of science and art. If the pool is non-rectangular it will behave more like a circular water tank and the pool water will balance out the soil pressure and put the reinforcement in tension. But I don't see how in a rectangular pool the walls, at least while being constructed and empty, do not act like cantilevered walls.

And I have seen several pools pop out of the ground when partially emptied during a storm event because of a high water table. One was up two feet and took the deck with it, the whole thing was a total loss. As mentioned by others, they do have valves that are supposed to pop and allow groundwater to enter the pool to balance the hyrdostatic pressure. But if you design it not to float in the empty condition with a high water table, and simply add mass in the form of lots of concrete, I would expect you will have a very angry homeowner and contractor...

Conclusion- I don't touch swimming pools, seems like a no-win. Good luck, and let us know what you come up with.

"I guess i should. i'm in soft rock and th 9' end is against the ex. house:
...
Thor

HTH,

Andrew Kester, P.E.
Orlando, Florida

RE: thor's pool

Hi Andrew.

Thanks for your comments. And thanks to all the other feeds back to me. Yes, I have taken into account most of the issues that have been highlighted. They have alerted me to some of the secondary details that I wished to not overlook.

The "soil" is a fractured "soft" rock - the sort of rock that is stable and competent, with good bearing values, when undisturbed but will reduce to rubble if broken up/down. The pool is to be located adjacent to the ex. house foundation so, except for the nominal gap between (to make sure they are separate), the walls shouldn't have significant lateral loads (the wall of the house is/was a basement wall (full hght). Similarly, looking at the rock exposed, I don't think there is a settlement problem (but I take note of your caution) and I know that ground water will not be an issue. The site is at the top of a rise.

The "apron" idea is nothing more that a stiffening element to the pool wall and would only be a couple of feet wide at the most, however, I like your comment to lower that to allow for an extended walkway. At the moment I have designed the walls for both cantilever and top restrained conditions, as well as allowed for the full/empty condition.

I have been advised that if a pool contractor is employed, then that contractor will probably have a preferred method/detail so I expect to be working together with whomever is chosen by the Client.

Thanks to everyone (I love this list) and, yes, I guess if anyone wants to see the final result, I'd be happy to share it. My international peer review committee ... :^)

Thor A. Tandy P.Eng, C.Eng, Struct.Eng, MIStructE
Victoria, BC
Canada

-----Original Message-----
From: Andrew Kester, PE [mailto:akester@cfl.rr.com]
Sent: Saturday, January 31, 2009 9:43 AM
To: seaint@seaint.org
Subject: re: thor's pool

Thor,

I think you have several things to consider with this project, which you may already be doing. The existing foundations of the house if within a certain distance (and depending on your soil) will put a lateral suracharge load on the wall of the pool. Also, you may have to give the contractor some shoring direction to avoid settlement issues with the existing house. I would include a preliminary site visit to review the existing wall and take lots of photographs and document any exterior and interior cracks, just in case down the road they start making lots of claims. I don't know the existing home construciton.

Also, in Florida, it would be very unusual I think to use the concrete deck as an apron. These are typically placed after the entire project is done, and are simply a slab-on-grade with a textured "cool-deck" topping. More popular now is the use of concrete pavers. If the owner wants a concrete deck and you can get them to OK your idea, then I would certainly explain to them this is structural element and cannot be removed ever (and note that on your dwgs). You may want to recess the structural concrete apron a few inches from the finished top edge of the pool so they can place a non-structural cool-deck topping or even a layer of sand and thin pavers.

My conclusion as well as any others (as previously stated) on this list is pool design is not an exact science, but somewhat of a mix of science and art. If the pool is non-rectangular it will behave more like a circular water tank and the pool water will balance out the soil pressure and put the reinforcement in tension. But I don't see how in a rectangular pool the walls, at least while being constructed and empty, do not act like cantilevered walls.

