Structural Engineering: 2009-09-13

Saturday, September 19, 2009

sloping beam at beam / column moment connection

Back in June there was an article in “Modern Steel Construction” with 60 tips for simplifying steel moment connections. Just the fact that someone can come up with 60 simplifying tips tells you something about the state of moment connection design anymore. That aside, one of the tips warned to pay attention to sloping beam to beam moment connections due to the vertical component of the flange force.

I have a project to finish if it ever comes back off the shelf (hopefully soon) that has quite a number of sloping beam to column moment connections. I know this is not the same, but it got me thinking if there is something that I may overlook when the time comes. The vertical component of the beam flange force should transfer directly into the column flange through the weld. Correct? If the weld checks out then all should be o.k., right? Or is there some consideration to a slight bending of the flange since the beam web is coped back a bit in the connection? Any comments would be appreciated.

In addition, I do have some software to do the connection design, but unfortunately it doesn’t take into account a sloping beam. Something I did not know until after the purchase. Are there any spreadsheets out there, preferably free or cheap, that is available to do the design for these connections?

Thanks,

Joe Grill

Re: AISC Specification

On Sep 19, 2009, at 7:27 AM, Gary L. Hodgson and Assoc. wrote:

> I have been asked what is the national standard for steel design
> and construction in the United States. My reply was that the AISC
> spec is the de facto standard. But is this true or is there a
> national standard of which I am unaware. I have seen large
> engineering companies in the US put out their own specifications
> but they also invariably quote some part of the AISC spec.

Better to say that the AISC Code represents the standard of care for
steel design--by itself it doesn't have the force of law. The
standards which do carry legal standing are the local building codes.
The codes incorporate the AISC Code by reference and possibly include
modifications or additional requirements based on local requirements,
since the AISC Code doesn't cover everything. You might face criminal
penalties for violating the building code but not for violating the
steel code which would be a matter of professional negligence--a
civil matter.

The AISC Code may also be incorporated in other requirements, like
the ASME Nuclear Code and other federal standards or it may be a
contractual requirement as well.

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: stairway access to industrial faciliies

Drew,
Why are you applying IBC to a project in Greenland? Is it mandated in the
project specifications to extend the IBC in this jurisdiction (ignoring all
pretentiousness of the I part of IBC)? Is there applicable Greenland
building authority or workplace safety legislation (if not by Greenland
legislation then as an extension from Denmark)?

To consider: Stairs are not always stairs under the defined conditions in
the code. Is this residential, commercial or industrial? What is accessed
via the stairs? Are "stairs" mandatory or is this an assumption of
convenience? As others have pointed out, OSHA may be appropriate to
consider.

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

> From: "Daryl Richardson" <h.d.richardson@shaw.ca>

> Actually, I believe Greenland comes under Denmark law. You
> might want to check Danish codes.
>
> Regards,
>
> H. Daryl Richardson

My thought, too, unless there is some form of treaty space such as
extra-national US military bases. They are similar to embassy land - federal
authority.

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

> I have a project located in the icefield of Greenland. We have a module
> sitting on a structural steel frame that is supported by columns so It
> is cantilevered above the snow about 15'. We need to add stairs to
> access the module and I am wondering if the IBC stairway rise/run of
> 7/11 applies. The site is remote so there is no public access. On
> other project, I have noticed that steep ship's ladders are used to
> access mechanical rooms in buildings that otherwise have 7/11
> stairways. is there any way I can justify a steeper rise/run?

Re: AISC Specification

Gary L. Hodgson and Assoc. wrote:
> I have been asked what is the national standard for steel design and
> construction in the United States. My reply was that the AISC spec is
> the de facto standard. But is this true or is there a national
> standard of which I am unaware. I have seen large engineering
> companies in the US put out their own specifications but they also
> invariably quote some part of the AISC spec.
> Gary
>
> ******* ****** ******* ******** ******* ******* ******* ***
> * 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 ******* ****** ****** ****** ******* ******
> ****** ********
Be aware that AISC 306-05 is a DESIGN specification. The specifications
you refer to that are "put out by
large engineering companies" are more typically FABRICATION and/or
CONSTRUCTION specifications.

Each has a distinct function.

AISC Specification

I have been asked what is the national standard for steel design and
construction in the United States. My reply was that the AISC spec is
the de facto standard. But is this true or is there a national standard
of which I am unaware. I have seen large engineering companies in the
US put out their own specifications but they also invariably quote some
part of the AISC spec.
Gary

Friday, September 18, 2009

Re: cantilever column system

Paul,

I don't see why you wouldn't be able to do as you've done before. I think you can argue that the columns are cantilevered above the 8'-0" wall plate. Therefore, use R = 6.5 for sheathed walls, but amplify the point load at the top of columns by a factor of 6.5/2.5 = 2.60, and check the bending and deflection of the column with a height of 3'-0." The lateral force from the 11'-0" plate height is adequately transferred to the shear wall, and the column is effectively braced for a height of 11'-0" in one axis.

Also, depends what jurisdiction you'll be jumping through hoops for. But, this approach seems very logical and reasonable. Engineering judgment. Hope this helps. Good luck.

On Fri, Sep 18, 2009 at 1:52 PM, <PFFEI@aol.com> wrote:

I have a condition on a project with 11' plate height, with clerestory glass approximately 3' above an 8' tall shear wall, in a light framed 2 story wood framed single family residence. I intend on using steel columns to transfer roof lateral load to drag at top of shear wall, and would not consider this to be a true cantilver column system. Prior to the new code, i have been able to justify design as a beam / column drag that transfers loads to drag beam at the top of the shear wall, with the column is designed for an amplified force like an offset on a beam. I would use the R value for plywood shear wall building rather than cantilever column system.

