Structural Engineering: 2008-11-09

Saturday, November 15, 2008

Re: Flush Moment end plate connections

Rand,
You can download a free one from Alex's Corner. Just google that or
Structural Engineer's Association of South Carolina for a long list of
Excel spread sheets.
Gary

Rand W Holtham wrote:
> I was setting down to write a spreadsheet to do flush and extended multiple
> row moment end plate connections per AISC Design Guide #16. Is anyone aware
> of a commercially available spreadsheet that is available.
>
> TIA,
>
> Rand
>
>
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Friday, November 14, 2008

Re: Sg rods at purlins

Drew,
<rant on>
Sorry, but I have to cringe every time that I hear the term "sag rods". A
"sag rod" is strictly an alignment component. I know of very few times that
I have encountered a design where the "sag rod" was not also required as a
stability brace for axial or moment effects. This applies to both
manufactured and conventional construction.

The problem with referring to these as sag rods is that the field personnel
may not install them because they have taken measures to ensure the
supported member is aligned during construction so the sag rod was an
unnecessary waste of time - for the past 30 years. Please use the term
flange brace or stabilizer - especially on construction drawings. I think
that Newman uses an adequate term in his book - but I've forgotten it at the
moment.
<rant off>

Okay, I feel better.

If you do a quick check you will be able to determine a couple things about
your situation:
1) Does the Z purlin require a brace-point to achieve the original design
load capacity (probably uplift)? If so, the angle is a stability brace.
2) Is the roof cladding through-fastened vs. sliding clip standing seam?
AISI standard permits the use of a reduced Z section strength limit without
discrete bracing under certain conditions. Some stability bracing is still a
good idea on 24' span, anyway.

Purlin stabilizer bracing has been poorly done by many manufacturers over
the years. The most neglected consideration being accumulated forces in the
stabilizer line.

I would strongly recommend that, at the very least, you replace any such
angles that you remove. Better yet, check the design requirements with the
standards. Since you mention upgraded gravity loads and added purlins you
may need to include improved stabilizers and anchorage.

Regards
Paul

> From: Drew Morris <dmorris@bbfm.com>

> I have a question on sag rods. The project that I am working on is a
> pre-manufactured building (unknown manufacturer) with a roof slope of
> 1:12. The 8" deep roof zee purlins span 24 feet and there is an
> L3/4x3/4x 12 gage angle at the midspan that intersects the purlins about
> 5" down from the top. Based on the photos, the angles are not
> continuous from purlin to purlin and seem to be offset vertically, i.e.
> come in different heights on either side of the purlins. We are
> upgrading the roof system for higher snow and seismic loads and need to
> infill with new matching purlins to get the spacing down. Do you have
> any idea whether these angles are sag rods? Since the roof panels are
> already inplace, our thinking was that the sag rods could be cut away
> since the new infill purlins could be installed and screwed to the roof
> panels.

Re: STRESS AND FORCE

On Nov 14, 2008, at 7:29 PM, Acharya, Suresh wrote:

> Back to the stress vs. force discussion, the strength of materials
> (?) book
> by Byars, Snyder and Plants in the failure theory section or
> similar chapter
> (which I read about a decade ago), discusses why forces are better
> than
> stresses to define factor of safety or failure in real world
> structures.
> Some of the reasons being the effort to correlate the triaxial
> stress state
> in a structural element to the material strengths that are measured in
> uniaxial tests; other modes of failure (such as instability/shape)
> being
> more critical; brittle or ductile classification of materials being
> subjective and that often depending on temperature and other
> environmental
> conditions, etc.
I think I'll stick to my guns.

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/members/chrisw/

Re: Water Bag Load Testing

Matthew:

I have unfortunately found it necessary to load test a number of
concrete structures and have used bulk sand, barrels of water, and
water pools. For your situation, the water pools would likely be the
most practical. Use plastic sheeting and plywood forms to temporarily
hold the water over one area. Then reuse the water and materials in
the next area. This method is relatively simple and straightforward,
and therefore, relatively inexpensive. However, all load tests are
fairly expensive because of the required instrumentation and
monitoring.

