Interaction Diagrams For Wood Stud Walls 8

[KootK]

So I decided that I no longer wanted to be beholden to Woodworks etc and I would make my own stud wall MathCAD sheet. Go me. I wanted it done differently than what I see most folks do though. I wanted to generate interaction diagrams so that, for given project, I could just generate the diagrams for the handful of wall types that I'll use and then pick values from the graphs as needed. The graphs below do this I think. Each line is a different duration factor (0.9,1,1.25,1.6). They are for 2x4 stud grade 92.625" long; wind (psf) on the x-axis and axial (plf) on the y-ais. I've attached a printout of the entire worksheet for the ambitious.

I've spot checked some results and they seem to be okay. What's bothering me is how straight these curves are. The only action is at the top left in the first diagram where things get curvy with low levels of wind pressure. If you include minimum axial eccentricity of d/6 like software often does, even that goes away. That's what's shown in the second graph below.

So my question is this: does anybody have enough experience with wood stud wall interaction diagrams that they could confirm or deny if the results I'm getting look nuts. Considering how straight the lines are, I would have thought that NDS would just simplify the equations to suit. Frankly, if it's this linear, I feel pretty silly for even going to the trouble of making this spreadsheet.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[KootK]

Im not a huge function fan for some reason.

Thanks for your contribution to this SNT. I may alter my approach to match yours. The solve block is fussy and, depending on the input parameters, I sometimes have to tinker with the start and end values. I find that inelegant. I can't remember why I chose to go the route I did. Probably laziness or stuck on coming in with bending and out with axial for some reason.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[sticksandtriangles]

Final iteration of this for me.

Added DCRs as dots onto the nomograph, included output of the DCRs, allowed for manual overwritting of the Cl term to be 1.0 based on engineering judgement.

 

[sticksandtriangles]

PDF attached as well.

 

[Celt83]

small update
-added expansion tags to the embed frames for the charts so they fill the window in all directions when the window expands
-revised default FRT values to match Pyro-Guard ICC-ES report.

http://www.buildsite.com/pdf/hoover/Pyro-Guard-ICC-ES-Evaluation-1481453.pdf

Pyro-Guard showed the lowest factors after reviewing against Dricon (

http://www.icc-es.org/Reports/pdf_files/ESR-1626.pdf)

and FRX(

http://new.wolmanizedwood.com/wp-content/uploads/2016/10/ESR-1159_FRX.pdf)

KootK
I'm on board for working on additional programs

Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

 

[Celt83]

enhancement:
-user option to specify if compression face is braced for bending or not. Double demising walls would be a use case where no sheathing is applied in the air gap between walls thus 5 psf min lateral live load as suction would be in an unbraced condition. Note assumes eccentricity when considered is such that it would create compression on the unbraced face.

all links updated

Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

 

[Celt83]

the CL factor has a pretty decent impact on strength - to the tune of 1,000 lbs+/- per stud with a 2x6 wall
Notice also the significant impact to the Cd = 1.6 and 2.0 curves

braced - CL = 1.0 :

Unbraced:

Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

 

[sticksandtriangles]

Thats what my charts reflect as well celt,
Cl plays a big role on higher Cd curves.

 

[KootK]

It's an interesting trend that you guys have identified. I guess as you start coming up against elastic LTB as your failure mode, the duration factor looses relevance since E is unaffected by load duration. Then the the lines collapse together.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[dik]

It's an interesting trend that you guys have identified. I guess as you start coming up against elastic LTB as your failure mode, the duration factor looses relevance since E is unaffected by load duration. Then the the lines collapse together.

Good point... never thought much about it, but, it does make sense.

Dik

 

[Celt83]

one more tweak added the option to specify blocking height for use in the CL calculation.

KootK yea that is a great point, it's also greatly impacted by the aspect ratio of the stud 2x4 takes less of a hit than 2x6.

Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering