Structural Engineering: 2008-10-12

Saturday, October 18, 2008

Southern Calif residential Engineers

Just wondering how the downturn in the economy has effected your business. I
work at a small eng firm in Orange county and we have almost completely run
out of business. Bids go out but no answer back, and this is to clients that
we usually do business with.

I should mention that we specialize in residential.

Just curious.

Erik Gibbs

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Friday, October 17, 2008

RE: Seismic Factors for Soil Nail Walls

Yes, that is huge on the fault line ! 1/2 * 1.25 is gigantic, or perhaps it is better to use the 1 sec Response, so this could be 1/2 * 0.93 = 0.465, still huge.

http://www.facweb.iitkgp.ernet.in/~nirjhar/GT103_09.pdf

I found the link above which kind of says the same thing.

How about a temporary wall?

Thanks for the feedback.

Refugio

--- On Fri, 10/17/08, Mark D. Baker <shake4bake@verizon.net> wrote:

From: Mark D. Baker <shake4bake@verizon.net>
Subject: RE: Seismic Factors for Soil Nail Walls
To: seaint@seaint.org
Date: Friday, October 17, 2008, 3:40 PM

Refugio,

On a recent project, the geotech and I discussed his basis for the kh value he was providing. In a nutshell he said after all their research on the methods for determining kh, they concluded that they would always specify ½ of the PGA and feel comfortable with that recommendation.

Incorporating seismic into retaining structures certainly impacts the design of structure, ½ or more of PGA is a substantial force to account for.

Mark D. Baker
Baker Engineering

From: refugio rochin [mailto:refugio311@yahoo.com]
Sent: Friday, October 17, 2008 9:34 AM
To: seaint@seaint.org
Subject: Seismic Factors for Soil Nail Walls

I have a question regarding Soil Nail Walls in a high seismic region. We are trying to identify the seismic factors for such a wall. A geotechnical circular No. 7

http://isddc.dot.gov/OLPFiles/FHWA/010946.pdf

pdf

as well as the FHWA Soil Nail Manual, utilize the equation Am = (1.45 - A)A where A is the peak ground acceleration at 10% exceedance in 50 years. This equation however has a maximum at 0.725, and our PGA is 1.25 to 1.1 (located on the San Andreas Fault , site specific spectra and USGS spectra, respectively). I am not sure if this equation truly applies in this condition.

The target is to define the kh, which is a pseudo-static coefficient input into the Soil Nail programs.

Refugio

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RE: Seismic Factors for Soil Nail Walls

Refugio,

On a recent project, the geotech and I discussed his basis for the kh value he was providing. In a nutshell he said after all their research on the methods for determining kh, they concluded that they would always specify ½ of the PGA and feel comfortable with that recommendation.

Incorporating seismic into retaining structures certainly impacts the design of structure, ½ or more of PGA is a substantial force to account for.

Mark D. Baker

Baker Engineering

From: refugio rochin [mailto:refugio311@yahoo.com]
Sent: Friday, October 17, 2008 9:34 AM
To: seaint@seaint.org
Subject: Seismic Factors for Soil Nail Walls

I have a question regarding Soil Nail Walls in a high seismic region. We are trying to identify the seismic factors for such a wall. A geotechnical circular No. 7

http://isddc.dot.gov/OLPFiles/FHWA/010946.pdf

pdf

as well as the FHWA Soil Nail Manual, utilize the equation Am = (1.45 - A)A where A is the peak ground acceleration at 10% exceedance in 50 years. This equation however has a maximum at 0.725, and our PGA is 1.25 to 1.1 (located on the San Andreas Fault, site specific spectra and USGS spectra, respectively). I am not sure if this equation truly applies in this condition.

The target is to define the kh, which is a pseudo-static coefficient input into the Soil Nail programs.

Refugio

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Re: Seismic Factors for Soil Nail Walls

Refugio,

I am not familiar with Soil Nail Walls, but if this is considered an Earth Retaining Structure then ASCE 7-05 Sections 15.6.1 and 11.8.3 would require that the lateral earth pressures be part of the Geotechnical Investigation Report.

Thomas Hunt

refugio rochin <refugio311@yahoo.com>
10/17/2008 09:34 AM
Please respond to seaint

To	seaint@seaint.org
cc
Subject	Seismic Factors for Soil Nail Walls

I have a question regarding Soil Nail Walls in a high seismic region. We are trying to identify the seismic factors for such a wall. A geotechnical circular No. 7
http://isddc.dot.gov/OLPFiles/FHWA/010946.pdf
pdf

as well as the FHWA Soil Nail Manual, utilize the equation Am = (1.45 - A)A where A is the peak ground acceleration at 10% exceedance in 50 years. This equation however has a maximum at 0.725, and our PGA is 1.25 to 1.1 (located on the San Andreas Fault, site specific spectra and USGS spectra, respectively). I am not sure if this equation truly applies in this condition.

The target is to define the kh, which is a pseudo-static coefficient input into the Soil Nail programs.

Refugio

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Seismic Factors for Soil Nail Walls

I have a question regarding Soil Nail Walls in a high seismic region. We are trying to identify the seismic factors for such a wall. A geotechnical circular No. 7

http://isddc.dot.gov/OLPFiles/FHWA/010946.pdf

pdf

The target is to define the kh, which is a pseudo-static coefficient input into the Soil Nail programs.