Good luck,

Stan R. Caldwell, P.E.
Richardson, Texas

Re: STRESS AND FORCE

Hi, Joe,

I had to look it up, sounded both delicious and entertaining, like this Mama Sake sushi place in Squaw Valley right under the slopes...

Anyway, you point is hard to argue with.

Happy Friday,

V. Steve Gordin, SE
Irvine CA

----- Original Message -----

From: Jnapd@aol.com

To: seaint@seaint.org

Sent: Friday, November 14, 2008 14:58

Subject: Re: STRESS AND FORCE

Steve

It may be time for brewski......

Joe Venuti
Johnson & Nielsen Associates
Palm Springs, CA

In a message dated 11/14/2008 12:35:34 P.M. Pacific Standard Time, sgordin@sgeconsulting.com writes:

Ouch.

----- Original Message -----

From: Christopher Wright

To: seaint@seaint.org

Sent: Friday, November 14, 2008 11:05

Subject: Re: STRESS AND FORCE

On Nov 14, 2008, at 12:46 PM, Acharya, Suresh wrote:

> Question arises which stress you want to use a indicator? Principal
> stresses, Von Mises stress, or stresses based on several other
> hypothesis?

Not to beat this topic to death, but that question was answered in
sophomore strength of materials--the chapter on failure theories. von
Mises or maximum shear for ductile materials, maximum principle
stress for materials like cast iron or for crack propagation. Every
criterion depending on plastic flow has to be related to yield stress.

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/members/chrisw/

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RE: STRESS AND FORCE

-----Original Message-----
From: Christopher Wright [mailto:chrisw@skypoint.com]
Sent: Friday, November 14, 2008 11:06 AM
To: seaint@seaint.org
Subject: Re: STRESS AND FORCE

On Nov 14, 2008, at 12:46 PM, Acharya, Suresh wrote:

> Question arises which stress you want to use a indicator? Principal
> stresses, Von Mises stress, or stresses based on several other
> hypothesis?

Not to beat this topic to death, but that question was answered in sophomore
strength of materials--the chapter on failure theories. von Mises or maximum
shear for ductile materials, maximum principle stress for materials like
cast iron or for crack propagation. Every criterion depending on plastic
flow has to be related to yield stress.

===============================
Thanks for reminder!

Back to the stress vs. force discussion, the strength of materials (?) book
by Byars, Snyder and Plants in the failure theory section or similar chapter
(which I read about a decade ago), discusses why forces are better than
stresses to define factor of safety or failure in real world structures.
Some of the reasons being the effort to correlate the triaxial stress state
in a structural element to the material strengths that are measured in
uniaxial tests; other modes of failure (such as instability/shape) being
more critical; brittle or ductile classification of materials being
subjective and that often depending on temperature and other environmental
conditions, etc.

-Suresh Acharya, S.E.
===============================

Glazing Blast Loads

For blast loads on glazing per UFC 4-010-01, what is the load that the connections and glass frames have to take?

In this Structure Mag article it says:

"Framing members and connections are designed for a service load equal to two times the resistance of the glazing"

http://www.structuremag.org/article.aspx?articleID=760

1. There is a huge difference in designing for 2 times the resistance of the glazing as compared to what ASTM F2248 says:

"This practice assumes the framing system supporting the blast resistant glazing shall attach mechanically to the structural framing system with fasteners that will resist forces generated by a uniform load acting on the blast resistant glazing that has a magnitude AT LEAST 2 TIMES THE MAGNITUDE OF THE 3-SECOND EQUIVALENT DESIGN LOAD AS DETERMINED HEREIN." ("HEREIN" lies loads that are based on standoff distances and amount of explosive, not on the resistance of the glazing system)

2. Also, the UFC says on page B-15:

"The actual design load is dictated by the glass type and thickness determined by ASTM E1300" ( I take this to mean the connections should equal at least 1.0 times the glazing resistance?)

and

"The connection design load will be determined in accordance with ASTM F 2248 based on the applicable explosive weight at the actual standoff distance at
which the window is sited, but not greater than the conventional construction standoff distance."

http://www.wbdg.org/ccb/DOD/UFC/ufc_4_010_01.pdf

3. ASTM E1300 has nothing about connection design that I can find.

So where is 2 times the resistance coming from?

