Wood Shear Wall Software or Spreadsheets 2

[medeek]

For residential design I typically run with segmented shearwalls that I manually calculate and check using the SDPWS-2008. However, I am wondering what if any specialized software or spreadsheets that others might use for looking at shearwalls (segmented, perforated, force transfer) or possibly recommend. What is common practice in this area?

 

[KootK]

I recommend Woodworks software if you don't already have it. Given the amount of wood that you do, the $1000 investment seems as though it would be worthwhile. It's starting to get good for 3D modelling too. With that being the case, it might be worth it just to streamline load take downs.

My wife designs a lot of wood buildings. She has comprehensive spreadsheets that do all of the calculations including the tie down anchors. Pretty slick. I think it's a must if you're doing it on a regular basis.


The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[JoshPlumSE]

A mechanical guy doing residential shear wall design? That strikes me as odd. Please explain.

Perforated design is easy, you just follow the rules in the SDPWS... like a cookbook. No special analysis, no special detailing.

FTAO (force transfer around openings) is a good bit more complicated. Both in the analysis and in the detailing. There are a few hand calc examples (SEAoC seismic design manual, Breyer, et cetera) out there, but I'm not a fan of any of them. It seems to me that these hand calc methods don't work for any but the simplest of walls.

Personally, I like using an FEM based method for determining the shear in each panel of an FTAO wall. This is automated in the RISA-3D program (disclaimer: I actually work for RISA-3D, so I'm not exactly an unbiased observer). In my opinion the RISA treatment works really well for single shear walls with a wide variety of openings. Much better (and more accurate and rational)than the simplified hand calc methods.

For years I've been telling myself that I need to write up a white paper on the subject comparing the FEM solution to the hand calc examples and pointing out apparent errors in some of their simplifying assumptions. But, I never seem to find the time. Hopefully, I'll finally get around to it this coming year.

 

[medeek]

Typically I look at the unit shear and uplift (neglecting gravity loads, conservative) to determine the sheathing and nail spacing per SDPWS. Based on the uplift I determine the appropriate holdowns to use which brings me to my Simpson catalog. The holdown choice will dictate the thickness of the chord member that I need to nail or screw into (SDS screws) which I have found is usually more than adequate for the tension and compression chord forces I will encounter.

I typically don't look at the shearwall deflections too much unless there is something particularly interesting going on. The shearwall ratio is also checked but since I usually deal with governing wind loads the 3.5:1 is where I'm at for 90% of my projects.

Most of my shearwalls are segmented, so pretty run of the mill calcs. I could use perforated shearwalls more but I've read somewhere in the literature that perforated shear walls tend to have a "brittle" nature to them which makes me a bit less likely to use them.

Basically, up until this point I've utilized the methodology as laid out in Breyer's book for shearwall design which I find fairly comprehensive but I'm looking at ways to streamline the process and automate my calculations. I find a good spreadsheet or calculator not only saves time but also helps eliminate typos and manual calculation errors.

At the same time I don't like a blackbox approach because it is nice to have a good feel for typical numbers, once your loose touch with this you are no longer an engineer but merely a technician.

 

[medeek]

I made the move into the Residential Structural Engineering field about 6 months ago and I've never regretted it once. The only downside is the money is not as good but personal and professional satisfaction is far more important to me at this point.

 

[medeek]

KootK does your wife use Woodworks for a lot of her work or is it more custom spreadsheets? I've looked at Woodworks briefly but maybe I should give it a second more detailed look.

 

[KootK]

She uses it extensively: load take down, member sizing, simple connections, shear walls... If you're an 80 person firm, you probably don't need a license on everyone's computer. If you're a one man show doing a lot of wood, it's a must.

I believe that you bought a $100 foundation book on my recommendation. Now maybe a $1000 software package. Next, you should hire KootK! A mere $100K per annum. What's an order of magnitude or two between friends?

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[manstrom]

Try out woodworks before you buy. I thought it was too input intensive.

When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller

 

[jayrod12]

I find the woodworks series the best available. It is obviously not perfect however with a quick learning curve it is quite functional. No software is perfect.

I haven't done much wood design as of late but when I have jobs with wood I am always using it. Literally always open on my computer during the design stage.

 

[RFreund]

@ Josh - still waiting.

EIT

http://www.HowToEngineer.com

 

[Brad805]

We have been using Woodworks for many years. The shearwalls program is a little clunky in my opinion, but you get used to its idiosyncrasies after a while.