And I have seen several pools pop out of the ground when partially emptied during a storm event because of a high water table. One was up two feet and took the deck with it, the whole thing was a total loss. As mentioned by others, they do have valves that are supposed to pop and allow groundwater to enter the pool to balance the hyrdostatic pressure. But if you design it not to float in the empty condition with a high water table, and simply add mass in the form of lots of concrete, I would expect you will have a very angry homeowner and contractor...

Conclusion- I don't touch swimming pools, seems like a no-win. Good luck, and let us know what you come up with.

"I guess i should. i'm in soft rock and th 9' end is against the ex. house:
...
Thor

HTH,

Andrew Kester, P.E.
Orlando, Florida

RE: thor's pool

Good advice, sir…

“Thor’s pool”….sounds like he should be battling Namor for control of the Deep.

David L. Fisher SE PE

Fisher and Partners - Cayman

372 West Ontario Chicago 60610

75 Fort Street Georgetown Grand Cayman BWI

319 A Street Boston 02210

312.573.1701

312.573.1726 facsimile

312.622.0409 mobile

www.fpse.com

From: Andrew Kester, PE [mailto:akester@cfl.rr.com]
Sent: Saturday, January 31, 2009 11:43 AM
To: seaint@seaint.org
Subject: re: thor's pool

Thor,

I think you have several things to consider with this project, which you may already be doing. The existing foundations of the house if within a certain distance (and depending on your soil) will put a lateral suracharge load on the wall of the pool. Also, you may have to give the contractor some shoring direction to avoid settlement issues with the existing house. I would include a preliminary site visit to review the existing wall and take lots of photographs and document any exterior and interior cracks, just in case down the road they start making lots of claims. I don't know the existing home construciton.

Also, in Florida, it would be very unusual I think to use the concrete deck as an apron. These are typically placed after the entire project is done, and are simply a slab-on-grade with a textured "cool-deck" topping. More popular now is the use of concrete pavers. If the owner wants a concrete deck and you can get them to OK your idea, then I would certainly explain to them this is structural element and cannot be removed ever (and note that on your dwgs). You may want to recess the structural concrete apron a few inches from the finished top edge of the pool so they can place a non-structural cool-deck topping or even a layer of sand and thin pavers.

My conclusion as well as any others (as previously stated) on this list is pool design is not an exact science, but somewhat of a mix of science and art. If the pool is non-rectangular it will behave more like a circular water tank and the pool water will balance out the soil pressure and put the reinforcement in tension. But I don't see how in a rectangular pool the walls, at least while being constructed and empty, do not act like cantilevered walls.

And I have seen several pools pop out of the ground when partially emptied during a storm event because of a high water table. One was up two feet and took the deck with it, the whole thing was a total loss. As mentioned by others, they do have valves that are supposed to pop and allow groundwater to enter the pool to balance the hyrdostatic pressure. But if you design it not to float in the empty condition with a high water table, and simply add mass in the form of lots of concrete, I would expect you will have a very angry homeowner and contractor...

Conclusion- I don't touch swimming pools, seems like a no-win. Good luck, and let us know what you come up with.

"I guess i should. i'm in soft rock and th 9' end is against the ex. house:
...
Thor

HTH,

Andrew Kester, P.E.
Orlando, Florida

re: thor's pool

BEGIN:VCARD
VERSION:2.1
N:Andrew Kester;PE
FN:Andrew Kester, PE
EMAIL;PREF;INTERNET:akester@cfl.rr.com
REV:20090131T174243Z
END:VCARD

Thor,

Conclusion- I don't touch swimming pools, seems like a no-win. Good luck, and let us know what you come up with.

"I guess i should. i'm in soft rock and th 9' end is against the ex. house:
...
Thor

HTH,

Andrew Kester, P.E.
Orlando, Florida

Re: Facing mistakes in structural design

You got me!
Gary

David Topete wrote:
> It's a quote from a movie. Guess the movie.
>
> On Fri, Jan 30, 2009 at 7:34 AM, David Topete <d.topete73@gmail.com
> <mailto:d.topete73@gmail.com>> wrote:
>
> "What's a widget?"
>
>
> On Fri, Jan 30, 2009 at 4:48 AM, Gary L. Hodgson and Assoc.
> <design@hodgsoneng.ca <mailto:design@hodgsoneng.ca>> wrote:
>
> Toot away. We all need those feel good moments to compensate
> for those other times when you wake up in the middle of the
> night and say did I forget to framitize the widget.
> Gary
>
>
> Rhkratzse@aol.com <mailto:Rhkratzse@aol.com> wrote:
>
> IIRC it was a grad student, and since this was 20+/- yrs
> ago they're probably at the top of their profession by now.
>
> My memory is that the critical thing is that the Citicorp
> building has only 4 columns around the perimeter, but
> they're not at the corners, they're in the middle of each
> side. The design, again IIRC, was based on analyses in
> the X-X and Y-Y directions, but not in the diagonal
> direction, which is what the student caught.
>
> Not to toot my own horn, but in 1965 or '66, on my very
> first engineering job, I was figuring the loads due to a
> four-legged traveling crane and I came to the conclusion
> that diagonal forces controlled, just as they did in the
> Citicorp building's columns.
>
> Ralph Hueston Kratz, S.E.
> Richmond CA USA
>
> In a message dated 1/29/09 7:30:58 PM,
> seaint04@lewisengineering.com
> <mailto:seaint04@lewisengineering.com> writes:
>
> I'm wondering who that student was and what is he/she
> doing today?
>
> Rich
>
>
> -----Original Message-----
> From: David Fisher [mailto:dfisher@fpse.com
> <mailto:dfisher@fpse.com>]
> Sent: Thursday, January 29, 2009 11:09 AM
> To: seaint@seaint.org <mailto:seaint@seaint.org>
> Subject: RE: Facing mistakes in structural design
>
> Jorge:
>
> That was the Citicorp Center in New York:
>
> http://www.duke.edu/~hpgavin/ce131/citicorp1.htm
> <http://www.duke.edu/%7Ehpgavin/ce131/citicorp1.htm>
>
>
> Fascinating article...
>
>
>
> David L. Fisher SE PE
> International Project Manager
> The Food Water Energy Company/movewithus international
> Trinity House
> Cambridge Business Park
> Cambridge CB4 0WZ
> United Kingdom
>
> 312.622.0409 GSM mobile
>
> THE FOOD WATER & ENERGY COMPANY
>
>
>
>
>
>
>
> -----Original Message-----
> From: Jorge Jimenez [mailto:joraljim@prtc.net
> <mailto:joraljim@prtc.net>]
> Sent: Thursday, January 29, 2009 11:08 AM
> To: seaint@seaint.org <mailto:seaint@seaint.org>
> Subject: Facing mistakes in structural design
>
> I remember a story of a group of graduate students
> that found a design flaw
> in a high-rise building for wind effects
> considerations. They called the
> attention to the structural engineer who made the
> design. The designer, a
> renowned structural engineer, courageously disclosed
> to the public his
> mistake. The building was in use and then needed an
> important retrofitting.
> Do you remember the name of this structural engineer
> or have knowledge of
> similar and recognized circumstances?
>
> Jorge Jimenez, PE
>
>
>
>
> **************
> Know Your Numbers: Get tips and tools to help you improve
> your credit score.
> (http://www.walletpop.com/credit/credit-reports?ncid=emlcntuswall00000002)
>
>
> ******* ****** ******* ******** ******* ******* ******* ***
> * 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
> <mailto: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 ******* ****** ****** ****** *******
> ****** ****** ********
>
>
>
>
> --
> David Topete, SE
>
>
>
>
> --
> David Topete, SE

Friday, January 30, 2009

RE: Concrete Spring Constant for Base Plate Modeling

Wesley, that was a great link. How can I get more like that?