W. Haynes

Re: Sg rods at purlins

There should be a tie rod at the ridge that connects the first purlin to one another on each side of the ridge, this rod cancels out the gravity loads. If it is not there, then the angles aren't taking the sag out anyway but could be helping to brace the purlins from LTB.

If there is a structural diaphragm in place, you might can take away the sag rods/angles if the diaphragm can take the gravity load parallel with the slope in addition to the other loads it will take. But I don't ever really like to recommend cutting any steel from a premanufactured metal building regardless. Since they are angles instead of rods, I am afraid they are also functioning to brace the purlins.

On Fri, Nov 14, 2008 at 3:24 PM, Padmanabhan Rajendran <prajendran@ymail.com> wrote:

Although not that common anymore, sag rags were used in purlins too. Some of the old designs had channel sections for the purlins. On a sloping roof. the sag rods would transfer the component of the roof gravity load, in the direction parallel to the slope, to the ridge beam. With a shorter spacing of the sag rods between the purlins, the purlin will see relatively a smaller magnitude of any lateral load.

Without additional information, it is difficult to comment on Morris's project. It depends on how the angle members are connected near the ridge of the roof. If these members on either slopes are not connected together at the ridge, they may not function as either sag rods or as purlin braces.

Rajendran

--- On Fri, 11/14/08, Harold Sprague <spraguehope@hotmail.com> wrote:

From: Harold Sprague <spraguehope@hotmail.com>
Subject: RE: Sg rods at purlins
To: seaint@seaint.org
Date: Friday, November 14, 2008, 1:56 AM

Sag rods are used for girts as opposed to purlins. I would guess from you discription that they are secondary bracing elements for wind uplift when the bottom of the zee purlins go into compression. Unfortunately, these are generally deterimined directly from testing as opposed to deriving formulas based on testing. That is how the PEMB industry justifies the use of standing seam clips to provide bracing for the compression flanges in the zee purlins for gravity loads.

Regards, Harold Sprague

> Date: Thu, 13 Nov 2008 15:01:20 -0900
> From: dmorris@bbfm.com
> To: seaint@seaint.org
> Subject: Sg rods at purlins
>
> I have a question on sag rods. The project that I am working on is a
> pre-manufactured building (unknown manufacturer) with a roof slope of
> 1:12. The 8" deep roof zee purlins span 24 feet and there is an
> L3/4x3/4x 12 gage angle at the midspan that intersects the purlins about
> 5" down from the top. Based on the photos, the angles are not
> continuous from purlin to purlin and seem to be offset vertically, i.e.
> come in different heights on either side of the purlins. We are
> upgrading the roof system for higher snow and seismic loads and need to
> infill with new matching purlins to get the spacing down. Do you have
> any idea whether these angles are sag rods? Since the roof panels are
> already inplace, our thinking was that the sag rods could be cut away
> since the new infill purlins could be installed and screwed to the roof
> panels.
>
> ******* ****** ******* ******** ******* ******* ******* ***
> * 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
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Re: STRESS AND FORCE

Steve

It may be time for brewski......

Joe Venuti
Johnson & Nielsen Associates
Palm Springs, CA

In a message dated 11/14/2008 12:35:34 P.M. Pacific Standard Time, sgordin@sgeconsulting.com writes:

Ouch.

----- Original Message -----

From: Christopher Wright

To: seaint@seaint.org

Sent: Friday, November 14, 2008 11:05

Subject: Re: STRESS AND FORCE

On Nov 14, 2008, at 12:46 PM, Acharya, Suresh wrote:

> Question arises which stress you want to use a indicator? Principal
> stresses, Von Mises stress, or stresses based on several other
> hypothesis?