 

[medeek]

For sizing beams and joists I've found that Weyerhauser's Forte and Boise Cascades BC Calc to be pretty good. I've also created my own beam calculator that I still used for simple supported beams. The Woodworks Sizer program seems fairly decent however I agree that the interface is a bit clunky, the other software listed here are better in that regard.

I've been playing with the shearwall program from Woodworks this morning which I think would be the most useful tool for me to add to my growing list of tools however the learning curve is a little steeper on this one, okay much steeper...

 

[medeek]

I've noticed with Woodworks that unit shear is not uniform for all shear panels along the same shearwall. For example if I have two shear panels with one slightly wider than the other the wider one will have a higher unit shear and higher holdown forces. Has anyone else noticed this? Breyer's book makes the assumption that as long as the aspect ration (h/b) is not greater than 2, then the unit shear is generally assumed to be uniform throughout (WSP segmented shearwall).

A confused student is a good student.

 

[SJBombero]

It sounds like Woodworks is distributing the line load according to the ratio of the stiffness of each segment.

 

[medeek]

My inexperience is showing. Under settings there is an option to distribute the forces to the different panels based on deflection or assume equal rigidity, among a host of other options. It actually looks like a pretty decent piece of software. I could definitely see the utility with more complex structures where the manual calcs would get tedious. Its ability to crank out the wind loads is impressive. I was just comparing the envelope procedure wind loading to my own wind load calculator and it matches perfectly except for a small discrepancy when a windward overhang is present. I've probably got it wrong in my own calculator but I haven't determined what is causing the difference yet. Details like this bug me so I'll probably be up all night until I figure it out.

A confused student is a good student.

 

[medeek]

Just one other interesting point. Take a 30 x 30 x 10 building with a 6/12 gable roof. If you compare the wind loads in Woodworks the directional procedure gives loads that are 150 - 170% larger than the envelope procedure. I never realized there was such a discrepancy between the two methods. So which is more correct for a typical residence? They can't be both correct not when they differ by such a large margin.

A confused student is a good student.

 

[mike20793]

Does Woodworks design the diaphragms for additional forces caused by irregular (non-rectangular) diaphragms and partial depth shear walls/collectors in flexible diaphragms? I've found the only way to properly account for the additional forces is to use transfer diaphragms as outlined in the visual shear transfer method. The Wood Products Council (also called WoodWorks) has some good white papers about this method, so I was curious if the software from AWC incorporated it (they are contributors to the Wood Products Council). It can get pretty daunting for complex layouts, but it helps develop a "feel" for the load path through irregular diaphragms. Software that could calculate the discontinuous chord forces, transfer diaphragm shears, etc. could save a lot of time.

For what it's worth, the Wood Products Council recommends RISA for wood design. I've had good success with using it for some Force Transfer shear walls, but most of my wood design is done in spreadsheets.

 

[manstrom]

Yes, there is a big difference in simplified wind loading vs. analytical wind loading. It is not little. I am told that this is due to measured data vs. calculated (conservative data). Once you get over 60', your loads jump up.

You are getting into the nitty gritty of wood shear wall design. In my opinion, it is one of the most complicated designs that you can get into.

There are a lot of assumptions that you can make that can make the design range greatly: Are shear values distributed assuming flexible or rigid? or both? or semi-rigid? Is shear distributed to walls by stiffness or by linear foot? How is stiffness calculated? 3 factor equation or 4 factor equation?

I'm working on 5+ story wood structures in 110 mph wind areas and I'm making my best guesses. Add in the fact that your exterior walls are 90% glass, and you can see the problem.

It is extremely complicated since the walls are not monolithic and there are many moving parts. Woodworks has a taken a lot of these variables into account as user settings.

I have looked at RISA and was not impressed. Woodworks was clunky for me, although I intend to give it another shot. I do hand calcs combined with some big spreadsheets. I do wind distribution based on a flexible diaphragam for the wide sections and rigid for the narrow sections.



When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller

 

[medeek]

My next job is a shearwall nightmare. Using a flexible diaphragm there is no way for this residence to calc. out, at least not without some very expensive steel moment frames. I am seriously thinking of biting the bullet and purchasing a license for Woodworks and see if I can get it to make this particular floorplan work.

A confused student is a good student.

 

[medeek]

Can RISA 3D generate the seismic and wind loading to shear walls like the Woodworks software?

A confused student is a good student.