- Jeremy

Quoting Wesley Werner <wwerner@conewago.com>:

> John,
>
> Try this link
> http://www.aisc.org/UploadedContent/2008NASCCSessions/E1/default.htm . A
> few slides into the presentation the presenter talks about spring
> constants. He concludes that for 3,000 psi concrete the value is about
> 1,000,000 lb/in. For 3,000 psi grout the value would be 2,000,000 psi.
>
>
> Wesley C. Werner
>
>
>
>
> ________________________________
>
> From: john yang [mailto:jeongidea@gmail.com]
> Sent: Friday, January 30, 2009 2:22 PM
> To: seaint@seaint.org
> Subject: Re: Concrete Spring Constant for Base Plate Modeling
>
>
> Hmm, just pick the number. However, the question is what is the
> reasonable number.
>
> Depending on spring constant, it will change tensions on the anchor
> bolts. If somebody starts with no idea of bolts' tensions, they may
> come up with very small number if they use very flexible springs.
>
> Anyway, the reason that I am modeling the base plate instead of using
> AISC design guide is my base plate has re-entrant corner inside and have
> both direction lateral loads (of course both direction shears and
> moments) at the same time.
>
> I want to know how much stress concentrations at the re-entrant corners
> are and I don't think AISC design guide covers this situation.
>
> Thank you so much.
>
> John
>
>
> On Fri, Jan 30, 2009 at 10:42 AM, David Fisher <dfisher@fpse.com> wrote:
>
>
>
>
> Hooke's Law is bascially F = k*x
>
>
>
> F, I assume you know.
>
>
>
> x = say 0.1" just to pick a value, solve for "K" which is your
> spring constant.
>
>
>
> Not sure what your structure/foundation type is or load
> magnitudes...
>
>
>
> That's a good place to start, if the results don't make sense,
> then reduce the value of "x" as necessary
>
> To make the results reasonable.
>
>
>
> The bigger question might be, why are you modelling this
> condition this way?
>
> AISC has spent years developing the base plate design criteria.
>
>
>
> Can't you just use that design procedure?
>
>
>
>
>
>
> ________________________________
>
>
> From: john yang [mailto:jeongidea@gmail.com]
> Sent: Friday, January 30, 2009 12:38 PM
> To: seaint@seaint.org
> Subject: Re: Concrete Spring Constant for Base Plate Modeling
>
>
>
> How can I assume "the extension"? For spring, k=EA/L I know E
> and I know A and I know concrete compressive strain (0.003). The
> problem is L or deltaL. How can I assume those? Will L be full length
> or depth of member? How much will I assume delta L for it?
>
> Thank you so much.
>
> John
>
> On Fri, Jan 30, 2009 at 9:31 AM, David Fisher <dfisher@fpse.com>
> wrote:
>
> Try my favorite formula, the foundation for structural
> engineering:
>
>
>
> Hooke's Law:
>
>
>
> "as the extension, so the force..."
>
>
>
>
>
>
>
>
>
> David L. Fisher SE PE
>
>
>
> Fisher and Partners - Cayman
>
> 372 West Ontario Chicago 60610
>
> 75 Fort Street Georgetown Grand Cayman BWI
>
> 319 A Street Boston 02210
>
>
>
> 312.573.1701
>
> 312.573.1726 facsimile
>
> 312.622.0409 mobile
>
>
>
> www.fpse.com
>
>
>
>
> ________________________________
>
>
> From: john yang [mailto:jeongidea@gmail.com]
> Sent: Friday, January 30, 2009 11:29 AM
> To: seaint@seaint.org
> Subject: Concrete Spring Constant for Base Plate Modeling
>
>
>
> Hi,
> I am modeling base plate on the 6000 psi concrete column and I
> want to put concrete compression only spring to represent concrete. The
> problem is what is the compressive spring constant of concrete. Could
> you help me to get it?
>
> Thank you so much.
>
> John
>
>
>
>
>

RE: Facing mistakes in structural design

I have read an article in a magazine about this. The designer was right in
disclosing the error which resulted in retrofitting the building before a
big storm came. That building was not damaged by the storm.