Not to beat this topic to death, but that question was answered in
sophomore strength of materials--the chapter on failure theories. von
Mises or maximum shear for ductile materials, maximum principle
stress for materials like cast iron or for crack propagation. Every
criterion depending on plastic flow has to be related to yield stress.

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/members/chrisw/

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RE: Flush Moment end plate connections

Daniel Li, PE has been writing spreadsheet shareware for years. (see http://www.engineering-international.com/)

-----Original Message-----
From: Gerard Madden, SE [mailto:gmse4603@gmail.com]
Sent: Friday, November 14, 2008 3:47 PM
To: seaint@seaint.org
Subject: Re: Flush Moment end plate connections

I wrote one for RBS's that took about 40 hours of my time, extended end plate is going to be likely more work. See the new AISC provisions for prequalification before you begin.

Don't know of any commercial software, but there is a guy who sells spreadsheets in So-Cal, Li I think is the last name, he may have one.

-gm

On Fri, Nov 14, 2008 at 11:59 AM, Rand W Holtham <RHoltham@cbi.com> wrote:

I was setting down to write a spreadsheet to do flush and extended multiple
row moment end plate connections per AISC Design Guide #16. Is anyone aware
of a commercially available spreadsheet that is available.

TIA,

Rand

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Wood SW compression check.

I am designing a 3-story wood-framed building and checking the uplift and compression at shear wall ends. I am using CBC 2007/IBC 2006 Alternate (ASD) Load Combinations with -2/3DL+ (1.3)W for uplift and DL+L+(1.3)W for compression. My colleague told me that I don't have to use live load to check compression and this is an industrial standard. He is more experience than I am and I respect his opinion, but I really wonder if this is an industrial standard which I have never heard of. Any comments or suggestions?

Thanks.

Michael

Re: Flush Moment end plate connections

I wrote one for RBS's that took about 40 hours of my time, extended end plate is going to be likely more work. See the new AISC provisions for prequalification before you begin.

Don't know of any commercial software, but there is a guy who sells spreadsheets in So-Cal, Li I think is the last name, he may have one.

-gm

On Fri, Nov 14, 2008 at 11:59 AM, Rand W Holtham <RHoltham@cbi.com> wrote:

I was setting down to write a spreadsheet to do flush and extended multiple
row moment end plate connections per AISC Design Guide #16. Is anyone aware
of a commercially available spreadsheet that is available.

TIA,

Rand

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Re: STRESS AND FORCE

Ouch.

----- Original Message -----

From: Christopher Wright

To: seaint@seaint.org

Sent: Friday, November 14, 2008 11:05

Subject: Re: STRESS AND FORCE

On Nov 14, 2008, at 12:46 PM, Acharya, Suresh wrote:

> Question arises which stress you want to use a indicator? Principal
> stresses, Von Mises stress, or stresses based on several other
> hypothesis?

Not to beat this topic to death, but that question was answered in
sophomore strength of materials--the chapter on failure theories. von
Mises or maximum shear for ductile materials, maximum principle
stress for materials like cast iron or for crack propagation. Every
criterion depending on plastic flow has to be related to yield stress.

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/members/chrisw/

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*   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
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RE: Sg rods at purlins

Although not that common anymore, sag rags were used in purlins too. Some of the old designs had channel sections for the purlins. On a sloping roof. the sag rods would transfer the component of the roof gravity load, in the direction parallel to the slope, to the ridge beam. With a shorter spacing of the sag rods between the purlins, the purlin will see relatively a smaller magnitude of any lateral load.

Without additional information, it is difficult to comment on Morris's project. It depends on how the angle members are connected near the ridge of the roof. If these members on either slopes are not connected together at the ridge, they may not function as either sag rods or as purlin braces.

