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]

@Jsyrod: great advice on the steel. I'm going to test it out this afternoon.

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.

 

[manstrom]

This is the same story on almost every single family home.

Contractors claim that they have "been doing it this way for years". Meanwhile, they don't consider the code updates, improvements in technology, open floor plans, floor to ceiling windows, etc. Houses are not the same floorplan as they used to be, but construction mentality is the same.

Unless it is a custom home, contractors hate the Simpson frames.

medeek, you are too good of an engineer to do the crappy engineering required to make these things look like they work. I don't like working on these things because of situations like this. A near impossible problem, properly solved. However, the solution isn't affordable. Some of the younger engineers here deal with houses like this and I don't know how they make it work without doing something wrong. If I point out an error, I am rocking the boat.

Imagine the same house, but 16' wide with a tuck under garage and 4 stories tall (townhouse). And they are building 100 of them.

A few suggestions:
-Use envelope wind loading, it is much less than analytical wind pressure
-Take all the code reductions that you can get or loading. I don't know where it's located, but you may be able to neglect seismic.
-If possible, use prescriptive IRC design (might not work on this one)
-Try a FTAO frame at that exterior wall. If you can find 2', you can make something work
-Beef up some interior walls to allow the diaphragm to cantilever
-Next time, get with the architect early on and ask for some wall segments to use for shear walls. A lot of time, the Simpson walls are a good "threat".

I didn't read the entire thread, so forgive me if some of this was addressed.



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

 

[JoshPlumSE]

Doing a little bit of research into recent structural failures can help with that contractor. Put on your "educator" cap and point him towards some examples of similar buildings that failed in past events.

"Yes, a lot of people have done it this way for the last 30 years. Then people died in Northridge or Andrew (or whatever). That's why engineered buildings are not designed that way anymore."

 

[manstrom]

Agreed, Josh.

But it's hard to do that when the contractor points across the street and says "same house".

I usually respond with either "Nobody questions my design when they are hiding in a closet during a hurricane" or "It won't be the first time that someone has been doing it wrong for 30 years" if I want to be a jerk.

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

 

[KootK]

I attended an insurance seminar recently were the presenter was very down on residential work, including condo towers. Statistically, the fees are the lowest and the chances of getting sued are the highest. Apparently lawyers, actuaries, and MBA's know better.

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.

 

[medeek]

I'm going to talk with the contractor today and see if I can discuss things a little with him.

I have thought of using the "Envelope" method in the Woodworks software for the analysis however with such crazy geometry and all of the re-entrant corners I was of the understanding that it should not be used in these situations.

Typically I like to envelope the design by taking the largest shear loads due to rigid or flexible diaphragm analysis per Breyer's suggestion in his text, however maybe this is too conservative? Wind loads in this region generally govern, on this design it was all wind.

I think I probably need to be more assertive with the designer and alter the design if it comes to it. A lot of his designs he has been building for years have problems like this one, no room for shearwalls on half of the house or worse. I know that I can make a three sided system or cantilevered diaphragm work but based on empirical data from previous earthquakes we know that they are not going to be as strong as they would be braced on four sides.

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[KootK]

I'd be inclined not to sweat the seismic really. Wood frame houses do very well in earthquakes. And, in my opinion, that has relatively little to do with any engineering attention that they may have received.

You previously mentioned that you think you suffer some for not having a day-to-day mentor. I suspect that you're right about that. There are a lot of mixed messages out there. All of the literature tells you how to do it by the book and that you should do it by the book. Industry tells you to compromise. This is somewhat institutionalized by IRC and Part 9 in Canada.

I wish that they'd help us out by expanding the scope of these documents. Just say something like "all walls must be 30% solid or tied down with engineered hardware." Leaving the enforcement of good engineering practice to engineers has never been a great formula. Just ask California. I wear khakis to work, not a cape.



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.

 

[jayrod12]

I wear khakis to work, not a cape.

This should be your new sig!

 

[KootK]

Perhaps I will. I actually keep a sparkly purple cape at the office left over from a Halloween party. Whoever on the team is getting beat down the worst on any particular day is entitled to don the cape.

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.