Interaction Diagrams For Wood Stud Walls
Interaction Diagrams For Wood Stud Walls
(OP)
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'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.






RE: Interaction Diagrams For Wood Stud Walls
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.
RE: Interaction Diagrams For Wood Stud Walls
do your charts take into account plate crushing or the 5 psf minimum live load pressure?
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
Presently, the graphs don’t even include load casing as I’m setting it up as a pure capacity monograph. The only load parameters in there are load duration and repetitive member.
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.
RE: Interaction Diagrams For Wood Stud Walls
RE: Interaction Diagrams For Wood Stud Walls
http://www.awc.org/aboutus/staff
I would be interested to hear what AWC says about this question.
Please remember: we're not all guys!
RE: Interaction Diagrams For Wood Stud Walls
- Added some vertical marker lines corresponding to 5 psf and a couple of user defined deflection limits.
- Added some horizontal marker lines corresponding to sill plate crushing and sill plate crushing with the 1.25 increase.
- Tried out a long 2x6 SPF per Charlie. Same trend. Utterly liner if I put the d/6 eccentricity back in there.
You're certainly welcome to my stuff if you speak MathCAD. The sheet runs on the free version.
We may get there but, first, I want to vet my output some more to make sure that it's not a KootK thang.
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.
RE: Interaction Diagrams For Wood Stud Walls
For deflection are you considering the min. eccentricity moment or just the lateral pressure?
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
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.
RE: Interaction Diagrams For Wood Stud Walls
Scratch that the axial capacity doesn't look right on mine currently
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
Full Res Image
python code updated with corrections on my github page
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
Woodworks capacity at Cd =1.0:
full res diagram
github updated to include the deflection limits 360,240, and 180
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
An interesting feature of these graphs is the steep rise in axial capacity as wind pressure and moment drop off. Inclusion of an eccentricity of d/6 straightens that portion of the graph out entirely which gives me the impression that consideration of some axial eccentricity is wise.
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.
RE: Interaction Diagrams For Wood Stud Walls
for most my "goal seek" stuff so far I don't anticipate any inflection points so bisection method works well enough and with reasonable computation time for my needs and well if I'm being honest I coded it once got it to work and basically tweak than initial function to fit my new needs.
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
1) What condition does the diagonal line represent?
2) The defection scale on the right. Mispan deflection due to load eccentricity? The graph itself doesn't seem to include that.
I want these sexy features for my graph but first I need to figure out what they are.
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.
RE: Interaction Diagrams For Wood Stud Walls
Top horizontal line is plate crushing with Cb applied. Bottom line is plate crushing where Cb=1.
Vertical lines are l/360, l/240, l/180 deflection limits.
I'm about 75% thru programming a gui for this as well. Added in Fire Retardant option last night will also be adding in shear check and min ecc. Inclusive of deflection.
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
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.
RE: Interaction Diagrams For Wood Stud Walls
added Fv and Fv' calcs to the base wood wall class
here is an example of what the GUI looks like:
Koot I'm probably not the one to lean to for any program learning I picked python up just a little over a year ago and have been mostly brute forcing my way thru things so not the most elegant or efficient coding. I keep meaning to really dig into the web application side of things but just don't have the time to invest in that right now which is a bit of a bummer. That being said I am always open to helping out just hit me up at the email in my profile.
I'll also throw in the learn python hat, it was a pretty easy transition from excel VBA and some small c++ on my end to python and it so much easier to read. The GUI's I build using TKinter which is very similar to VBA forms.
I have a co-worker who is a bit of a savant with this kind of stuff, hes been big into Jupyter Notebooks lately which supports lots of languages and looks like it might end up filling that web app hole.
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
I'll stop flooding the forum with update posts now, I plan to keep tweaking this check the commits on github if your interested as it will highlight what lines I've changed and I personally like to include comments with each commit stating some change log info:
Hopefully Near Future updates:
-give additional results information like the stresses, interactions, detailed Cp calculation steps in the results text box and give it horiz/vert scroll bars so you can see all the info
-Add the ability to save all the user inputs and open a file with those inputs
-Write out a results text file - likely comma separated for easy import into excel
-plot the deflection with the eccentricity considered and solve for the P-M combinations that yields each deflection limit so those vert lines fall in the proper location on the chart.
-Input validation - ugh not my favorite process
The plate crushing horizontal lines will only show up if they are less than 20% greater than the maximum axial load with Cd=2.0
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
Dik
RE: Interaction Diagrams For Wood Stud Walls
Tkinter it comes bundled with most python distributions. to get the tabs you need to import the ttk modules which adds several additional useful widgets.
The plotting is done with matplotlib and embedding a figure into a canvas element
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
I didn't realise that Python was that evolved...
Dik
RE: Interaction Diagrams For Wood Stud Walls
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
Don't hold back on my thread's account. You've answered my question more convincingly than I could have hoped for. And this is interesting.
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.
RE: Interaction Diagrams For Wood Stud Walls
Dik
RE: Interaction Diagrams For Wood Stud Walls
If you insist :)
made a bunch of additions the output now includes capacities at various stud spacings, added a P-M curve which is nearly identical to the P-Pressure Curve with the exception that it plots mid height deflection inclusive of the eccentric moment.
See it in Action: full res animated gif
Common Capacities:
For those hesitant to install python I have compiled the gui to run stand alone on windows systems: OneDrive
it is a 50mb +/- zip file that will uncompress to nearly 140 mb
there will be a lot of files the one to run the gui is this one:
The first time you run it will take a few seconds so be a bit patient please
Dik:
Not overly familiar with SMath studio but did dig a bit the last time I saw it mentioned. Have you edited the Units.xml file or did you define the in*in relationship in your specific file?
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
Dik
RE: Interaction Diagrams For Wood Stud Walls
Gives you two files a CSV file of the NDS load reduction factor table and a pure text file of the results text box
Everything is saved on your desktop in a 'RESULTS' folder
Compiled File: OneDrive
source code is on my github - linked in my signature
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
Does your program run as an actual *.exe? or as an interpreted tokenised file? Does Python (an interpreter) create a true executable? The exe should run a lot faster.
Dik
RE: Interaction Diagrams For Wood Stud Walls
It runs as an executable(.exe) however if I understand how the compiler I use works correctly the exe file at launch essentially does a real time compile of my python file and all it's associated python files which is why there is a pretty decent delay before you as the end user will see the gui show up, this is mostly because I am using matplotlib for the embedded charts as it has a decent amount of dependencies.
In other words I think your second option it does some form of a tokenized executable.
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
Dik
RE: Interaction Diagrams For Wood Stud Walls
Corrections:
-Deflection calculations for the P-M curve where not correct, the P-M curve was multiplying the plf value by the spacing's inflating the deflection numbers
-Cf was not being calculated for Stud grade lumber greater than 6" nominal depth, per NDS Table Cf should be per No.3 grade when depth is 8" or greater
Additions:
-addition of H/180,240,360,600 horizontal lines to both charts
-addition of eccentric load mid height deflection to P-Pressure Chart
-Automatic generation of PvPressure, and PvM curves for common spacing's of 4",6",8",12",16", and 24". Charts are saved as 11x17 pdfs in the results folder
-Results and Chart file names will indicate if Axial eccentricity was considered
Changes:
-chart y-axis is now in units of lbs/ft (plf)
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
-combined axial and bending with eccentric loads should be checked against equation 15.4-1 not 3.9-3.
all links updated
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
using my 2x16 stud at 12 in as an example - stresses below assume 20 psf and Cd=1.6:
no eccentricity
4ft tall:
CODE -->
30ft tall:
CODE -->
52ft tall:
CODE -->
now looking at the 4ft tall wall again with d/6 eccentricity:
CODE -->
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
User Loads Tab:
PvM-Stud Tab:
all links updated
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
Dik
RE: Interaction Diagrams For Wood Stud Walls
-User Loads - Interaction ratio corrected to be checked against fc/Fc' when M=0 and fb/Fb' when P=0 for case when min. eccentricity is not included.
a current base assumption is fv/Fv' won't control but I'm going to add that check in just as a catch all. plan to update the ratio text to indicate what NDS equation it checked against/controlled to make manual back checks easier. So next update the ratio text will read something like
CODE -->
edit: apparently when I said future updates I meant in the next half hour
all links updated
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
-(2)2x and (3)2x stud options added per NDS 15.3.2 Cp for properly connected built up columns is Kf * Cp base assumption for stud walls is sheathing provides full bracing to the short face so Kf is per Le1/d1 so = 1.0. therefore properly nailed/bolted built up 2x studs can be calculated as if they are a solid section.
-spacing optimization will not provide spacing smaller than the actual stud width and will now report spacing's to the nearest lower bound 1/4"
additions:
-clarified wall height assumption to indicate design stud height is either wall height or wall height - (x) 1.5" plates
-updated base assumptions to note capacity is inclusive of wall self weight, true supporting capacity is (result - panel self weight)
-self weight is now a user vertical load category - height can be larger than the wall height, useful when looking at multi story walls
correction:
-user loads that produced points where fc > FcE were mistakenly marked as OK as the interaction ratio was -x so less than 1, additional check for fc < FcE added ratio text will indicate if fc>FcE - "100 (fc > FcE)"
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
- As far as I know, this is now the best wood stud wall design tool available on planet earth, P4P or otherwise.
- This, combined with Forte for beams, basically makes it so that I no longer have need of wood specific commercial software.
- You should really reconsider my offer of collaboration. Within this space, I plan to a) have some serious fun b) give back to the SE community substantially c) earn a little passive income. And you're clearly the man for the job. I don't by this "I'm a hack but my friend's really good" business. It if sweetens the deal, I think that I've got another ET'er lined up for the team.
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.
RE: Interaction Diagrams For Wood Stud Walls
Give him a star... I can only give him one...
Dik
RE: Interaction Diagrams For Wood Stud Walls
enhancement:
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
-User Loads - Self Weight was being considered as an eccentric load when eccentricity was considered, it is rational to assume that self weight would apply concentric to the wall panel and not eccentric.
enhancement:
-User Loads - Spacing Optimization - first pass check of 24" o.c. will now occur before the routine enters its loop. 24" is the upper bound for Cr=1.15 to still apply.
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
-can now export the user load results to a csv file
the main export is now a single csv file in lieu of a csv of the nds table and text file of the results
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
Dik
RE: Interaction Diagrams For Wood Stud Walls
Or are you asking if it's possible to get a pdf directly as output from the program? Short answer is yes, long answer is I've barely read the documentation on the syntax for the report module, reportlab, from what i have read it looks like it can be like writing another program on its own.
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
The attached file would appear the same if printed to a colour printer or a *.pdf. I save the *.pdf to my project notes file. Printed directly from excel. I've installed Doropdf on my computer and when printing it comes up as a printer type and just select it and let Windows do the work.
Dik
RE: Interaction Diagrams For Wood Stud Walls
I think the options right now are:
-Learn ReportLab and get a direct pdf output from my program
-Write out an HTML+css fileset for the exports, then convert that html to PDF - there are a couple modules that seem to handle this
-use Matplotlib to plot a blank chart and add text by coordinates - probably a last resort
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
added... when I'm working on a project, I have hundreds of spreadsheets that I use for different tasks. I enter the project data and run the sheet and print it to a pdf. I don't usually leave a copy of my spreadsheet on the company server. I usually use my laptop rather than the company server and copy my pdf created on the laptop to the sub-directory on the company server at the end of the day/project. My laptop is a lot faster... I can be using my laptop before the company desktop has even reached the logon screen.
Dik
RE: Interaction Diagrams For Wood Stud Walls
Printing to a printer, physical or virtual, from within python doesn't appear to be a very easy task.
I work pretty much the same way you do I much prefer a PDF of the output to store on the office server in our calculation folders.
KootK:
count me in for collaboration on future programming endeavors.