Rajendran

--- On Fri, 11/14/08, Harold Sprague <spraguehope@hotmail.com> wrote:

From: Harold Sprague <spraguehope@hotmail.com>
Subject: RE: Sg rods at purlins
To: seaint@seaint.org
Date: Friday, November 14, 2008, 1:56 AM

Sag rods are used for girts as opposed to purlins. I would guess from you discription that they are secondary bracing elements for wind uplift when the bottom of the zee purlins go into compression. Unfortunately, these are generally deterimined directly from testing as opposed to deriving formulas based on testing. That is how the PEMB industry justifies the use of standing seam clips to provide bracing for the compression flanges in the zee purlins for gravity loads.

Regards, Harold Sprague

> Date: Thu, 13 Nov 2008 15:01:20 -0900
> From: dmorris@bbfm.com
> To: seaint@seaint.org
> Subject: Sg rods at purlins
>
> I have a question on sag rods. The project that I am working on is a
> pre-manufactured building (unknown manufacturer) with a roof slope of
> 1:12. The 8" deep roof zee purlins span 24 feet and there is an
> L3/4x3/4x 12 gage angle at the midspan that intersects the purlins about
> 5" down from the top. Based on the photos, the angles are not
> continuous from purlin to purlin and seem to be offset vertically, i.e.
> come in different heights on either side of the purlins. We are
> upgrading the roof system for higher snow and seismic loads and need to
> infill with new matching purlins to get the spacing down. Do you have
> any idea whether these angles are sag rods? Since the roof panels are
> already inplace, our thinking was that the sag rods could be cut away
> since the new infill purlins could be installed and screwed to the roof
> panels.
>
> ******* ****** ******* ******** ******* ******* ******* ***
> * 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
> ******* ****** ****** ****** ******* ****** ****** ********

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Flush Moment end plate connections

I was setting down to write a spreadsheet to do flush and extended multiple
row moment end plate connections per AISC Design Guide #16. Is anyone aware
of a commercially available spreadsheet that is available.

TIA,

Rand

Fwd: Compression check

I am designing a 3-story wood-frame building and checking the uplift and compression at shearwall ends at the bottom level. Per CBC 2007 I am applying the Alternate (ASD) load combination of -2/3DL+(1.3)W for uplift and DL+L+(1.3)W for compression. My well respected colleague told me that I don't have to use live load to check compression and this is an industrial standard. He is more experience than I am and I respect his opinion, but I really wonder if this is an industrial standard.! Any comment or suggestion.

Thanks.

Michael

Re: STRESS AND FORCE

On Nov 14, 2008, at 12:46 PM, Acharya, Suresh wrote:

> Question arises which stress you want to use a indicator? Principal
> stresses, Von Mises stress, or stresses based on several other
> hypothesis?

Not to beat this topic to death, but that question was answered in
sophomore strength of materials--the chapter on failure theories. von
Mises or maximum shear for ductile materials, maximum principle
stress for materials like cast iron or for crack propagation. Every
criterion depending on plastic flow has to be related to yield stress.

Re: STRESS AND FORCE

On Nov 14, 2008, at 11:40 AM, Bill Allen wrote:
> Why are you being such a trouble maker? You must be bored.
Careful, there. I've kept all my old whiny e-mails on LRFD vs. ASD
and I'm not afraid to use them. ;->

The reason that stress trumps load is that yield stress is required
to determine the load where plastification begins (in ductile
materials anyway). If you don't know the load for the onset of
plasticity you can't make use of the plastic reserve to determine the
limit load. You also won't know much about suitability for service in
situations where the structure remains elastic.

RE: STRESS AND FORCE

From: SGE Structural [mailto:sgordin@sgeconsulting.com]
Sent: Thursday, November 13, 2008 9:31 AM
To: seaint@seaint.org
Subject: STRESS AND FORCE

Struggling through the 2007 AASHTO BDS, I fail to understand one very basic thing. There was a good thing invented once, called stress, why the new codes use forces instead?

The use of forces - as those of resistance or loading - is so less informative, and does not give the same feel for the performance of material/component.