An Architect once asked me to use one way reinforcing on a suspended slab
which qualifies as a two way slab, I was a new engineer then so I complied.
When the building was constructed, the contractor, who is also educated as
a structural engineer informed me of my mistake so additional reinforcing
was added in the perpendicular direction which prevented cracking on
corners.

I think if the truth will save lives then people concerned should know about
it.

Alex C. Nacionales
Vancouver, Canada

-----Original Message-----
From: Jorge Jimenez [mailto:joraljim@prtc.net]
Sent: Thursday, January 29, 2009 9:08 AM
To: seaint@seaint.org
Subject: Facing mistakes in structural design

I remember a story of a group of graduate students that found a design flaw
in a high-rise building for wind effects considerations. They called the
attention to the structural engineer who made the design. The designer, a
renowned structural engineer, courageously disclosed to the public his
mistake. The building was in use and then needed an important retrofitting.
Do you remember the name of this structural engineer or have knowledge of
similar and recognized circumstances?

Jorge Jimenez, PE

Re: Certified Fire Protection

Let's see if I understand this correctly. An employee for the Indian
Chief Fire Co. (see email address indianchief.fireco@live.com )
recommends his own company. Only a minor conflict of interest..........

I plan to respond to him directly.

Michael Hixson wrote:
> I recommend this company for any services pertaining to
> Fire Extinguishers, Fire Sprinkler Systems, Fire Alarms, Hood
> suppression systems
> They have certified techs and licensed contractors to do the job
> If any of you fellow engineers need the resource
> the number is
>
> Indian Chief Fire Co. (818)500-0106
>
>
> ------------------------------------------------------------------------
> Windows Live™ Hotmail®…more than just e-mail. See how it works.
> <http://windowslive.com/howitworks?ocid=TXT_TAGLM_WL_t2_hm_justgotbetter_howitworks_012009>

Certified Fire Protection

I recommend this company for any services pertaining to
Fire Extinguishers, Fire Sprinkler Systems, Fire Alarms, Hood suppression systems
They have certified techs and licensed contractors to do the job
If any of you fellow engineers need the resource
the number is

Indian Chief Fire Co. (818)500-0106

Windows Live™ Hotmail®…more than just e-mail. See how it works.

Re: IBC Section 1908.1.16 is a bugger

Yeah, But if the anchor fails in concrete breakout or pullout, I don't think we can eliminate 2.5 factor. Unfortunately, so many cases are failed in the concrete not anchor steel. Concrete is not ductile material.

So if I use overstrength factor, do you think I still use 2.5 factor?

John

On Fri, Jan 30, 2009 at 12:07 PM, <coengineer@aim.com> wrote:

Bill,

IIRC, D.3.3.4 and D.3.3.5 in Appendix D require that there is ductile failure, otherwise the anchorage is not permitted. The idea behind the 2.5 factor is if you can provide enough overstrength in the anchorage that there is little chance of failure, you don't have to have a ductile connection. Think equipment bracing anchors on a shallow slab.

If you are doing hold downs, how about using a smaller diameter rod that will get ductile faulure, and put a plate washer in the seat of the hold down. We see this all of the time with our DUC Undercut anchors for tilt up retrofits.

HTH,

Howard Silverman, PE
Anchoring Systems and Field Engineer Manager
USP Structural Connectors
hsilverman@uspconnectors.com

www.USPconnectors.com

-----Original Message-----
From: Bill Allen <t.w.allen@cox.net>
To: seaint@seaint.org
Sent: Fri, 30 Jan 2009 11:15 am
Subject: RE: IBC Section 1908.1.16 is a bugger

Yes, I am in California.