Refugio

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Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around
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Thursday, October 16, 2008

Re: OSHPD SCBF's using HSS Braces

Thanks Dr. Astaneh and Donny. I appreciate the info.

I remember reading, and it's probably in the AISC somewhere, the if the slenderness limits were exceeded, you could then fill the HSS's with concrete. This OSHPD requirement seems to apply to any HSS, slender or not, except rounds. I haven't used pipes for a SCBF before...

I'm pretty much a BRBF guy now anyway on my designs rather than SCBF's, but I'm in the early stages of a OSHPD peer review and need to make sure I let the other engineers know what to look out for.

I appreciate all the input from eveyone !

-gm

On Thu, Oct 16, 2008 at 10:43 AM, Donny Harris <dharris@kpff-la.com> wrote:

Gerald-

I am fairly certain the OSHPD restriction applies to square sections as
well though I do agree that in the AISC text a rectangle categorization
doesn't seem to always include squares, contrary to what I too was
taught in elementary school. I believe the cited testing which
indicated local stability problems with these sections actually used
square sections in the testing. (Uriz and Mahin was the testing cited
per the final statement of reasons for amendments to the CBC by OSHPD,
10/14/06)

If you are going to specify a round section I recommend you research
some of the additional recent testing and research. As I understand it
the round HSS braces with high compactness ratios close to but still
within the code limit may be subject to the same local stability issues.

Maybe the future codes will just revise the b/t ratios for HSS sections
of all shapes?

FYI; the City of Long Beach also has a similar restriction on
rectangular HSS in SCBFs. If anyone know of other cities or
jurisdictions that have adopted this I would be interested to know.

Donny Harris, SE

From: Gerard Madden, SE [mailto:gmse4603@gmail.com]
Sent: Wednesday, October 15, 2008 3:26 PM
To: seaint@seaint.org
Subject: OSHPD SCBF's using HSS Braces

Section 2205A.4.1.5.1 of the CBC modifies AISC 341 for SCBF's using

RECTANG= ULAR HSS sections. The section requires them to be filled solid

with cement= grout. This is for OSHPD only projects.

Question: Do the really mean Rectangular and Square HSS sections or only

Re= ctangular as stated?

thanks,
-gm

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Re: OSHPD SCBF's using HSS Braces

Gerald-

I am fairly certain the OSHPD restriction applies to square sections as
well though I do agree that in the AISC text a rectangle categorization
doesn't seem to always include squares, contrary to what I too was
taught in elementary school. I believe the cited testing which
indicated local stability problems with these sections actually used
square sections in the testing. (Uriz and Mahin was the testing cited
per the final statement of reasons for amendments to the CBC by OSHPD,
10/14/06)

If you are going to specify a round section I recommend you research
some of the additional recent testing and research. As I understand it
the round HSS braces with high compactness ratios close to but still
within the code limit may be subject to the same local stability issues.

Maybe the future codes will just revise the b/t ratios for HSS sections
of all shapes?

FYI; the City of Long Beach also has a similar restriction on
rectangular HSS in SCBFs. If anyone know of other cities or
jurisdictions that have adopted this I would be interested to know.

Donny Harris, SE

From: Gerard Madden, SE [mailto:gmse4603@gmail.com]
Sent: Wednesday, October 15, 2008 3:26 PM
To: seaint@seaint.org
Subject: OSHPD SCBF's using HSS Braces

Section 2205A.4.1.5.1 of the CBC modifies AISC 341 for SCBF's using
RECTANG= ULAR HSS sections. The section requires them to be filled solid
with cement= grout. This is for OSHPD only projects.

Question: Do the really mean Rectangular and Square HSS sections or only
Re= ctangular as stated?

thanks,
-gm

OSHPD SCBF's using HSS Braces

Dear Gerard:

I feel that the provisions of Section 2205A.4.1.5.1 of the CBC
on SCBF should be applied to the square HSS as well as rectangular sections. The reason is as Professor Goel's tests in Michigan have shown, when HSS sections are filled with concrete, their cyclic performance improves significantly, especially with regard to delaying the fracture of the locally buckled areas of the HSS at the location of the plastic hinges.

In rectangular HSS braces, usually the long side of the rectangle is vertical and since the brace buckles out -of-plane, it is this long side that is subjected to compression and local buckling. If you have a square shape, still the vertical side will be locally buckled but in square shape, the horizontal side is also as long as the vertical side and cannot provide as much restraint to the vertical side to help delay its local buckling. So, it seems to me that if we are worried about pre-mature cyclic local buckling of the rectangular HSS sections as SCBF members, we should be more concerned about square sections (given the same b/t ratio for both)

Another issue is that when we use square HSS instead of rectangular sections, for the same area, the square HSS, will have larger compressive capacity , since out-of-plane KL/r will be smaller for the square section compared to rectangular section with the same area. But, the square section will have smaller tension capacity than the rectangular section since the shear lag factor "U" for square HSS will be greater. Of course from architectural point of view, rectangular section are preferred since they have smaller width and easy to hide inside the walls.