===============

Stresses are actually not a good indicator of failure. Factor of safety based on stresses are over-simplification. Question arises which stress you want to use a indicator? Principal stresses, Von Mises stress, or stresses based on several other hypothesis? Or, should we carry the whole state of stress in a form of stress vector and compare with the unknown "allowable stresses"?

-Suresh Acharya, S.E.

===============

Of course, all new equations allow conversion into stress, but why the change?

V. Steve Gordin, SE
Irvine CA

RE: Water Bag Load Testing

Thanks for the lead.

D. Matthew Stuart, P.E., S.E., F.ASCE, SECB

Senior Project Manager

Structural Department

Associate

CMX

200 Route 9

Manalapan, NJ 07726

732-577-9000 (Ext. 1285)

908-309-8657 (Cell)

732-298-9441 (Fax)

mstuart@CMXEngineering.com

From: Ken Loush [mailto:kloush@eews.com]
Sent: Friday, November 14, 2008 1:34 PM
To: seaint@seaint.org
Subject: RE: Water Bag Load Testing

Architectural Testing Inc. from York, PA may be able to help. I'm not certain if they have done this specific type of test but they are very experienced and always looking for a challenge. Call Joe Wise at 717-764-7700.

Good Luck.....

Kenneth Loush, P.E. (LU '76)

Eastern Exterior Wall Systems, Inc.

3400 High Point Blvd.

Bethlehem, PA 18017

P: 610-868-5522 x313

F: 484-893-2471

C: 484-357-0059

From: Stuart, Matthew [mailto:mStuart@cmxengineering.com]
Sent: Friday, November 14, 2008 9:36 AM
To: seaint@seaint.org
Subject: Water Bag Load Testing

I am looking for any contacts you may have for contractors in the US that are capable of using water bags for load testing of an existing structure.

Thanks

D. Matthew Stuart, P.E., S.E., F.ASCE, SECB

Senior Project Manager

Structural Department

Associate

CMX

200 Route 9

Manalapan, NJ 07726

732-577-9000 (Ext. 1285)

908-309-8657 (Cell)

732-298-9441 (Fax)

mstuart@CMXEngineering.com

Adjunct Professor

P.C. Rossin College of Engineering and Applied Science

Department of Civil and Environmental Engineering

Masters of Structural Engineering Program

Room 405

Fritz Lab

Lehigh University

13 East Packer Avenue

Bethlehem, PA 18015

dms308@lehigh.edu

RE: Water Bag Load Testing

Good Luck.....

Kenneth Loush, P.E. (LU '76)

Eastern Exterior Wall Systems, Inc.

3400 High Point Blvd.

Bethlehem, PA 18017

P: 610-868-5522 x313

F: 484-893-2471

C: 484-357-0059

From: Stuart, Matthew [mailto:mStuart@cmxengineering.com]
Sent: Friday, November 14, 2008 9:36 AM
To: seaint@seaint.org
Subject: Water Bag Load Testing

I am looking for any contacts you may have for contractors in the US that are capable of using water bags for load testing of an existing structure.

Thanks

D. Matthew Stuart, P.E., S.E., F.ASCE, SECB

Senior Project Manager

Structural Department

Associate

CMX

200 Route 9

Manalapan, NJ 07726

732-577-9000 (Ext. 1285)

908-309-8657 (Cell)

732-298-9441 (Fax)

mstuart@CMXEngineering.com

Adjunct Professor

P.C. Rossin College of Engineering and Applied Science

Department of Civil and Environmental Engineering

Masters of Structural Engineering Program

Room 405

Fritz Lab

Lehigh University

13 East Packer Avenue

Bethlehem, PA 18015

dms308@lehigh.edu

RE: STRESS AND FORCE

O.K. Steve, I'll take the bait.

While stress level analysis is a good indicator of service, it is not a good indicator of failure. I mean, really, do you believe Mc/I to failure?

That being said, as a design engineer it only started to make sense using LRFD when I was no longer permitted to use a 1/3 increase in allowable stresses / allowable loads.