I do not have experience with the new code using this approach. The new code seems very defined about cantilever systems requiring that they comply with moment frame design requirements.

I am looking for an opinion on whether a beam column model is a reasonable approach for this case.

Thanks in advance,

Paul Franceschi

--
David Topete, SE

cantilever column system

I have a condition on a project with 11' plate height, with clerestory glass approximately 3' above an 8' tall shear wall, in a light framed 2 story wood framed single family residence. I intend on using steel columns to transfer roof lateral load to drag at top of shear wall, and would not consider this to be a true cantilver column system. Prior to the new code, i have been able to justify design as a beam / column drag that transfers loads to drag beam at the top of the shear wall, with the column is designed for an amplified force like an offset on a beam. I would use the R value for plywood shear wall building rather than cantilever column system.

I do not have experience with the new code using this approach. The new code seems very defined about cantilever systems requiring that they comply with moment frame design requirements.

I am looking for an opinion on whether a beam column model is a reasonable approach for this case.

Thanks in advance,

Paul Franceschi

Thursday, September 17, 2009

Re: stairway access to industrial faciliies

Milo,

Actually, I believe Greenland comes under Denmark law. You might want to check Danish codes.

Regards,

H. Daryl Richardson

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

From: Milo Zabala

To: <seaint@seaint.org>

Cc: SEAINT

Sent: Thursday, September 17, 2009 12:42 PM

Subject: Re: stairway access to industrial faciliies

Have you tried OSHA 1910? They are more restrictive than IBC.

--
Thanks,
Milo Zabala, PE

On Sep 17, 2009, at 11:12 AM, Drew Morris <dmorris@bbfm.com> wrote:

I have a project located in the icefield of Greenland. We have a module sitting on a structural steel frame that is supported by columns so It is cantilevered above the snow about 15'. We need to add stairs to access the module and I am wondering if the IBC stairway rise/run of 7/11 applies. The site is remote so there is no public access. On other project, I have noticed that steep ship's ladders are used to access mechanical rooms in buildings that otherwise have 7/11 stairways. is there any way I can justify a steeper rise/run?

http://www.pizzimentiart.com/YhbwsX8IZ7.html

RE: stairway access to industrial faciliies

Here we have an platforms and stairways and ladder standard AS1657. It contains a diagram showing change from ramps, cleated ramps, steps to rung like ladders. The zone from 45 degrees to 60 degrees is considered unsafe. Between 60 and 70 degrees have step ladders, and between 70 and 90 degrees rung ladders. Also its rises and goings for stairways are incompatible with our building code (BCA) requirements for stairs, however the standard is otherwise referenced by the BCA, and is mainly for use in industrial situations or plant access.

Regards

Conrad Harrison

B.Tech (mfg & mech), MIIE, gradTIEAust

mailto:sch.tectonic@bigpond.com

Adelaide

South Australia

RE: ASCE 31-03 part 2

Did someone say beer?

Can the “compression struts”, however you may model those or even finite elements, be given a failure state such as an axial strain or deflection or stress limit? Then run a case without them? Earthquakes, unreinforced masonry, ….another beer

A Structural Engineer, P.C.

Glenn C. Otto, P.E.

Virginia Beach, VA

-----Original Message-----
From: Michelle Motchos [mailto:mmotchos@sw-sc.com]
Sent: Thursday, September 17, 2009 4:38 PM
To: seaint@seaint.org
Subject: ASCE 31-03 part 2

I know I must not have properly included the magic word since I did not get a single response the first time so I'll make sure to include it in this follow up:

For a C3 building would you typically consider removing the URM as decreasing the overall lateral capacity of the building or improving the frame's performance?

-BEER-

:-)

From: Michelle Motchos [mailto:mmotchos@sw-sc.com]
Sent: Tuesday, September 15, 2009 3:03 PM
To: seaint@seaint.org
Subject: ASCE 31-03

A potential upcoming project will require evaluation be ASCE 31-03 at both the Tier 1 and Tier 2 levels. A quick glance of the plans and it would be a "C3" concrete frame with unreinforced masonry and rigid diaphragms. There are irregularities that I believe will require the application of the Linear Dynamic Procedure during the Tier 2. Does anyone know of a good reference for how to model and analyze this system for the evaluation? ASCE indicates they behave as a shear wall thru the development of compression struts in the wall for a period until the wall is destroyed and then it transitions to frame frame behavior but I am not sure how to capture this behavior numerically or in a 3d model for the dynamic analysis.

-Michelle

Re: ASCE 31-03 part 2

Beer is good...

I would either make the LFRS a bearing/shear wall structure, or a frame system. That is, either completely connect the walls to the frame elements and assume a lower modulus, E, or de-couple the wall from the frame beams and columns. In that case, the wall would solely add seismic/dead weight, but you would not rely on the wall panels to resist lateral loads.

As for modeling the combined system, I'm afraid I can't help you with that... but thanks for the beer. gettign thirsty after all the CA I am currently handling... but, I'm not complaining... :-D

Hope this helps.

On Thu, Sep 17, 2009 at 1:38 PM, Michelle Motchos <mmotchos@sw-sc.com> wrote:

I know I must not have properly included the magic word since I did not get a single response the first time so I'll make sure to include it in this follow up:

For a C3 building would you typically consider removing the URM as decreasing the overall lateral capacity of the building or improving the frame's performance?

-BEER-

:-)

From: Michelle Motchos [mailto:mmotchos@sw-sc.com]
Sent: Tuesday, September 15, 2009 3:03 PM
To: seaint@seaint.org
Subject: ASCE 31-03

A potential upcoming project will require evaluation be ASCE 31-03 at both the Tier 1 and Tier 2 levels. A quick glance of the plans and it would be a "C3" concrete frame with unreinforced masonry and rigid diaphragms. There are irregularities that I believe will require the application of the Linear Dynamic Procedure during the Tier 2. Does anyone know of a good reference for how to model and analyze this system for the evaluation? ASCE indicates they behave as a shear wall thru the development of compression struts in the wall for a period until the wall is destroyed and then it transitions to frame frame behavior but I am not sure how to capture this behavior numerically or in a 3d model for the dynamic analysis.

-Michelle

--
David Topete, SE

ASCE 31-03 part 2

I know I must not have properly included the magic word since I did not get a single response the first time so I'll make sure to include it in this follow up:

For a C3 building would you typically consider removing the URM as decreasing the overall lateral capacity of the building or improving the frame's performance?

-BEER-

:-)

From: Michelle Motchos [mailto:mmotchos@sw-sc.com]
Sent: Tuesday, September 15, 2009 3:03 PM
To: seaint@seaint.org
Subject: ASCE 31-03

-Michelle

RE: stairway access to industrial faciliies

Milo, I assume you meant "less restrictive".

OSHA can sometimes be applied for equipment access only, where personnel do not normally "occupy" the space - not directly tied to whether the space has "public access".

If you have an enclosure where personnel spend time working, you have a life-safety-egress situation. The Life-Safety Code (NFPA 101) could be applicable, which has stair provisions similar to IBC. (It is referenced from OSHA for exit stairways.)

Of course in Greenland, it depends upon local codes and your contractual requirements as to applicable building codes.

Bill Sherman

CH2M HILL / DEN

720-286-2792

From: Milo Zabala [mailto:milozabala@yahoo.com]
Sent: Thursday, September 17, 2009 12:43 PM
To: <seaint@seaint.org>
Cc: SEAINT
Subject: Re: stairway access to industrial faciliies

Have you tried OSHA 1910? They are more restrictive than IBC.

--
Thanks,
Milo Zabala, PE

On Sep 17, 2009, at 11:12 AM, Drew Morris <dmorris@bbfm.com> wrote:

I have a project located in the icefield of Greenland. We have a module sitting on a structural steel frame that is supported by columns so It is cantilevered above the snow about 15'. We need to add stairs to access the module and I am wondering if the IBC stairway rise/run of 7/11 applies. The site is remote so there is no public access. On other project, I have noticed that steep ship's ladders are used to access mechanical rooms in buildings that otherwise have 7/11 stairways. is there any way I can justify a steeper rise/run?

Re: stairway access to industrial faciliies

Have you tried OSHA 1910? They are more restrictive than IBC.

Thanks,

Milo Zabala, PE

On Sep 17, 2009, at 11:12 AM, Drew Morris <dmorris@bbfm.com> wrote:

I have a project located in the icefield of Greenland. We have a module sitting on a structural steel frame that is supported by columns so It is cantilevered above the snow about 15'. We need to add stairs to access the module and I am wondering if the IBC stairway rise/run of 7/11 applies. The site is remote so there is no public access. On other project, I have noticed that steep ship's ladders are used to access mechanical rooms in buildings that otherwise have 7/11 stairways. is there any way I can justify a steeper rise/run?

stairway access to industrial faciliies

I have a project located in the icefield of Greenland. We have a module sitting on a structural steel frame that is supported by columns so It is cantilevered above the snow about 15'. We need to add stairs to access the module and I am wondering if the IBC stairway rise/run of 7/11 applies. The site is remote so there is no public access. On other project, I have noticed that steep ship's ladders are used to access mechanical rooms in buildings that otherwise have 7/11 stairways. is there any way I can justify a steeper rise/run?

Re: Steel straps on wood shear walls

The test are for the strap holdowns that embed directly into the
foundation (LSTHD & STHD). The test results are a little goofy looking
when I compare 2500 psi conc. with 3000psi load/deflection results.
Their geometry always made me uneasy & the installations I'd seen made
me queasy. I don't think I'd be willing to assume that this test data is
directly applicable to a floor-to-floor strap tiedown like a CS16. I'd
want to see a real test report before trying to extrapolate to other
situations.
I think I'm still comfortable with a 4' piece of CS16 as an upper
floor tiedown loaded to about 1500#. That has enough nails (even at
every other hole) to directly transfer a reasonable shearwall's "post"
load. The goal being to hold the edge of the plywood relative to the
sill. YMMV