I am referring to structural components, specifically hold downs in residential shear walls in remodels.

One plan checker I am currently dealing with won't even let me use 2,500 psi concrete. The Simpson program will not work for 2,000 psi concrete. I don't think the plan checker could tell me the difference between 2,000 psi concrete and 2,500 psi concrete except for a number in a specification. Both are uninspected.

I asked him if he knew where the 2.5 factor came from. He said "Yes. It came from the code".

Doh!

Yes, he's a S.E.

Sigh...

T. William (Bill) Allen, S.E.

ALLEN DESIGNS

Consulting Structural Engineers
V (949) 248-8588 • F(949) 209-2509

-----Original Message-----
From: john yang [mailto:jeongidea@gmail.com]
Sent: Friday, January 30, 2009 10:43 AM
To: seaint@seaint.org
Subject: Re: IBC Section 1908.1.16 is a bugger

I know 2.5 factor killing especially non-structural component case. I don't know you are in California or not. However, In California Building Code, we have some relaxation for non-structural component members. If your are located in California, see 1908A.1.47.

John

On Fri, Jan 30, 2009 at 10:26 AM, Bill Allen <t.w.allen@cox.net> wrote:

Now that new construction is slowing down, I wonder how big of a role this will play in the remodel world.

Does anyone know the source of the 2.5 factor mentioned in the modification to ACI 318 Appendix D.3.3.5? It seems rather arbitrary to me. But, what do I know?

T. William (Bill) Allen, S.E.

ALLEN DESIGNS

Consulting Structural Engineers
V (949) 248-8588 • F(949) 209-2509

A Good Credit Score is 700 or Above. See yours in just 2 easy steps!

RE: Concrete Spring Constant for Base Plate Modeling (correction)

Make that 6,000 psi grout.

Wesley C. Werner

From: Wesley Werner [mailto:wwerner@conewago.com]
Sent: Friday, January 30, 2009 2:55 PM
To: seaint@seaint.org
Subject: RE: Concrete Spring Constant for Base Plate Modeling

John,

Try this link http://www.aisc.org/UploadedContent/2008NASCCSessions/E1/default.htm . A few slides into the presentation the presenter talks about spring constants. He concludes that for 3,000 psi concrete the value is about 1,000,000 lb/in. For 3,000 psi grout the value would be 2,000,000 psi.

Wesley C. Werner

From: john yang [mailto:jeongidea@gmail.com]
Sent: Friday, January 30, 2009 2:22 PM
To: seaint@seaint.org
Subject: Re: Concrete Spring Constant for Base Plate Modeling

Hmm, just pick the number. However, the question is what is the reasonable number.

Depending on spring constant, it will change tensions on the anchor bolts. If somebody starts with no idea of bolts' tensions, they may come up with very small number if they use very flexible springs.

Anyway, the reason that I am modeling the base plate instead of using AISC design guide is my base plate has re-entrant corner inside and have both direction lateral loads (of course both direction shears and moments) at the same time.

I want to know how much stress concentrations at the re-entrant corners are and I don't think AISC design guide covers this situation.

Thank you so much.

John

On Fri, Jan 30, 2009 at 10:42 AM, David Fisher <dfisher@fpse.com> wrote:

Hooke's Law is bascially F = k*x

F, I assume you know.

x = say 0.1" just to pick a value, solve for "K" which is your spring constant.

Not sure what your structure/foundation type is or load magnitudes…

That's a good place to start, if the results don't make sense, then reduce the value of "x" as necessary

To make the results reasonable.

The bigger question might be, why are you modelling this condition this way?

AISC has spent years developing the base plate design criteria.

Can't you just use that design procedure?