I think I was one of the last engineers to stop using ASD for concrete. My rationalization (a high falootin' term for excuse) was that all the concrete I design (mostly residential foundations) remain in the elastic range anyway and crack control was paramount. But, hey, what do I know? I just wonder why all those two way slabs designed in the 80s and 90s have such a high rate of service problems due to deflection. Somebody tell me because I have no idea!

Why are you being such a trouble maker? You must be bored.

:o)

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

ALLEN DESIGNS

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

-----Original Message-----
From: SGE Structural [mailto:sgordin@sgeconsulting.com]
Sent: Thursday, November 13, 2008 9:31 AM
To: seaint@seaint.org
Subject: STRESS AND FORCE

Struggling through the 2007 AASHTO BDS, I fail to understand one very basic thing. There was a good thing invented once, called stress, why the new codes use forces instead?

The use of forces - as those of resistance or loading - is so less informative, and does not give the same feel for the performance of material/component.

Of course, all new equations allow conversion into stress, but why the change?

V. Steve Gordin, SE
Irvine CA

RE: Sg rods at purlins

Hi,

From what you have described those angles seem to be providing lateral support for the purlin's week axis. Depending on the purlin, the angle between its main axis and Y-axis and the slope of the roof a tension-only member (rod) or a tension-compression member would be used for this purpose. If the roof plate and its connection to purlins can provide a sufficient support then these will not be required. This applies to all purlins not only the new ones.

HTH,
Reza Dashti P.Eng
Vancover, BC

> Date: Thu, 13 Nov 2008 15:01:20 -0900
> From: dmorris@bbfm.com
> To: seaint@seaint.org
> Subject: Sg rods at purlins
>
> I have a question on sag rods. The project that I am working on is a
> pre-manufactured building (unknown manufacturer) with a roof slope of
> 1:12. The 8" deep roof zee purlins span 24 feet and there is an
> L3/4x3/4x 12 gage angle at the midspan that intersects the purlins about
> 5" down from the top. Based on the photos, the angles are not
> continuous from purlin to purlin and seem to be offset vertically, i.e.
> come in different heights on either side of the purlins. We are
> upgrading the roof system for higher snow and seismic loads and need to
> infill with new matching purlins to get the spacing down. Do you have
> any idea whether these angles are sag rods? Since the roof panels are
> already inplace, our thinking was that the sag rods could be cut away
> since the new infill purlins could be installed and screwed to the roof
> panels.
>
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RE: Water Bag Load Testing

Whoa, now that is a test specimen! Good luck.

Tom

From: Stuart, Matthew [mailto:mStuart@cmxengineering.com]
Sent: Friday, November 14, 2008 08:39
To: seaint@seaint.org
Subject: RE: Water Bag Load Testing

100 to 200 PSF, but the area involved is huge – 200,000 SF – 60x60 chunks at a time.

D. Matthew Stuart, P.E., S.E., F.ASCE, SECB

Senior Project Manager

Structural Department

Associate

CMX

200 Route 9

Manalapan, NJ 07726

732-577-9000 (Ext. 1285)

908-309-8657 (Cell)

732-298-9441 (Fax)

mstuart@CMXEngineering.com

From: Tom Skaggs [mailto:tom.skaggs@apawood.org]
Sent: Friday, November 14, 2008 10:24 AM
To: seaint@seaint.org
Subject: RE: Water Bag Load Testing

Sorry, I can’t provide you any help, but I’m curious what magnitude of the pressures you are trying to apply?

Tom

Thomas D. Skaggs, Ph.D., P.E.

Manager, Product Evaluation

APA

7011 S. 19th Street

Tacoma, WA 98466

253-620-7479 (office)

253-620-7235 (fax)

tom.skaggs@apawood.org

www.apawood.org

From: Stuart, Matthew [mailto:mStuart@cmxengineering.com]
Sent: Friday, November 14, 2008 06:36
To: seaint@seaint.org
Subject: Water Bag Load Testing

I am looking for any contacts you may have for contractors in the US that are capable of using water bags for load testing of an existing structure.

Thanks

D. Matthew Stuart, P.E., S.E., F.ASCE, SECB

Senior Project Manager

Structural Department

Associate

CMX

200 Route 9

Manalapan, NJ 07726

732-577-9000 (Ext. 1285)

908-309-8657 (Cell)

732-298-9441 (Fax)

mstuart@CMXEngineering.com

Adjunct Professor

P.C. Rossin College of Engineering and Applied Science

Department of Civil and Environmental Engineering

Masters of Structural Engineering Program

Room 405

Fritz Lab

Lehigh University

13 East Packer Avenue

Bethlehem, PA 18015

dms308@lehigh.edu

RE: Water Bag Load Testing

Water weights are sometimes used as test weights to certify cranes. Maybe a crane certifier could give you a lead.

Regards,

Al Greene, PE, SECB
Office 510-242-9010
Fax 510-242-9448
Cell 510-507-5080
RIC145-2124A
1450 Marina Way South
Richmond, CA 94804

From: Stuart, Matthew [mailto:mStuart@cmxengineering.com]
Sent: Friday, November 14, 2008 6:36 AM
To: seaint@seaint.org
Subject: Water Bag Load Testing

I am looking for any contacts you may have for contractors in the US that are capable of using water bags for load testing of an existing structure.

Thanks

D. Matthew Stuart, P.E., S.E., F.ASCE, SECB

Senior Project Manager

Structural Department

Associate

CMX

200 Route 9

Manalapan, NJ 07726

732-577-9000 (Ext. 1285)

908-309-8657 (Cell)

732-298-9441 (Fax)

mstuart@CMXEngineering.com

Adjunct Professor

P.C. Rossin College of Engineering and Applied Science

Department of Civil and Environmental Engineering

Masters of Structural Engineering Program

Room 405

Fritz Lab

Lehigh University

13 East Packer Avenue

Bethlehem, PA 18015

dms308@lehigh.edu

RE: Water Bag Load Testing

100 to 200 PSF, but the area involved is huge – 200,000 SF – 60x60 chunks at a time.

D. Matthew Stuart, P.E., S.E., F.ASCE, SECB

Senior Project Manager

Structural Department

Associate

CMX

200 Route 9

Manalapan, NJ 07726

732-577-9000 (Ext. 1285)

908-309-8657 (Cell)

732-298-9441 (Fax)

mstuart@CMXEngineering.com

From: Tom Skaggs [mailto:tom.skaggs@apawood.org]
Sent: Friday, November 14, 2008 10:24 AM
To: seaint@seaint.org
Subject: RE: Water Bag Load Testing

Sorry, I can’t provide you any help, but I’m curious what magnitude of the pressures you are trying to apply?

Tom

Thomas D. Skaggs, Ph.D., P.E.

Manager, Product Evaluation

APA

7011 S. 19th Street

Tacoma, WA 98466

253-620-7479 (office)

253-620-7235 (fax)

tom.skaggs@apawood.org

www.apawood.org

From: Stuart, Matthew [mailto:mStuart@cmxengineering.com]
Sent: Friday, November 14, 2008 06:36
To: seaint@seaint.org
Subject: Water Bag Load Testing

I am looking for any contacts you may have for contractors in the US that are capable of using water bags for load testing of an existing structure.

Thanks

D. Matthew Stuart, P.E., S.E., F.ASCE, SECB

Senior Project Manager

Structural Department

Associate

CMX

200 Route 9

Manalapan, NJ 07726

732-577-9000 (Ext. 1285)

908-309-8657 (Cell)

732-298-9441 (Fax)

mstuart@CMXEngineering.com

Adjunct Professor

P.C. Rossin College of Engineering and Applied Science

Department of Civil and Environmental Engineering

Masters of Structural Engineering Program

Room 405

Fritz Lab

Lehigh University

13 East Packer Avenue

Bethlehem, PA 18015

dms308@lehigh.edu