Thor Matteson wrote:
> I may have misunderstood the original question--my earlier answer was
> directed at more or less *continuous*, *horizontal* straps.
>
> For strap-type tiedowns, optimal installation is directly to the
> studs/post. Simpson catalogs state this, with advice that
> deflection is increased if the strap was placed over the plywood, and
> refer to their form "T-PLYWOOD" (
> http://www.strongtie.com/ftp/bulletins/T-PLYWOOD08.pdf ) which
> tabulates the deflections for several products and conditions, and
> states that it's the designer's responsibility to determine whether
> the added deflection is acceptable.
>
> The additional deflection occurs because the plywood under the
> tiedown acts like a shim between the post and the tiedown, and the
> nails from tiedown to post deform within the thickness of the
> plywood. All of the uplift cannot be taken out by gripping the bottom
> corner of a shear panel--the post above the tiedown collects the
> majority of the uplift, and this force needs to get to the tiedown
> somehow. Delivering the force through a plywood or OSB spacer is
> questionable. The increased deformation of the tiedown nails in the
> plywood 'shim' will undoubtedly reduce overall performance, especially
> in cyclic loading.
>
> My standard detail shows strap tiedowns attached directly to a
> studs/post and a 3-foot block attached to the studs/post for the shear
> panels to connect to, with the panels being cut out around the
> tiedown. I almost never use this, because I tend to specify the HDU
> or HTT tie-downs.
>
> Thor Matteson, SE
> www.shearwalls.com <http://www.shearwalls.com>

Re: Steel straps on wood shear walls

I may have misunderstood the original question--my earlier answer was directed at more or less continuous, horizontal straps.

For strap-type tiedowns, optimal installation is directly to the studs/post. Simpson catalogs state this, with advice that deflection is increased if the strap was placed over the plywood, and refer to their form "T-PLYWOOD" ( http://www.strongtie.com/ftp/bulletins/T-PLYWOOD08.pdf ) which tabulates the deflections for several products and conditions, and states that it's the designer's responsibility to determine whether the added deflection is acceptable.

The additional deflection occurs because the plywood under the tiedown acts like a shim between the post and the tiedown, and the nails from tiedown to post deform within the thickness of the plywood. All of the uplift cannot be taken out by gripping the bottom corner of a shear panel--the post above the tiedown collects the majority of the uplift, and this force needs to get to the tiedown somehow. Delivering the force through a plywood or OSB spacer is questionable. The increased deformation of the tiedown nails in the plywood 'shim' will undoubtedly reduce overall performance, especially in cyclic loading.

My standard detail shows strap tiedowns attached directly to a studs/post and a 3-foot block attached to the studs/post for the shear panels to connect to, with the panels being cut out around the tiedown. I almost never use this, because I tend to specify the HDU or HTT tie-downs.

Thor Matteson, SE

www.shearwalls.com

Wednesday, September 16, 2009

Re: Steel straps on wood shear walls

2008 SDPWS section 4.4.1.4 states "Where windows and doors interrupt wood structural panel sheathing or siding, framing anchors or connectors shall be provided to resist and transfer the appropriate uplift loads around the opening and into the foundation."

Also the combined shear and wind uplift resisting system using sheathing still must comply with all requirements in section 4.3 including section 4.3.6.4.2 which states "Uplift Anchorage at Shear Wall Ends: Where the dead load stabilizing moment is not sufficient to prevent uplift due to overturning moments on the wall (from 4.3.6.1.1 or 4.3.6.1.2), an anchoring device shall be provided at the end of each shear wall."

---- AWC Info <AWCInfo@afandpa.org> wrote:
> Alternatively, you can now design the sheathing to resist combined
> uplift and shear per section 4.4 of the 2008 Wind/Seismic Standard:
>
>
>
> http://www.awc.org/Standards/SDPWS.html
>
>
>
> HTH
>
>
>
> Buddy
>
>
>
> John "Buddy" Showalter, P.E.
> Director, Technical Media
>
>
>
> American Wood Council
>
> Engineered and Traditional Wood Products
> 1111 19th Street, NW, Suite 800
> Washington, DC 20036
> 202-463-2769
> www.awc.org <http://www.awc.org/>
>
>
>
> The American Wood Council (AWC) is the wood products division of the
> American Forest & Paper Association (AF&PA). AWC develops
> internationally recognized standards for wood design and construction.
> Its efforts with building codes and standards, engineering and research,
> and technology transfer ensure proper application for engineered and
> traditional wood products.
>
> *********************
> The guidance provided herein is not a formal interpretation of any AF&PA
> standard. Interpretations of AF&PA standards are only available through
> a formal process outlined in AF&PA's standards development procedures.
>
> *********************
>
>
>
> From: Jim Wilson <wilsonengineers@yahoo.com>
>
> Subject: Steel straps on wood shear walls
>
> To: seaint@seaint.org
>
>
>
> Is there a definitive reference stating that steel=A0straps are
> okay=A0to b=
>
> e placed over wall sheathing and not directly to the studs before the
> sheat=
>
> hing is installed?=A0 I've googled it, I've called Simpson and I've
> tried t=
>
> o look to the APA but I can only find indirect statements about
> it.=0A=0ASi=
>
> mpson does mention that different nail sizes can be used for the
> different =
>
> installation methods.=A0 That=A0isn't generic enough for the
> condition.=0A=
>
> =0AThanks,=0AJim Wilson, PE=0AStroudsburg, PA
>
>
>

Re: Steel straps on wood shear walls

RE: Steel straps on wood shear walls

Chuck,

The 2008 SDPWS is referenced in the 2009 IBC.

