Wood Shear Wall Software or Spreadsheets
Wood Shear Wall Software or Spreadsheets
(OP)
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?






RE: Wood Shear Wall Software or Spreadsheets
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.
RE: Wood Shear Wall Software or Spreadsheets
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.
RE: Wood Shear Wall Software or Spreadsheets
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.
RE: Wood Shear Wall Software or Spreadsheets
RE: Wood Shear Wall Software or Spreadsheets
RE: Wood Shear Wall Software or Spreadsheets
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.
RE: Wood Shear Wall Software or Spreadsheets
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
RE: Wood Shear Wall Software or Spreadsheets
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.
RE: Wood Shear Wall Software or Spreadsheets
EIT
www.HowToEngineer.com
RE: Wood Shear Wall Software or Spreadsheets
RE: Wood Shear Wall Software or Spreadsheets
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...
RE: Wood Shear Wall Software or Spreadsheets
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
RE: Wood Shear Wall Software or Spreadsheets
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
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.
RE: Wood Shear Wall Software or Spreadsheets
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
RE: Wood Shear Wall Software or Spreadsheets
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
RE: Wood Shear Wall Software or Spreadsheets
Are you saying complicated because of lack of wall? or complicated because of many vertical irregularities?
Look in the simpson stron-wall catalogs. You can get away with some pretty slender walls using their systems. Just make sure you design the foundation to take it. They also have moment resisting frames that you can either use, or get ideas from.
RE: Wood Shear Wall Software or Spreadsheets
This first one is a power point presentation that accompanied a webinar on the subject:
http://risa.com/documents/webinars/Wood%20Building...
This 2nd one is a link you You Tube where you can see the actual webinar:
http://youtu.be/3HTtICAWQ5A
Note:
This webinar is very specifically geared towards commercial wood buildings, not residential. In fact, RISA's implementation is geared much more towards commercial structures. The concepts are basically the same as residential. But, the geometry of residential structures tend to be a lot more problematic. Roof modeling with multiple hips and gables and such is always trickier. Also, you have a lot more discontinuities with residential. Meaning that shear walls don't stack nicely, et cetera.
RE: Wood Shear Wall Software or Spreadsheets
The funny thing is the designer told me that even though this particular plan has never been engineered it has been built 5 or 6 times in town and he has never had a problem. Before our new building inspector was hired apparently just about anything and everything flew through their office.
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
An option to also considered is a "3" sided diaphragm if you have no wall on the one side. We use the methodology for hotels sometimes.
RE: Wood Shear Wall Software or Spreadsheets
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
Note I've tentatively notated where I can get some shearwalls in. The walls are 9ft. high.
This one is going to be fun...
Larger Image
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
I seem to recall this type of system failing in some apartment garages during the northridge earthquake. Something where the gravity only system on the open side deflected a good amount then P-Delta effects made it unstable and.... collapse.
RE: Wood Shear Wall Software or Spreadsheets
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
1) Northwest (plan view) bedroom, use the closet wall as a shear wall. Easy to add in a drag truss.
2) For living room elevations, see attached Simpson product for "Raked Wall Applications" as well as typical shear wall applications.
This house isn't THAT bad :)
RE: Wood Shear Wall Software or Spreadsheets
Note that the northeast corner of the master bedroom violates the IRC in that there isn't a minimum width of wall at the corner. I don't have the IRC handy but typically you can't have a small segment of wall at corners without having specialty details to create adequate hold down at the corner against uplift. The fear is that the uplift load at the corner would overwhelm a single stud pack.
I think the IRC has a table that lists minimum widths at corners.
Of course - if a PE designs out the shear walls then the IRC goes out the window.
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RE: Wood Shear Wall Software or Spreadsheets
Are you a licensed structural engineer?
http://design.medeek.com/admin/license.html
RE: Wood Shear Wall Software or Spreadsheets
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
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: Wood Shear Wall Software or Spreadsheets
I'll do it if it's legit to do so. Frankly, I spend more time working through things with you than my supervisors ever did with me. And don't everybody freak out by my offer. If it's legit to do so.
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: Wood Shear Wall Software or Spreadsheets
I've just ordered a copy of Woodworks and I will put the whole structure into it and throw as many shearwalls in as I can and see what I get. I'm hoping to avoid steel moment frames otherwise my designer will probably fire me. :)
KootK, I really appreciate your offer and also all of the advice you continually give me with little or nothing in return. I have found Breyer's book and other texts to be very useful in my transition to the structural field however the input and feedback I have received in this forum from a number of individuals like yourself has far outstripped any book knowledge I have gained thus far. In a couple years after I've broadened my horizons into concrete and steel I might take you up on your offer if it still stands. I've been doing residential work for about 8 months now and I've yet to take the training wheels off even for wood, but I think I'm getting there.
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
If you place a shear wall in the bedroom like I suggested, then the uplift on the Simpson walls shouldn't be THAT bad. Test it and see what happens, should be a pretty quick calc.
The Simpson SB walls are relatively new and a fantastic alternative to the steel strong walls. I have had good success and contractors seem to like them a little more so far.
RE: Wood Shear Wall Software or Spreadsheets
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: Wood Shear Wall Software or Spreadsheets
The ability to cut the Strong-Wall SB is a huge plus, can't do that with a steel strong wall. Okay, I think we have a game plan here, now to execute.
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
On another note, not related to shear walls but beams, Boise Cascade produces a "King Beam". It's a great product and cheaper than other engineered beams if you need something other than a typical glulam. Just thought I would throw that out there since you are relatively "new" to wood design. Lots of designers don't know about it.
RE: Wood Shear Wall Software or Spreadsheets
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
Pardon my ignorance, I've been following your threads and contributing where I can, a lot of your threads involve the lateral design of residential structures. Are you in a seismic zone or are your designs wind dominated?
I only ask as my experience with residential design is no one pays this much attention to the lateral aspect, however I design in a "non"-seismic (I think they classify it as low seismic now) area. Tall walls get installed all the time with about half the amount of connectors you tend to use in your design. How have you found the acceptance of your detailing by the contractors? The ones around here would laugh me out of the office if I gave them a detail like that. I don't disagree with your detailing and I like that you put this much thought and design into your work I just find it a tad hefty in comparison to what I generally see (and people call me conservative).
RE: Wood Shear Wall Software or Spreadsheets
RE: Wood Shear Wall Software or Spreadsheets
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: Wood Shear Wall Software or Spreadsheets
In the Simpson manuals, shear reinforcement and longitudinal reinforcement are required to be designed by the EOR. It is a concern to be aware of and should be checked for loads acting on the concrete in tension and compression.
If medeek has Enercalc, this can easily be done.
RE: Wood Shear Wall Software or Spreadsheets
Good you are in WA or UT. Nowhere to fit insulation. :)
RE: Wood Shear Wall Software or Spreadsheets
There are so many windows anyways that they probably won't notice the minor insulation in the walls.
RE: Wood Shear Wall Software or Spreadsheets
RE: Wood Shear Wall Software or Spreadsheets
I'm not so sure. For me, this would be less about rebar quantity per se and more about detailing in the disturbed regions at the ends. I see the ends as essentially opening and closing frame corner joints. And those are plenty hard to make work when both members of the corner joint are concrete.
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: Wood Shear Wall Software or Spreadsheets
Anyhow it is still a work in a progress, I'm still waiting on the keycodes from Woodworks to get the lateral loads.
For reference:
Basic Wind Speed (Ultimate) = 155 mph
SDS = .98g
Wind speed typically dominates here with single story wood side structures.
Vertical load on columns (P8) is 5,400 lbs. C&C wind load is 51 psf (zone 4), deflection is .55 inches per IBC 1604.3 and IRC Sec. 301.7
Malone's book has some good examples of sizing stemwall foundations below shearwalls and portal frames for bending and shear however this Enercalc software sounds intriguing. I've heard of it but have never looked into it any detail yet. Now might be the time.
I think with a wall of windows the insulation is least of my worries at the moment however as CBSE pointed out some rigid insulation perhaps with some furring should get me there.
CBSE with regards to your corrections I can see what your getting at however with the sheathing I can't guarantee where the builder will put the seams. When the wall is loaded laterally the connections to the SWSB from the two headers will act like a moment frame one will go into tension and the other into compression. Unfortunately, the middle upper window breaks the continuity of the load path slightly but the additional sheathing/wall area through this region should help spread the load.
I'm debating on having them sheath the inside as well but this will be dependent on what kind of shear loads we see.
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
As for wind design, you will be okay using the simplified procedure. I have looked at the woodworks program and demo'd it. What it won't do is give you the ability to look at stepped plate heights and other various discontinuities. It looks like a great program, but I have spreadsheets that do all the wall designs for me.
For your footings, you will most likely need pad footings to accommodate compression loads at the Simpson walls. Many designers miss the need for extra support and detailing at hold-downs.
The woodworks program you purchased is the one with shear walls, connections, and beam/column design?