Finally, I wanted to mention an item regarding filling the HSS braces with grout. Last year I had an e-mail from a structural engineer looking for information about performance of the concrete-filled HSS braces where the sides of the HSS section have "bulged-out" and in a way turned the 4-sided section into an 8-sided section. Apparently this happened because of the hydro-static pressure of the liquid grout placed inside the HSS. I think the final decision in this case was to replace the deformed braces. So, in specifying the grout fill-in, may be it is prudent to specify that the grout should be placed in sections ( may be two sections) especially if the story is high and the b/t ratio of the HSS is also relatively high. A simple hydro-static analysis can also be done to check this failure mode.

Best wishes.
"Hassan"

Abolhassan Astaneh-Asl, Ph.D., P.E.
Professor and Consultant on Structural Engineering
www.astaneh.net
www.ce.berkeley.edu/~astaneh

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

From: Gerard Madden, SE [mailto:gmse4603@gmail.com]
Sent: Wednesday, October 15, 2008 3:26 PM
To: seaint@seaint.org
Subject: OSHPD SCBF's using HSS Braces

Section 2205A.4.1.5.1 of the CBC modifies AISC 341 for SCBF's using
RECTANGULAR HSS sections. The section requires them to be filled solid with
cement grout. This is for OSHPD only projects.

Question: Do the really mean Rectangular and Square HSS sections or only
Rectangular as stated?

thanks,
-gm

Re: OSHPD SCBF's using HSS Braces

Matthew,

That's what I was thinking as well.

-gm

On Wed, Oct 15, 2008 at 4:03 PM, Matthew J Tobolski <mtobolski@tobolskiwatkins.com> wrote:

Going back to my elementary geometry class, a square is nothing more than a special case of a rectangle. Therefore, any code requirement for a rectangular HSS would also be a direct requirement for a square HSS. Extending this argument, any reference to a rhombus, parallelogram or trapezoidal HSS section would also be a reference for a square HSS J

--

Matthew Tobolski, P.E.

4832 Mt. La Palma Drive

San Diego, CA 92117

Cell:      858.822.8517

Fax:      858.764.5445

Email:   mailto:mtobolski@tobolskiwatkins.com

Visit us on the web at: www.tobolskiwatkins.com

From: Gerard Madden, SE [mailto:gmse4603@gmail.com]
Sent: Wednesday, October 15, 2008 3:26 PM
To: seaint@seaint.org
Subject: OSHPD SCBF's using HSS Braces

Section 2205A.4.1.5.1 of the CBC modifies AISC 341 for SCBF's using RECTANGULAR HSS sections. The section requires them to be filled solid with cement grout. This is for OSHPD only projects.

Question: Do the really mean Rectangular and Square HSS sections or only Rectangular as stated?

thanks,
-gm

Wednesday, October 15, 2008

RE: OSHPD SCBF's using HSS Braces

Gerard;

Last week I just had a plan check comment on a non-OSHPD project, on this very same item.

I think the language in that code section has problem.
You may want to email Chris Tokas at OSHPD and get a clarification.

I'd look at AISC 341-05 Commentary section C13.2.d "With-Thickness Limitation" which indicates that the problem with Rectangular HSS's relates to local buckling with large "Width-Thickness" ratios.

Based on AISC 13th , there are 3 types of HSS's; Rectangular, Square and Round.
When you look at Table 1-11 of AISC 13th edition, Pages 1-72, 1-90, 1-94, there is a distinct difference between the three.

Casey K. Hemmatyar, SE

____________________________________________________________________________________________________
From: Gerard Madden, SE [mailto:gmse4603@gmail.com]
Sent: Wednesday, October 15, 2008 3:26 PM
To: seaint@seaint.org
Subject: OSHPD SCBF's using HSS Braces

Section 2205A.4.1.5.1 of the CBC modifies AISC 341 for SCBF's using RECTANGULAR HSS sections. The section requires them to be filled solid with cement grout. This is for OSHPD only projects.

Question: Do the really mean Rectangular and Square HSS sections or only Rectangular as stated?

thanks,
-gm

RE: Full Pen Weld at Channel

You can do any kind of weld you want, but you are limited on what prequalified welds are available. You can qualify any weld, but that takes some time. I just try to specify something that can be done by most shops, inspected by any inspector, and gets me to happy hour ASAP.

Regards,
Harold Sprague

> Date: Tue, 14 Oct 2008 23:10:11 -0700
> From: m_k_gilligan@yahoo.com
> Subject: Re: RE: Full Pen Weld at Channel
> To: seaint@seaint.org
>
> While the partial pen weld may sidestep several issues I am not convinced that you cannot produce a full pen weld without weld access holes. I would appreciate reasons why this is not possible.
>
> While the weld may not be pre-qualified it is not clear why a weld without a weld access hole cannot be qualified.
>
> Weld access holes are needed to allow access of the electrode but if you can weld from outside you could sidestep this requirement. This might result in a larger weld volume on one side in order to get access but it appears doable.
>
> If you weld the web after the flanges are welded you have an opportunity to deal with defects in the root. This might not be elegant and may require a fair amount of grinding but it might be the answer in some situations where weld access holes are not visually acceptable.
>
> In some ways UT might be easier without weld access holes since you do not need to deal with the discontinuity due to the 90 degree connection and the use of weld tabs that are left in place.
>
> Of coarse the other option would be to use the weld access holes and fill it with bondo.. It intrigues me that this is not used more often for architectural steel. Any suggestions on how to specify bondo.
>
> Mark Gilligan
>
> ******* ****** ******* ******** ******* ******* ******* ***
> * 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:
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RE: OSHPD SCBF's using HSS Braces

Going back to my elementary geometry class, a square is nothing more than a special case of a rectangle. Therefore, any code requirement for a rectangular HSS would also be a direct requirement for a square HSS. Extending this argument, any reference to a rhombus, parallelogram or trapezoidal HSS section would also be a reference for a square HSS J

Matthew Tobolski, P.E.