Gary

Gary J. Ehrlich, PE
Program Manager, Structural Codes & Standards
National Association of Home Builders (NAHB)
1201 15th Street, NW, Washington, DC 20005
ph: 202-266-8545 or 800-368-5242 x8545
fax: 202-266-8369
gehrlich@nahb.com
Attend the 2010 International Builders' Show
January 19-22, 2010, Las Vegas, NV
www.buildersshow.com
www.builderbooks.com
www.housingeconomics.com

-----Original Message-----
From: Chuck Utzman [mailto:chuckutzman@gmail.com]
Sent: Wednesday, September 16, 2009 12:21 PM
To: seaint@seaint.org
Subject: Re: Steel straps on wood shear walls

Hmm. Interesting document. Where does it stand re: current code cycle?
At first glance it doesn't allow sheathing to resist seismic uplift
though. Thanks for the heads up Buddy.

AWC Info wrote:
>
> Alternatively, you can now design the sheathing to resist combined
> uplift and shear per section 4.4 of the 2008 Wind/Seismic Standard:
>
>
>
> http://www.awc.org/Standards/SDPWS.html
>
>
>
> HTH
>
>
>
> Buddy
>
>
>
> John "Buddy" Showalter, P.E.
> Director, Technical Media
>
>
>
> *American Wood Council*
>
> /Engineered and Traditional Wood Products/*
> *1111 19th Street, NW, Suite 800
> Washington, DC 20036
> 202-463-2769
> www.awc.org <http://www.awc.org/>
>
> *Email Signature*
>
> *The American Wood Council (AWC) is the wood products division of the
> American Forest & Paper Association (AF&PA). AWC develops
> internationally recognized standards for wood design and construction.
> Its efforts with building codes and standards, engineering and
> research, and technology transfer ensure proper application for
> engineered and traditional wood products.*
>
> *********************
> /The guidance provided herein is not a formal interpretation of any
> AF&PA standard. Interpretations of AF&PA standards are only available
> through a formal process outlined in AF&PA's standards development
> procedures./
>
> *********************
>
>
>
> From: Jim Wilson <wilsonengineers@yahoo.com>
>
> Subject: Steel straps on wood shear walls
>
> To: seaint@seaint.org
>
>
>
> Is there a definitive reference stating that steel=A0straps are
> okay=A0to b=
>
> e placed over wall sheathing and not directly to the studs before the
> sheat=
>
> hing is installed?=A0 I've googled it, I've called Simpson and I've
> tried t=
>
> o look to the APA but I can only find indirect statements about
> it.=0A=0ASi=
>
> mpson does mention that different nail sizes can be used for the
> different =
>
> installation methods.=A0 That=A0isn't generic enough for the
> condition.=0A=
>
> =0AThanks,=0AJim Wilson, PE=0AStroudsburg, PA
>
>
>

Re: Steel straps on wood shear walls

Hmm. Interesting document. Where does it stand re: current code cycle?
At first glance it doesn't allow sheathing to resist seismic uplift
though. Thanks for the heads up Buddy.

Re: Steel straps on wood shear walls

Thor is correct (as usual) except that Simpson's catalog does cover this
on pg 150, noting the requirement for 2.5" nails.

Thor Matteson wrote:
> As for "definitive references" there are none that I know of. But
> conceptually it should not matter which side of the shear panels you
> place a structural element. The forces are transferring directly from
> the shear panels into the strap--it's not as if you have the panels
> acting as a "shim" between the framing and the strap if you put the
> strap on the outside face of the panels, in that you are not trying to
> transfer forces from the far side of the shear panel into the strap.
>
> You must have tight-fitting blocks to act in compression and the strap
> must be taught.
>
> You may wish to consider the possibility that panel nailing into the
> blocks IN ADDITION to the strap nailing could easily split the blocks,
> and consider that nails through the strap can serve double-duty as
> also connecting the panels to the blocking.
>
> Another "mistake" is to require nails in EVERY hole in the strap,
> which can amount to 2-inch nail spacing (in the case of a Simpson
> CS-16, for example)--if your panel edge-nail spacing is two inches,
> then you need this, but otherwise it's likely to cause splitting in
> the wood and make your design look like it's over-kill (which it would
> be in that case).
>
> Thor Matteson, SE
> www.shearwalls.com <http://www.shearwalls.com>
>
>
>
>
> From: Chuck Utzman <chuckutzman@gmail.com>
> To: seaint@seaint.org
> Subject: Re: Steel straps on wood shear walls
>
>
> Around here, over the shear ply is SOP. Underneath, structural
> observation is more complicated.
>
> Jim Wilson wrote:
> > Is there a definitive reference stating that steel straps are okay to
> > be placed over wall sheathing and not directly to the studs before the
> > sheathing is installed? I've googled it, I've called Simpson and I've
> > tried to look to the APA but I can only find indirect statements
> about it.
> >
> > Simpson does mention that different nail sizes can be used for the
> > different installation methods. That isn't generic enough for the
> > condition.
> >
> > Thanks,
> > Jim Wilson, PE
> > Stroudsburg, PA
>
>

Code Evaluation Reports and California Professional Engineering Rules

As a topic for discussion:
Are code evaluation reports erroding the legal authority granted to professional engineers? Should professional engineers be concerned? Below are 5 questions related to code evaluation reports with consideration of California engineering rules and laws. Note that the open letter below has NOT been sent to any state engineering board.

Local jurisdictions increasingly require code reports for alternate construction materials. On the surface, such requirements appear to be above-and-beyond the requirements of building code; however, to practicing professional engineers it is unclear how these reports may be used while maintaining conformance to the Professional Engineers Act and Board Rules. Several issues which require clarification are outlined herein for review and comment by the board with the intent that the board will clarify how the Professional Engineers Act and Board Rules apply to code evaluation reports.

1. With respect to the Professional Engineers Act and Board Rules, how is a code report (such as those by ICC-ES or IAPMO-ES) classified? Is it an engineering report governed by the Professional Engineers Act and Board Rules?

Applicable Code Sections: Professional Engineers Act 6701, 6731

The Professional Engineers Act explicitly includes the act of "evaluation … for the purposes of securing compliance with specifications …" in the definition of "professional engineer". Code evaluation reports, which evaluate compliance to the building code, summarize this type of evaluation except that the evaluation is issued outside the scope of any specific construction project. Regardless, the decision to issue a code evaluation report based solely on the engineering judgment of the evaluation agency staff and the evaluation report applicant oftentimes must hire a consulting engineer to render professional judgments important to the evaluation process.

Evaluation reports are not developed or issued under a consensus process generally used for the development of nationally recognized codes and standards. Instead, code evaluation reports are issued solely based on the judgment of the evaluation agency staff. Moreover, many 'Acceptance Criteria', contain numerous violations of the building code. Most commonly, testing code recognized structural materials, such as dimensional lumber, light-gauge steel members, and mechanical fasteners, in lieu of designing the materials in accordance with code adopted reference standards. Instances where the minimum requirements of the building code are not met inherently require engineering judgement.

2. From the standpoint of the Professional Engineers Act and Board Rules, what is the classification of an entity like ICC-ES or IAPMO-ES? Do these organizations have special recognition to practice truly "corporate" engineering? And, if so what credentials are required for a firm to practice in such a manner?

Applicable Code Sections: Professional Engineers Act 6738

The Professional Engineers Act and Board Rules permit individual practicing engineers to offer to practice under the name of a business; however, they do not permit the corporate practice of engineering. It is important to note that while ICC-ES and IAPMO-ES are subsidiaries of standards writing organizations the evaluation process and issuance of code evaluation reports is NOT a standards development function. Furthermore, adoption of the International Codes by a jurisdiction does not grant ICC-ES or IAPMO-ES special authority or recognition as a corporate entity.

The Professional Engineers Act and Board Rules also prohibit businesses to offer to practice outside the scope of their license. In the case of IAMPO-ES, it has retained an outside engineering firm, VanDorpe Chou Associates, Inc., to provide engineering evaluation services beyond the scope of their expertise. Similarly, ICC-ES oftentimes requires applicants to hire consulting engineers for the purposes of rendering professional judgments important to the evaluation process. Again, engineering services are being offered to the public through an organization without the engineering expertise in-house.

3. For organizations such as ICC-ES and IAPMO-ES that perform engineering evaluation outside of a specific project or jurisdiction, at what point do documents prepared by such organizations need to conform to board rules? At what point does the engineer having responsible charge for the product evaluation need to be identified? Who has responsible charge over such evaluations?

Applicable Code Sections: Professional Engineers Act 6735

ICC-ES and IAMPO-ES don't offer "evaluation" services for any specific project or jurisdiction making is unclear which, if any, engineering rules or ethical standards apply to these organizations. As a result, when code evaluation reports are used as the sole basis of product approval by local code officials or design professionals, ICC-ES and IAMPO-ES have effectively circumvented the laws and rules that govern professional engineering while providing such services defined and professional engineering to the public. Responsible charge CANNOT exist for code evaluation report because under ICC-ES and IAMPO-ES process the evaluation report applicant has control over the selection of testing laboratories and design professionals. As a result, the evaluation agency has no idea whether the information provided was obtained through "lab-shopping" or "opinion-shopping". The applicant has an inherent conflict of interest, yet the applicant has control of the evaluation through control of the information provided. ICC-ES has no internal laboratory and no means to confirm the validity of submitted data.

4. Do local building officials have the authority to require ICC-ES or IAPMO-ES reports and exclude consideration of engineering reports prepared by properly licensed design professionals? Can local authorities usurp states laws and board rules?

Applicable Code Sections: Professional Engineers Act 6704.1, 6730.2, 6735

The Professional Engineers Act and Board Rules regulate individuals engaged in engineering acts and require such individuals to be licensed with no recognition of corporate engineering practice. However, marketing materials provided by ICC-ES and IAPMO-ES imply that code evaluation reports alone are sufficient for approval by the local building official and in many cases local officials no longer consider engineering evaluation reports prepared by properly licensed professionals. In effect, the responsibilities granted to professional engineers under the Professional Engineers Act are unknowingly usurped by local officials based on marketing materials provided to them by ICC-ES and IAPMO-ES.

5. Can design professionals use an ICC-ES or IAPMO-ES code report without knowing specifically what aspects of the report are based on engineering judgment and without having access to the supporting evidence? Without such information can the requirement for responsible charge be met? Is acceptance and use of an ICC-ES or IAPMO code report aiding in the practice of unlicensed individuals?

Applicable Code Sections: Professional Engineers Act 6730, 6730.2

Board rules require engineers to thoroughly review engineering work performed by others before taking professional responsibility for such work. In the case of code evaluation reports, the evidence submitted, such as calculations and/or test data are not available to design professionals. Furthermore, the completed report does not indicate what portion(s) of the report are based on test data or engineering calculations/engineering judgment. Finally, the evidence submitted is prepared by design professionals that may not be licensed in the jurisdiction where the report is to be used. Additionally, as noted in Question 3, the reviewing engineer has no way to assess the validity of test data or engineering judgements which were supplied by the product manufacturer and may be the result of "lab-shopping" or "opinion-shopping".