RE: Wood Shear Wall Software or Spreadsheets
If the building is a nice rectangular structure with only ext. shearwalls then I even have a nice web based app. that will generate all of the shear loads using the envelope procedure here:
Medeek Wind Load Calculator
Unfortunately, most of the structures I look at are not so simple.
With the footings isn't the big concern with bending due to the moments that the Simpson walls will exert on the foundation and not so much the compression? The foundation will tend to break due to flexure where the Simpson wall meets the window.
However, with the columns (P8) I can see the need for pad footings, especially if my cont. footing were to remain at the 12" wide, 6" deep footing that is called out for the rest of the structure. If this were the case then a 24"x24"x12" pad footing at these two locations would probably be suitable.
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
For the wind loads, my opinion is you are making it way too complicated for the size of house you are dealing with. I have used the simplified procedure on homes from 2,000 sqft to 14,000 sqft and many much more complicated than this one. Is it 100% accurate? No, but it works. You are going to spend a lot of time to get close to the same results. Just my opinion.
RE: Wood Shear Wall Software or Spreadsheets
Yes. However, I believe that the flexure issue presents itself more critically as the anchorage issue shown in detail C below. This is the classic opening/closing joint problem in concrete. Hopefully your flexural bars wind up just being a couple of manageable, small diameter bars.
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: Wood Shear Wall Software or Spreadsheets
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
I botched the right hand side crack in my first sketch above. See below for a revision and some supplementary info.
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: Wood Shear Wall Software or Spreadsheets
Listen to Kootk. He's bang on with this one!
RE: Wood Shear Wall Software or Spreadsheets
I really like the KISS principal :) and believe me, I've been told to "KISS" it a lot.
RE: Wood Shear Wall Software or Spreadsheets
EIT
www.HowToEngineer.com
RE: Wood Shear Wall Software or Spreadsheets
There are a few basic "magic" points to Strut and Tie:
- Determine your B and D regions (this is a fancy way of saying "Design beam like sections as beams, and stout/squat sections as Disturbed regions"). In Strut and Tie, B regions are designed like regular beams, with compressive struts and ties parallel and running the length. Your D regions are where the shear span is less than 2 to 2.5 the beam depth.
- 22.5deg minimum strut angle.
- Check your tiess.
- Check your struts.
- Check your nodes (aka anchorage zones, assumed points of stress flow change).
There are some great resources online for learning this. One of my favourites is a paper from IIT in India.
RE: Wood Shear Wall Software or Spreadsheets
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: Wood Shear Wall Software or Spreadsheets
What am I missing that you two are debating this?
RE: Wood Shear Wall Software or Spreadsheets
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: Wood Shear Wall Software or Spreadsheets
I think I may be getting things confused... The bursting forces involved in anchorage design are really geared toward side face blow (or so I think).
Also note that
So where my confusion was...
When looking at KootK's sketch on 26 Dec 14 18:47 and seeing the bursting restraint bars, I was wondering how to calculate how much steel is required there. The answer to that seems to be answered by Widianto and KootK (about 1/4 the tension). However to answer the question of "when is it required and how effective is it" is a bit unknown to me. It seems as though it would be required when side face blow out is an issue. It does not effect concrete break-out strength (which I believe I have confused this part in the past). Widianto states that transverse reinforcement does not prevent side face blow out but does "increase the magnitude of the load that was maintained after s-f-b. He also states that "When it is impossible to provide the minimum edge distance of 6do, the side-face blowout strength should be calculated using Section D.5.4 of the ACI 318-05". So it seems as though you don't really gain any strength from a code standpoint by providing "bursting reinforcement" (aka side face blowout reinforcement.
EIT
www.HowToEngineer.com
RE: Wood Shear Wall Software or Spreadsheets
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
http://design.medeek.com/resources/footing/2014-02...
http://design.medeek.com/resources/footing/2014-02...
I'm still really new to concrete so if you see something completely amiss please let me know. I based my calcs off of the following references:
ACI318-11
ASCE7-10
Simplified Design of Building Foundations by James Ambrose
Design of Reinforced Concrete 7th Edition by James K. Nelson
The Analysis of Irregular Shaped Structures by R. Terry Malone
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
I used the more conservative directional procedure rather than the envelope procedure. As I have found with my own manual calcs the seismic for a one story building does not govern in my locality, wind speeds are 155mph (ultimate).
As you will note, I was unable to correctly model the diagonal walls since Woodworks does not provide this capability. Perhaps someone has a suggestion in this regard or a better method for simplifying the analysis.