4832 Mt. La Palma Drive

San Diego, CA 92117

Cell: 858.822.8517

Fax: 858.764.5445

Email: mailto:mtobolski@tobolskiwatkins.com

Visit us on the web at: www.tobolskiwatkins.com

From: Gerard Madden, SE [mailto:gmse4603@gmail.com]
Sent: Wednesday, October 15, 2008 3:26 PM
To: seaint@seaint.org
Subject: OSHPD SCBF's using HSS Braces

Section 2205A.4.1.5.1 of the CBC modifies AISC 341 for SCBF's using RECTANGULAR HSS sections. The section requires them to be filled solid with cement grout. This is for OSHPD only projects.

Question: Do the really mean Rectangular and Square HSS sections or only Rectangular as stated?

thanks,
-gm

RE: OSHPD SCBF's using HSS Braces

I'm pretty sure it's rectangular and square as opposed to round HSS sections. Those sections were the only ones which have a tendency to buckle locally or at least more so than the round sections.

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

ALLEN DESIGNS

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

-----Original Message-----
From: Gerard Madden, SE [mailto:gmse4603@gmail.com]
Sent: Wednesday, October 15, 2008 3:26 PM
To: seaint@seaint.org
Subject: OSHPD SCBF's using HSS Braces

OSHPD SCBF's using HSS Braces

Re: RE: Full Pen Weld at Channel

"putty and paint make a carpenter what he ain't"

On Wed, Oct 15, 2008 at 7:41 AM, Garner, Robert <rgarner@moffattnichol.com> wrote:

Mark,

Interesting that you should mention specifying Bondo. I've done some AESS and for a certain project, we specified "Automotive Quality" paint on the AESS. This required surface prep not unlike concrete, but instead of dry sacking the surface, it was given a skim coat of Bondo before sanding and painting. This was a real specialty project and it was painted - yes - Candy Apple Red! This was a real "red iron" job.

Bob G.

-----Original Message-----
From: Mark Gilligan [mailto:m_k_gilligan@yahoo.com]
Sent: Tuesday, October 14, 2008 11:10 PM
To: seaint@seaint.org
Subject: Re: RE: Full Pen Weld at Channel

While the partial pen weld may sidestep several issues I am not convinced that you cannot produce a full pen weld without weld access holes. I would appreciate reasons why this is not possible.

While the weld may not be pre-qualified it is not clear why a weld without a weld access hole cannot be qualified.

Weld access holes are needed to allow access of the electrode but if you can weld from outside you could sidestep this requirement. This might result in a larger weld volume on one side in order to get access but it appears doable.

If you weld the web after the flanges are welded you have an opportunity to deal with defects in the root. This might not be elegant and may require a fair amount of grinding but it might be the answer in some situations where weld access holes are not visually acceptable.

In some ways UT might be easier without weld access holes since you do not need to deal with the discontinuity due to the 90 degree connection and the use of weld tabs that are left in place.

Of coarse the other option would be to use the weld access holes and fill it with bondo.. It intrigues me that this is not used more often for architectural steel. Any suggestions on how to specify bondo.

Mark Gilligan

******* ****** ******* ******** ******* ******* ******* ***
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*
* This email was sent to you via Structural Engineers
* Association of Southern California (SEAOSC) server. To
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* http://www.seaint.org/sealist1.asp
*
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* This email was sent to you via Structural Engineers
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--
David Topete, SE

RE: RE: Full Pen Weld at Channel

Mark,

Interesting that you should mention specifying Bondo. I've done some AESS and for a certain project, we specified "Automotive Quality" paint on the AESS. This required surface prep not unlike concrete, but instead of dry sacking the surface, it was given a skim coat of Bondo before sanding and painting. This was a real specialty project and it was painted - yes - Candy Apple Red! This was a real "red iron" job.

Bob G.

-----Original Message-----
From: Mark Gilligan [mailto:m_k_gilligan@yahoo.com]
Sent: Tuesday, October 14, 2008 11:10 PM
To: seaint@seaint.org
Subject: Re: RE: Full Pen Weld at Channel

While the partial pen weld may sidestep several issues I am not convinced that you cannot produce a full pen weld without weld access holes. I would appreciate reasons why this is not possible.

While the weld may not be pre-qualified it is not clear why a weld without a weld access hole cannot be qualified.

Weld access holes are needed to allow access of the electrode but if you can weld from outside you could sidestep this requirement. This might result in a larger weld volume on one side in order to get access but it appears doable.

If you weld the web after the flanges are welded you have an opportunity to deal with defects in the root. This might not be elegant and may require a fair amount of grinding but it might be the answer in some situations where weld access holes are not visually acceptable.