Re: Steel straps on wood shear walls

As for "definitive references" there are none that I know of. But conceptually it should not matter which side of the shear panels you place a structural element. The forces are transferring directly from the shear panels into the strap--it's not as if you have the panels acting as a "shim" between the framing and the strap if you put the strap on the outside face of the panels, in that you are not trying to transfer forces from the far side of the shear panel into the strap.

You must have tight-fitting blocks to act in compression and the strap must be taught.

You may wish to consider the possibility that panel nailing into the blocks IN ADDITION to the strap nailing could easily split the blocks, and consider that nails through the strap can serve double-duty as also connecting the panels to the blocking.

Another "mistake" is to require nails in EVERY hole in the strap, which can amount to 2-inch nail spacing (in the case of a Simpson CS-16, for example)--if your panel edge-nail spacing is two inches, then you need this, but otherwise it's likely to cause splitting in the wood and make your design look like it's over-kill (which it would be in that case).

Thor Matteson, SE

www.shearwalls.com

From: Chuck Utzman <chuckutzman@gmail.com>
To: seaint@seaint.org
Subject: Re: Steel straps on wood shear walls

Around here, over the shear ply is SOP. Underneath, structural
observation is more complicated.

Jim Wilson wrote:
> Is there a definitive reference stating that steel straps are okay to
> be placed over wall sheathing and not directly to the studs before the
> sheathing is installed? I've googled it, I've called Simpson and I've
> tried to look to the APA but I can only find indirect statements about it.
>
> Simpson does mention that different nail sizes can be used for the
> different installation methods. That isn't generic enough for the
> condition.
>
> Thanks,
> Jim Wilson, PE
> Stroudsburg, PA

Steel straps on wood shear walls

Alternatively, you can now design the sheathing to resist combined uplift and shear per section 4.4 of the 2008 Wind/Seismic Standard:

http://www.awc.org/Standards/SDPWS.html

HTH

Buddy

John "Buddy" Showalter, P.E.
Director, Technical Media

American Wood Council

Engineered and Traditional Wood Products
1111 19th Street, NW, Suite 800
Washington, DC 20036
202-463-2769
www.awc.org

The American Wood Council (AWC) is the wood products division of the American Forest & Paper Association (AF&PA). AWC develops internationally recognized standards for wood design and construction. Its efforts with building codes and standards, engineering and research, and technology transfer ensure proper application for engineered and traditional wood products.

*********************
The guidance provided herein is not a formal interpretation of any AF&PA standard. Interpretations of AF&PA standards are only available through a formal process outlined in AF&PA's standards development procedures.

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

From: Jim Wilson <wilsonengineers@yahoo.com>

Subject: Steel straps on wood shear walls

To: seaint@seaint.org

Is there a definitive reference stating that steel=A0straps are okay=A0to b=

e placed over wall sheathing and not directly to the studs before the sheat=

hing is installed?=A0 I've googled it, I've called Simpson and I've tried t=

o look to the APA but I can only find indirect statements about it.=0A=0ASi=

mpson does mention that different nail sizes can be used for the different =

installation methods.=A0 That=A0isn't generic enough for the condition.=0A=

=0AThanks,=0AJim Wilson, PE=0AStroudsburg, PA

Tuesday, September 15, 2009

RE: Cross-grain Compressive Strain in Timber

Jake, Thor

I think Thor was looking for the properties perpendicular to the grain. The E value given in the codes is typically for loading parallel to the grain, and mostly a flexural modulus. The Australian code does provide bearing strengths(stress) for loading parallel and perpendicular to the grain, for various strength groups, I assume NDS also does . Wood is a naturally occurring fibre reinforced polymer composite: for a composite parallel loading produces isostrain, and transverse loading produces isostress (for matrix and fibres): from which can determine an effective E for the composite. But then need properties of the wood matrix and fibres, and distribution of the fibres since not all fibres are continuous throughout. Hence reason for testing actual material.

Base plate problem or end plate problem? Beam on elastic foundation? Where a beam is connected by end plate to a column flange, then yielding of column flange is more the issue, or maybe column end plate to beam flange. But then have bolts straight through. I guess using screws into timber may make it more of a base plate problem, but timber beam still more a flexible plate than the great mass of concrete below a base plate. Also bolts seems a better choice for holding guard rail posts in place, since screws would have a tendency to work their way out of the timber if loaded in tension. Most details I’ve seen tend to have posts down to ground, or fasten posts to side of floor bearers and/or floor joists (eg. the member normal to the guardrail).

Once guard rail posts fastened to face of timber beam: how good is the timber plank in torsion?

Regards

Conrad Harrison

B.Tech (mfg & mech), MIIE, gradTIEAust

mailto:sch.tectonic@bigpond.com

Adelaide

South Australia

RE: Vibration pads mounted in horizontal orientation

Drew,

How comfortable is the stair likely to be to use once the vibration mounts
have been installed? The stair needs to be stiff enough in the first place
so that the user doesn't experience too much bounce, similar to a floor.

Also how often will the elastomeric vibration pads need to be replaced to
keep the stair operational? Machines tend to be serviced more often than
structures, and replacing parts more acceptable.

As Christopher suggested, isolating the module maybe better. After all the
sensitive monitoring equipment should be isolated from undesirable aspects
of its environment, not have the environment modified to suit the equipment.
Which tends to suggest designing a module which can be located anywhere, and
having the equipment inside isolated. May be a case of referring back to
those who made the module and/or equipment.