I've manually calculated wind loads on cut up roofs on other projects similar to this however my diaphragm loads were probably never quite this granular. There is something to be said for just putting in the geometry and having the program spit out the entire load take down. It still worries me a little as to how the program distributes the loads to the shear walls, I guess I'm not a fan of black box results but I do see the utility of it.
What had me stumped for almost an hour though was why it was giving me such high seismic shear loads. Then I went back through the settings and realized it had my Response Modification Factor set at "2" because of the gypsum on the other side of the ext. shear walls. Once I set this to 6.5 everything was it should have been and my seismic loads made sense.
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
To envelope the design as much as possible I will spec. out the sheathing and holdowns with the worst load case from either the rigid or flexible analysis. This may be overly conservative but I want to try and pick up as much load from the wall of windows as is reasonably possible.
The one other annoying thing about Woodworks that I noticed that I thought might be worth mentioning is that along any given wall line it only allows one type of shearwall to be specified or one type of non-shear wall. It does not seem possible to have two different non-shear wall panels with different sheathing specifications. I don't know if it changes the output significantly or not but on some wall lines I have walls that are exterior and some that are interior (both non-shear). You wondering in anyone else has noticed this and how they have dealt with it.
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
http://design.medeek.com/resources/footing/2014-02...
Which gives me an 8" x 24" stemwall, with a 22" x 12" footing. The stemwall width and footing depth and width are governed by the requirements of the Simpson SWSB. The footing requires two longitudinal #5 bars for shrinkage and temp, no transverse reinf. required. The stemwall, due to the high uplift of the shearwall requires (2) #5 bars at the top and (2) #4 bars at the bottom, with vertical bars in the high shear areas for shear reinforcment (#4 bars vert. @ 12" o/c).
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
I have also not determined the best way to deal with contributions from adjacent walls to help counteract the overturning of a footing under a shearwall. The latest residence was able to work out mostly but when I ran the numbers on the interior shearwall at the closet (8.4 feet in length) it did not work out for either overturning or sliding. The only way to make it work in this respect was to assume that the foundation walls and footings it connected to provided enough additional resistance to counteract the high lateral loads. The shearwalls tributary dead loads were not enough. However, how much does one assign from the other connected walls to provide this additional overturning resistance?
A confused student is a good student.
RE: Wood Shear Wall Software or Spreadsheets
You can take as much tie down resistance from perpendicular walls as you need so long as equilibrium is satisfied and there's a capable load path available for the tie down force to develop. Foundations can be a bit nebulous in that there's a lot of continuity and it's tough to know exactly what load goes where.
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: Wood Shear Wall Software or Spreadsheets
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: Wood Shear Wall Software or Spreadsheets
The worst part is this exact design has been built by him at least 4 other times (prior to any engineering being required by the jurisdiction and an inspector that actually checked the plans) so my calling out shearwalls and special hardware all over the place appears like serious overkill to him.
I think part of the problem here is that most of the contractors are used to building whatever and however they want and I am fighting that right now. So now I've gained the reputation,"His prices are reasonable but construction costs of his engineered designs are high."
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Wood Shear Wall Software or Spreadsheets
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: Wood Shear Wall Software or Spreadsheets
Most carpenters (and more specifically residential framers) think anything more than commodity lumber, plywood and a nail-gun is overkill. Once you start making them block shear walls and provide proper connectors and tie downs etc. they call it overkill.
You need to find a happy medium, wood is fairly proficient at load sharing (even if you can't adequately analyze it). One thing I have noted, when you need a hefty simpson product, sometimes it's cheaper to just custom fab a steel plate connector to fit the purpose. A lot of the contractors have a buddy with a steel shop (at least in my experience).
I also in these type of scenarios (tall walls of windows) talk to the contractor the first day about that specific wall. Including describing to him an overkill preliminary framing for the wall and then talk to him about the option of looking into steel framing. That way when the design in finalized he had his say on day 1 and can't grumble about the outcome at the end.
RE: Wood Shear Wall Software or Spreadsheets
Ultimately, you will have to turn this around and make your prices higher, but the cost of construction easy and cheap.
The more experienced you get, the more it will go this way.
RE: Wood Shear Wall Software or Spreadsheets
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: Wood Shear Wall Software or Spreadsheets
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
RE: Wood Shear Wall Software or Spreadsheets
"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."
RE: Wood Shear Wall Software or Spreadsheets
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
RE: Wood Shear Wall Software or Spreadsheets
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: Wood Shear Wall Software or Spreadsheets
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
www.medeek.com
RE: Wood Shear Wall Software or Spreadsheets
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.
RE: Wood Shear Wall Software or Spreadsheets
This should be your new sig!
RE: Wood Shear Wall Software or Spreadsheets
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.