In some ways UT might be easier without weld access holes since you do not need to deal with the discontinuity due to the 90 degree connection and the use of weld tabs that are left in place.

Of coarse the other option would be to use the weld access holes and fill it with bondo.. It intrigues me that this is not used more often for architectural steel. Any suggestions on how to specify bondo.

Mark Gilligan

Tuesday, October 14, 2008

Re: RE: Full Pen Weld at Channel

While the partial pen weld may sidestep several issues I am not convinced that you cannot produce a full pen weld without weld access holes. I would appreciate reasons why this is not possible.

While the weld may not be pre-qualified it is not clear why a weld without a weld access hole cannot be qualified.

In some ways UT might be easier without weld access holes since you do not need to deal with the discontinuity due to the 90 degree connection and the use of weld tabs that are left in place.

Mark Gilligan

Re: RE: Full Pen Weld at Channel

Harold

What I was indicating was that the web only was welded with a square butt weld both sides. Most channel webs used for stringers are 3/8" or less and the only concern is shear so this is not a problem. I have seen many engineers call out a prep on the web as well. The joint I describe is not prequalified. I use 60 degrees because there is no gap. I know also from experience that it is almost impossible to get a good backgouge with a pencil grinder. The shops I have worked for usually instruct the welders to disregard the backgouge rather than get a gouging rod, making the final product different than what is called out.

On another note, most of my work has been in Canada where the welding code is law, not voluntary as the AWS codes are. All welders must be tested and ticketed for each weld they perform so whatever it is the shop finally does with my weld symbol, it would not go unnoticed by the governing authorities.

I have never heard of a stair failing at this joint. If anyone has would they please tell us about it?

Regards,

Dave Lowen
jatech@telus.net
Alberta 780.470.5187
California 510.550.7514

On Oct 14, 2008, spraguehope@hotmail.com wrote:

Dave,
I had the advantage of working in a steel shop with a very good fabricator of stairs (old guy who knew what he was doing). He was very meticulous. What I did with my weld call out was mimic the weld he routinely provided. After I became an engineer, I then put his weld into a symbol with a prequalified PJP weld augmented by notes. I then bounced my weld call out to inspectors and welding engineers like Bob Shaw and then back to some good shops for their input.

As a former welder, welding inspector, and now a half fast structural engineer, the weld I call out is about the best I could come up with the help of people who really knew their stuff (welders, inspectors, code guys).

I don't mean to criticize, but I do not understand how you call the weld that you suggest is a square butt weld but then call out a single bevel? It is either a square butt or a bevel weld. Any square butt weld has a very small thickness limitation. The thickness will be 3/4" (MC 12x10.6; k=3/4") and a maximum allowed for any prequalified CJP square butt SMAW is only 1/4". A 60 degree single bevel will require a lot of weld deposit material, a lot of grinding or a bevel cut, and will probably limit the welder to a SAW process. I don't know of any 60 degree prep that you can use a SMAW, GMAW, or FCAW (which are the most common shop processes). Not that many shops can do a SAW by hand. Backgouging is another process that is difficult especially as you approach the fillet. Again, I do not intend to criticize. If it works for you that is fine. You may want to get some feedback from the inspectors for their interpretation.

You are correct in that the weld you indicate is not a CJP. It will be a PJP. CJPs often trigger difficult NDT. The NDT is especially difficult if radiographic or UT is required. Frankly, I do not know of an easy NDT for this particular kind of weld. That is another reason that I prefer to require visual inspection. The inspector will observe the set up and the process to assure that the engineer gets the effective weld indicated. Another challenge is that the flange thickness varies. That is why I indicate the E to be the material thickness minus 1/8".

I prefer not to show the angle, root opening, or process. I leave that up to the shop and only show the effective thickness that I know that the shop can provide. That makes it easy on the welders, the inspectors, and most of all ...me.

Regards,
Harold Sprague

From: jatech@telus.net [mailto:jatech@telus.net]
Sent: Monday, October 13, 2008 3:52 PM
To: seaint@seaint.org
Subject: Re: RE: Full Pen Weld at Channel

For the last 45 years I have called for a square butt weld on both sides of the web and a 60 degree single bevel with zero gap and zero root face along with a backgouge symbol for both flanges. I know it's not a CP weld so I don't call it out as one.

These stringers are also called "cranked" in some areas.

Dave Lowen
jatech@telus.net
Alberta 780.470.5187
California 510.550.7514

On Oct 13, 2008, spraguehope@hotmail.com wrote:

This is a common issue. This is also known as a broke back stair stringer. Be careful so that you get what you intend. If you truly need a full pen weld, then specify what you need. If you get a true full pen weld, you will then have run off tabs and you will have a weld access hole through the web. It will not be pretty.

Now the architect will hate that hole and point out that no other broke back stringer in existance will have a weld access hole, and he will be correct.

You as the engineer have a dillema. Swimming upstream in the world of convention or engineering something that will satisfy most everyone.