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
The comment was not to be a criticism, but, possibly a manner in producing an easy printout of data without having to jump through hoops to get it. I use this often for printouts as noted in my excel example.
What you've done is incredible and has taken a lot of effort, and thanks for posting your source code.
Dik
RE: Interaction Diagrams For Wood Stud Walls
RE: Interaction Diagrams For Wood Stud Walls
No worries wasn't taking what you were saying as criticism. The output side of things is something I keep reading up on, right now you could right click on any of those files and print to your or any PDF printer it'll just be plain text. The hard part, as far as I know, is that "formatted" word for anything beyond new lines and spaces things get a bit tricky.
I kind of have this to a point that I'm ok with it and not seeing anything that immediately jumps out and bugs me. If anybody finds anything they'd like added/corrected please let me know. Easiest method would be to file an issue on github to make it a little easier to track please put [Wood Stud Wall] in the issue title. If you could also give it label that would be helpful too in prioritizing calculation corrections over feature requests.
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
Mathcad file attached well for reference.
Thanks for pushing me to do this as well. These are good little exercises in coding and wood design.
RE: Interaction Diagrams For Wood Stud Walls
Kootk, I refrained from looking at your mathcad sheet until I made mine. We took pretty different approaches in mathcad. Im not a huge function fan for some reason.
RE: Interaction Diagrams For Wood Stud Walls
Functions are really useful at times... might try a few of them to get into the use of them. I'll take a gander at your use of arrays... looks good.
My new calculator, has incredible function capability, but unfortunately, you cannot call a function from a function, subroutine, or a program... cut the ability off at the knees and greatly reduces programmability.
Dik
RE: Interaction Diagrams For Wood Stud Walls
Looked thru your PDF Sticks couple questions:
CL your calculating a value here but the bracing assumption for the stud wall sheathing satisfies the criteria to consider a CL of 1.0
Looks like you've got a second interaction check of (fc/Fce2)^2 + (fb/Fbe)^2 any reason or reference for doing this interaction?
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
I am not a wood person, so I am having this sheet reviewed our wood people as well (they seem to like it so far).
I appreciate the 2nd set of eyes.
In my beam bending design where I calc'd Cl, I was assuming that under a suction load, compression would develop on a face that I did not know if it would have sheathing. Therefore I calc'd Cl. Is this atypical in wood design assumptions? I counted on the sheathing to brace the stud in the column calculations for out of plane buckling.
With regards to your second question, "(fc/Fc)^2 + (fb/Fb)^2 any reason or reference for doing this interaction?"
This was actually a typo of equation 3.9-4 and me getting lazy (not checked in my current setup). Equation should be (fc/FcE2) + (fb1/Fb)^2 < 1.0. Does this equation control in your experience? I might need to add it to the sheet if so.
Thanks,
S&T
RE: Interaction Diagrams For Wood Stud Walls
Looks like they added 3.9-4 in NDS 2012 wasn't aware of that one, seems unlikely to control given the fully braced assumption for the short face of the stud, doesn't hurt to check it though.
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
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.
RE: Interaction Diagrams For Wood Stud Walls
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.
RE: Interaction Diagrams For Wood Stud Walls
RE: Interaction Diagrams For Wood Stud Walls
-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...
Pyro-Guard showed the lowest factors after reviewing against Dricon (http://www.icc-es.org/Reports/pdf_files/ESR-1626.p...) and FRX(http://new.wolmanizedwood.com/wp-content/uploads/2...)
KootK
I'm on board for working on additional programs
Open Source Structural Applications: https://github.com/buddyd16/Structural-Engineering
RE: Interaction Diagrams For Wood Stud Walls
-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
RE: Interaction Diagrams For Wood Stud Walls
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
RE: Interaction Diagrams For Wood Stud Walls
Cl plays a big role on higher Cd curves.
RE: Interaction Diagrams For Wood Stud Walls
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.
RE: Interaction Diagrams For Wood Stud Walls
Good point... never thought much about it, but, it does make sense.
Dik
RE: Interaction Diagrams For Wood Stud Walls
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