From: john yang [mailto:jeongidea@gmail.com]
Sent: Friday, January 30, 2009 12:38 PM
To: seaint@seaint.org
Subject: Re: Concrete Spring Constant for Base Plate Modeling

How can I assume "the extension"? For spring, k=EA/L I know E and I know A and I know concrete compressive strain (0.003). The problem is L or deltaL. How can I assume those? Will L be full length or depth of member? How much will I assume delta L for it?

Thank you so much.

John

On Fri, Jan 30, 2009 at 9:31 AM, David Fisher <dfisher@fpse.com> wrote:

Try my favorite formula, the foundation for structural engineering:

Hooke's Law:

"as the extension, so the force…"

David L. Fisher SE PE

Fisher and Partners - Cayman

372 West Ontario Chicago 60610

75 Fort Street Georgetown Grand Cayman BWI

319 A Street Boston 02210

312.573.1701

312.573.1726 facsimile

312.622.0409 mobile

www.fpse.com

From: john yang [mailto:jeongidea@gmail.com]
Sent: Friday, January 30, 2009 11:29 AM
To: seaint@seaint.org
Subject: Concrete Spring Constant for Base Plate Modeling

Hi,
I am modeling base plate on the 6000 psi concrete column and I want to put concrete compression only spring to represent concrete. The problem is what is the compressive spring constant of concrete. Could you help me to get it?

Thank you so much.

John

Re: IBC Section 1908.1.16 is a bugger

Bill,

IIRC, D.3.3.4 and D.3.3.5 in Appendix D require that there is ductile failure, otherwise the anchorage is not permitted. The idea behind the 2.5 factor is if you can provide enough overstrength in the anchorage that there is little chance of failure, you don't have to have a ductile connection. Think equipment bracing anchors on a shallow slab.

If you are doing hold downs, how about using a smaller diameter rod that will get ductile faulure, and put a plate washer in the seat of the hold down. We see this all of the time with our DUC Undercut anchors for tilt up retrofits.

HTH,

Howard Silverman, PE
Anchoring Systems and Field Engineer Manager
USP Structural Connectors
hsilverman@uspconnectors.com

www.USPconnectors.com

-----Original Message-----
From: Bill Allen <t.w.allen@cox.net>
To: seaint@seaint.org
Sent: Fri, 30 Jan 2009 11:15 am
Subject: RE: IBC Section 1908.1.16 is a bugger

Yes, I am in California.

I am referring to structural components, specifically hold downs in residential shear walls in remodels.

One plan checker I am currently dealing with won't even let me use 2,500 psi concrete. The Simpson program will not work for 2,000 psi concrete. I don't think the plan checker could tell me the difference between 2,000 psi concrete and 2,500 psi concrete except for a number in a specification. Both are uninspected.

I asked him if he knew where the 2.5 factor came from. He said "Yes. It came from the code".

Doh!

Yes, he's a S.E.

Sigh...

T. William (Bill) Allen, S.E.

ALLEN DESIGNS

Consulting Structural Engineers
V (949) 248-8588 • F(949) 209-2509

-----Original Message-----
From: john yang [mailto:jeongidea@gmail.com]
Sent: Friday, January 30, 2009 10:43 AM
To: seaint@seaint.org
Subject: Re: IBC Section 1908.1.16 is a bugger

I know 2.5 factor killing especially non-structural component case. I don't know you are in California or not. However, In California Building Code, we have some relaxation for non-structural component members. If your are located in California, see 1908A.1.47.

John

On Fri, Jan 30, 2009 at 10:26 AM, Bill Allen <t.w.allen@cox.net> wrote:

Now that new construction is slowing down, I wonder how big of a role this will play in the remodel world.

Does anyone know the source of the 2.5 factor mentioned in the modification to ACI 318 Appendix D.3.3.5? It seems rather arbitrary to me. But, what do I know?

T. William (Bill) Allen, S.E.

ALLEN DESIGNS

Consulting Structural Engineers
V (949) 248-8588 • F(949) 209-2509

A Good Credit Score is 700 or Above. See yours in just 2 easy steps!