I have had this conversation with a lot of welding and fabricating gurus and resoved to the following:
Show a PJP weld symbol with E in the spot indicating the effective weld thickness. In the tail of the weld symbol indicate:

PJP E=MTL THICKNESS - 1/8"
WELD ACCESS HOLE NOT REQUIRED
NDT NOT REQUIRED
VISUAL INSPECTION REQUIRED

Show the same weld symbol for the web weld. Calculate if this is sufficient for the weld you need.

You can have it ground flush if required.

The above weld will have a prepared beveled surface. It will be close to a CJP, but not quite. It will look like all of the other welds out there on stair stringers, but you will have some idea of what you have. The vast majority of these welds existing in the field are just butt welds that are not prequalified and you have no idea of the thickness of the effective weld.

Go to any project where there is a broke back stringer and you will not find a weld access hole even if the weld was specified as a CJP. It makes you wonder what weld was provided. At least with the notes that I now use, I am getting a definable weld and it is inspected.

Regards,
Harold Sprague

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RE: Full Pen Weld at Channel

Dave,
I had the advantage of working in a steel shop with a very good fabricator of stairs (old guy who knew what he was doing). He was very meticulous. What I did with my weld call out was mimic the weld he routinely provided. After I became an engineer, I then put his weld into a symbol with a prequalified PJP weld augmented by notes. I then bounced my weld call out to inspectors and welding engineers like Bob Shaw and then back to some good shops for their input.

As a former welder, welding inspector, and now a half fast structural engineer, the weld I call out is about the best I could come up with the help of people who really knew their stuff (welders, inspectors, code guys).

I don't mean to criticize, but I do not understand how you call the weld that you suggest is a square butt weld but then call out a single bevel? It is either a square butt or a bevel weld. Any square butt weld has a very small thickness limitation. The thickness will be 3/4" (MC 12x10.6; k=3/4") and a maximum allowed for any prequalified CJP square butt SMAW is only 1/4". A 60 degree single bevel will require a lot of weld deposit material, a lot of grinding or a bevel cut, and will probably limit the welder to a SAW process. I don't know of any 60 degree prep that you can use a SMAW, GMAW, or FCAW (which are the most common shop processes). Not that many shops can do a SAW by hand. Backgouging is another process that is difficult especially as you approach the fillet. Again, I do not intend to criticize. If it works for you that is fine. You may want to get some feedback from the inspectors for their interpretation.

You are correct in that the weld you indicate is not a CJP. It will be a PJP. CJPs often trigger difficult NDT. The NDT is especially difficult if radiographic or UT is required. Frankly, I do not know of an easy NDT for this particular kind of weld. That is another reason that I prefer to require visual inspection. The inspector will observe the set up and the process to assure that the engineer gets the effective weld indicated. Another challenge is that the flange thickness varies. That is why I indicate the E to be the material thickness minus 1/8".

I prefer not to show the angle, root opening, or process. I leave that up to the shop and only show the effective thickness that I know that the shop can provide. That makes it easy on the welders, the inspectors, and most of all ...me.

Regards,
Harold Sprague

From: jatech@telus.net [mailto:jatech@telus.net]
Sent: Monday, October 13, 2008 3:52 PM
To: seaint@seaint.org
Subject: Re: RE: Full Pen Weld at Channel

For the last 45 years I have called for a square butt weld on both sides of the web and a 60 degree single bevel with zero gap and zero root face along with a backgouge symbol for both flanges. I know it's not a CP weld so I don't call it out as one.

These stringers are also called "cranked" in some areas.

Dave Lowen
jatech@telus.net
Alberta 780.470.5187
California 510.550.7514

On Oct 13, 2008, spraguehope@hotmail.com wrote:

This is a common issue. This is also known as a broke back stair stringer. Be careful so that you get what you intend. If you truly need a full pen weld, then specify what you need. If you get a true full pen weld, you will then have run off tabs and you will have a weld access hole through the web. It will not be pretty.

Now the architect will hate that hole and point out that no other broke back stringer in existance will have a weld access hole, and he will be correct.

You as the engineer have a dillema. Swimming upstream in the world of convention or engineering something that will satisfy most everyone.

I have had this conversation with a lot of welding and fabricating gurus and resoved to the following:
Show a PJP weld symbol with E in the spot indicating the effective weld thickness. In the tail of the weld symbol indicate:

PJP E=MTL THICKNESS - 1/8"
WELD ACCESS HOLE NOT REQUIRED
NDT NOT REQUIRED
VISUAL INSPECTION REQUIRED

Show the same weld symbol for the web weld. Calculate if this is sufficient for the weld you need.

You can have it ground flush if required.

The above weld will have a prepared beveled surface. It will be close to a CJP, but not quite. It will look like all of the other welds out there on stair stringers, but you will have some idea of what you have. The vast majority of these welds existing in the field are just butt welds that are not prequalified and you have no idea of the thickness of the effective weld.

Go to any project where there is a broke back stringer and you will not find a weld access hole even if the weld was specified as a CJP. It makes you wonder what weld was provided. At least with the notes that I now use, I am getting a definable weld and it is inspected.

Regards,
Harold Sprague

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RE: RE: Full Pen Weld at Channel

Dave,

That is pretty much (I think) to what I have called out with the exception of the weld at the web. The detailer is going to ask the fabricator what they would prefer, then I will look at it. May save a step or two.