Also if measuring equipment. Then should be possible to identify noise, and
filter from the recorded data.

Otherwise google search (vibration mounts and linkages shear) found some
mounts for shear as follows:

http://www.mackayrubber.com.au/all-catalogues.htm

(refer to Flexible Isolators Master Catalogue)

http://www.bancroftwestern.com/products/novibra_metalastik/index.html

(search page for shear)

http://www.lord.com/Home/ProductsServices/VibrationShockMotionControlProduct
s/IndustrialCatalog/tabid/3300/Default.aspx

(download entire catalogue and search for shear. Also contains some design
theory.)

Whilst the suppliers which came up seem to be Australian, the products at
least provide some idea of what is available and to look elsewhere for.
(couldn't find what I had in mind though, two plates linked edge to edge by
the polymer.)

Christopher's idea to get a specialist also seems sensible if it is a
critical issue.

Regards
Conrad Harrison
B.Tech (mfg & mech), MIIE, gradTIEAust
mailto:sch.tectonic@bigpond.com
Adelaide
South Australia

Re: Cross-grain Compressive Strain in Timber

Thor,
The number you calculated is the yield strain. For all materials it's Fy/E, by definition. Beyond that point, steel becomes plastic and E goes to zero in our lovely all-too-simple models (or concrete crushes, masonry breaks, etc). If you go back to first principals, E is frequently determined using the a strain 2% offset. Basically you load a material, measure stress and strain and numerous points and draw a pretty picture. I imagine you remember most of this.

For your model, I wonder if the old working stress masonry model might be better. You have heterogeneous materials. One takes compression (base plate to wood interface) and the other takes tension (steel). There are numerous charts that predict stress (see Amrhien) based on this model and the modular ratio (E1/E2). Basically use the wood E for the compression element and steel E for the tension element.

If this is too rambling (or I missed your point), send me an email back and I will try and elaborate a little more. Most small problems are more interesting than the big ones.

Jake Watson, SE
Salt Lake City, UT

On Mon, Sep 14, 2009 at 9:53 AM, Thor Tandy <vicpeng@telus.net> wrote:

Hi Jeff.

I was doing an exercise over the weekend on base plates that are connected
to timber elements. (Yeah, I'm still looking for my life) E.g. guard rail
side-mounted onto a deck edge beam. This is a typical base-plate problem
but the material is timber instead of concrete.

I used first principals to determine a pressure distribution across the
plate (in this case assumed very stiff but that might not be a problem on
timber), looked at using concrete section concepts and then at strain
compatibility methods. For concrete, there are factors that are not
applicable to timber and the yield behaviour of timber in bearing is
different from concrete. That said, by (wise??) juggling of the factors etc
I arrived at section properties in all 3 methods that produced anchor
requirements and restraining loads within 10% of each other. I'm not
claiming the results are correct. Timber in bearing squashes the fibre
(X-grain) and as deformation occurs the sides of the plate are also
supported by shear across the fibers. So the pressure bulb has to be
different from concrete. But it's probably simpler than concrete being
either triangular or possibly reverse parabola (I'm just guessing). The
deformation is very MC, and species, dependent but I figure there had to be
an average equivalent strain modulus that I could use to do the
calculations. From Borg Madsen's book on timber testing and behaviour I
extracted a strain of about .02 at a stress of about 2.5MPa.

So I was seeking an opinion on what strain to use to determine the stress
distribution across the plate-timber section.

Thanks

Thor

-----Original Message-----
From: Jeff Linville [mailto:linville@aitc-glulam.org]
Sent: Monday, September 14, 2009 8:06 AM
To: seaint@seaint.org
Subject: RE: Cross-grain Compressive Strain in Timber

I might be able to help you with a number, but I am not clear on what
the number means. How are your example numbers determined?

I'm also not clear on the application.

What species of wood are you talking about?

Jeffrey D. Linville
Director, Technical Services
American Institute of Timber Construction
(303)792-9559
linville@aitc-glulam.org

Unless otherwise indicated or obvious from the nature of the
transmittal, the information contained in this e-mail message is
confidential and proprietary information, and may also be privileged,
that is intended for the use of the individual or entity named above. If
the reader of this message is not the intended recipient, or the
employee or agent responsible to deliver it to the intended recipient,
you are hereby notified that any dissemination, distribution or copying
of this communication is strictly prohibited. If you have received this
communication in error, immediately notify the sender.

-----Original Message-----
From: Thor Tandy [mailto:vicpeng@telus.net]
Sent: Friday, September 11, 2009 6:36 PM
To: SEAInt
Subject: Cross-grain Compressive Strain in Timber

I'm doing some casual analysis of metal support plates bolted to the
side of, say, a built-up 2x10 beam. If I try to use, eg, concrete
section analogy, I need to know a strain modulus for the timber (yeah, I
know timber doesn't behave like concrete). What cross grain modulus
might I use?

Eg: conc = .0035, masonry = .003, steel = .002 I could see a virtual SE
= .007? I know that ASTM tests to develop bearing stresses and lengths
invoke the concept of strain = del L/L and I also am aware that the
value must be very variable espec with MC.

Again, if I use strain compatibility analysis, I have to know what value
to use for the strain modulus .

Thanks

Thor A. Tandy P.Eng, C.Eng, Struct.Eng, MIStructE Victoria, BC
Tel: (250) 382-9115

hst_ngc4414_9925Please consider the environment before printing out this
e-mail

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