Joe

From: jatech@telus.net [mailto:jatech@telus.net]
Sent: Monday, October 13, 2008 3:52 PM
To: seaint@seaint.org
Subject: Re: RE: Full Pen Weld at Channel

These stringers are also called "cranked" in some areas.

Dave Lowen
jatech@telus.net
Alberta 780.470.5187
California 510.550.7514

On Oct 13, 2008, spraguehope@hotmail.com wrote:

This is a common issue. This is also known as a broke back stair stringer. Be careful so that you get what you intend. If you truly need a full pen weld, then specify what you need. If you get a true full pen weld, you will then have run off tabs and you will have a weld access hole through the web. It will not be pretty.

Now the architect will hate that hole and point out that no other broke back stringer in existance will have a weld access hole, and he will be correct.

You as the engineer have a dillema. Swimming upstream in the world of convention or engineering something that will satisfy most everyone.

I have had this conversation with a lot of welding and fabricating gurus and resoved to the following:
Show a PJP weld symbol with E in the spot indicating the effective weld thickness. In the tail of the weld symbol indicate:

PJP E=MTL THICKNESS - 1/8"
WELD ACCESS HOLE NOT REQUIRED
NDT NOT REQUIRED
VISUAL INSPECTION REQUIRED

Show the same weld symbol for the web weld. Calculate if this is sufficient for the weld you need.

You can have it ground flush if required.

The above weld will have a prepared beveled surface. It will be close to a CJP, but not quite. It will look like all of the other welds out there on stair stringers, but you will have some idea of what you have. The vast majority of these welds existing in the field are just butt welds that are not prequalified and you have no idea of the thickness of the effective weld.

Go to any project where there is a broke back stringer and you will not find a weld access hole even if the weld was specified as a CJP. It makes you wonder what weld was provided. At least with the notes that I now use, I am getting a definable weld and it is inspected.

Regards,
Harold Sprague

******* ****** ******* ******** ******* ******* ******* *** * 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: Is it a Braced Frame or Cantilevered Column?

Casey,

Good Idea! However, the columns are shoehorned into a frame wall which is perpendicular to the plane of the steel frame. The pedestal would be “thin” at the base of the column. I’m not sure I could take out the base plate forces and design the anchor bolt embedments with the thin pedestal.

Almost worked though..

Joe

From: Casey K. Hemmatyar [mailto:khemmatyar@gmail.com]
Sent: Monday, October 13, 2008 3:08 PM
To: seaint@seaint.org
Subject: RE: Is it a Braced Frame or Cantilevered Column?

I can't see why not, provided you analyze and design it as two story frame.
However can you raise your concrete foundation 4 feet, so your columns rest directly on a concrete "Pedestal"?
With doing this you can have a 11 feet columns with a 7 feet beam span and have simplified the work.

If your drift is high, then with concrete "Pedestals" you can consider a "Diagonal" brace and design it as an OCB rather than a OMRF.

On Thomas Hunt's note, I thought of the same thing. If you have a brace coming into the middle of your column, it would look like a K-Brace, wouldn't it?

Casey K. Hemmatyar, SE

-------- __o
------ _\ <,
----- (_)/ (_)

____________________________________________________________________________________________________________
From: Joseph R. Grill [mailto:jrgrill@cableone.net]
Sent: Monday, October 13, 2008 2:27 PM
To: seaint@seaint.org
Subject: RE: Is it a Braced Frame or Cantilevered Column?

Good Lord, I hope not! Actually, I have been thinking about it since I posted the question. Tell me if I'm crazy (some have in the past), but, if you have a horizontal member at the 4ft elevation and that is where the lower end of the braces are located at the intersection of that horizontal and the columns (note the columns are only about 7ft apart and about 15 ft high), then the moment diagram for the column should be "shaped" similar to a rigid frame, with the difference the "beam" at the top of the frame is very deep (height of the columns less 4ft). Therefore I think you could design with an R=3.25, due to the "braced frame" portion of the frame rather than having to use an R=1.25 for a cantilevered column system.

Yes, no, maybe?

Joe

Joseph R. Grill, PE

From: Tom.Hunt@fluor.com [mailto:Tom.Hunt@fluor.com]
Sent: Monday, October 13, 2008 2:09 PM
To: seaint@seaint.org
Subject: Re: Is it a Braced Frame or Cantilevered Column?

Joe,

Not that I would wish this on anyone, but could this be an Eccentric Braced Frame?!

Thomas Hunt, S.E.
Fluor

"Joseph R. Grill" <jrgrill@cableone.net>
10/13/2008 12:41 PM
Please respond to seaint To <seaint@seaint.org>
cc
Subject Is it a Braced Frame or Cantilevered Column?

I have a braced frame (residential design) location in a SDC D. Dead load weights for the structure will allow me to use an ordinary braced frame. However due to architectural considerations (a hearth opening where the frame is hidden within a framed fireplace) I am trying to raise the lower connection of the braces above the elevation of the hearth opening. I'm not sure if it can still be considered a braced frame (for R values) of if it should be considered a cantilevered column even though it really isn't cantilevered (no fixed base for moments).

Or is it something all together. Of course I would rather consider it an ordinary braced frame rather than cantilevered as the lateral loads are much less.

Thanks again.
Joe

Joseph R. Grill, PE
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RE: Full Pen Weld at Channel

Thanks,

I will look into the AWS forum.

Joe

From: Garner, Robert [mailto:rgarner@moffattnichol.com]
Sent: Tuesday, October 14, 2008 6:52 AM
To: seaint@seaint.org
Subject: RE: Full Pen Weld at Channel

Very well said, Harold, thank you!

The AWS also has a forum of welders that can also give you great insight.

Bob Garner, S.E.

From: Harold Sprague [mailto:spraguehope@hotmail.com]
Sent: Monday, October 13, 2008 2:56 PM
To: seaint@seaint.org
Subject: RE: Full Pen Weld at Channel

This is a common issue. This is also known as a broke back stair stringer. Be careful so that you get what you intend. If you truly need a full pen weld, then specify what you need. If you get a true full pen weld, you will then have run off tabs and you will have a weld access hole through the web. It will not be pretty.

Now the architect will hate that hole and point out that no other broke back stringer in existance will have a weld access hole, and he will be correct.

You as the engineer have a dillema. Swimming upstream in the world of convention or engineering something that will satisfy most everyone.

I have had this conversation with a lot of welding and fabricating gurus and resoved to the following:
Show a PJP weld symbol with E in the spot indicating the effective weld thickness. In the tail of the weld symbol indicate:

PJP E=MTL THICKNESS - 1/8"
WELD ACCESS HOLE NOT REQUIRED
NDT NOT REQUIRED
VISUAL INSPECTION REQUIRED

Show the same weld symbol for the web weld. Calculate if this is sufficient for the weld you need.

You can have it ground flush if required.

The above weld will have a prepared beveled surface. It will be close to a CJP, but not quite. It will look like all of the other welds out there on stair stringers, but you will have some idea of what you have. The vast majority of these welds existing in the field are just butt welds that are not prequalified and you have no idea of the thickness of the effective weld.

Go to any project where there is a broke back stringer and you will not find a weld access hole even if the weld was specified as a CJP. It makes you wonder what weld was provided. At least with the notes that I now use, I am getting a definable weld and it is inspected.

Regards,
Harold Sprague

From: jrgrill@cableone.net
To: seaint@seaint.org
Subject: Full Pen Weld at Channel
Date: Mon, 13 Oct 2008 08:02:21 -0700

For you steel fabricating welding gurus out there, I am looking a stair stringer that is cantilevered and requires a full pen weld at the joint from the sloped portion of the stringer to the horizontal landing. I think the B-U2 groove weld would be the way to go as there is no requirement for weld tabs. It appears that it can be used at the flanges with the angle and the base metal thickness is unlimited.

Is this what is customarily called for on a full pen weld on a stair stringer or something else? If this is acceptable, can the near side and far side be ground flush?

Thanks,

Joe

Joseph R. Grill, PE

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Stainless Steel Wire hangers for indoor pool

Hi,

A friend of mine has asked me for the information on stainless steel wires commonly used to hang reflected ceilings (lightweight almost 1 psf). He is aware of the possible corrosion problems (SCC and cold forming damages) and the common preferred alloys but someone has suggested the use of Techalloy 625 (low iron) weld wires (AWS A5.14 ERNICrMo-3) to hang the ceiling. The wire is 16 gage (0.06" or 1.5 mm Diameter) and will wrap around the main runner as you would see in a normal T-Bar ceiling.
His question is specifically about the common SS wires used in indoor pools and if the Techalloy 625 has been used before in this capacity but I would appreciate any and all comments.

Thanks,
Reza Dashti P.Eng
Vancouver,BC

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RE: Curved GluLam tie

Mark,

ARCH doesn’t want double tension rods, but I like your idea. I’ll use it in the future.

thanks,

Gordon Goodell

From: Mark D. Baker [mailto:shake4bake@verizon.net]
Sent: Monday, October 13, 2008 11:28 AM
To: seaint@seaint.org
Subject: RE: Curved GluLam tie

Try using double tie rods with Simpson PHD’s, or HD’s or similar connectors on each side of the glu-lam.

Mark Baker

From: Gordon Goodell [mailto:GordonGoodell@harmonydesigninc.com]
Sent: Monday, October 13, 2008 8:50 AM
To: seaint@seaint.org
Subject: Curved GluLam tie

Good morning,

I’m looking for a good connection between a curved glulam roof member and ¾” steel tie rod at the base (@ wall line). It’s ~8 kips. I’d like to drill all the way through and use a bearing plate, but that’s about a 2’ long hole. Any ideas?

thanks,

Gordon Goodell

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RE: Full Pen Weld at Channel

Very well said, Harold, thank you!

The AWS also has a forum of welders that can also give you great insight.

Bob Garner, S.E.

From: Harold Sprague [mailto:spraguehope@hotmail.com]
Sent: Monday, October 13, 2008 2:56 PM
To: seaint@seaint.org
Subject: RE: Full Pen Weld at Channel

From: jrgrill@cableone.net
To: seaint@seaint.org
Subject: Full Pen Weld at Channel
Date: Mon, 13 Oct 2008 08:02:21 -0700

Is this what is customarily called for on a full pen weld on a stair stringer or something else? If this is acceptable, can the near side and far side be ground flush?

Thanks,

Joe

Joseph R. Grill, PE

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