|
| Author |
Message |
MJW
Member
|
# Posted: 2 Feb 2013 07:55pm
Reply
We are building using beams made with 3 - 2 x 12 attached to 6 x 6 posts.
There seem to be many choices of fasteners to attach the beams to the posts.
Can anyone offer share their experiences on what they used and any recommendations they have based on their experience?
Thanks!
|
|
Anonymous
|
# Posted: 3 Feb 2013 12:25am
Reply
I would add a piece of 1x6 to each side of the beam where it crosses the post, approx 1foot long then use 2 "T" brackets found at hardware sore or manufactured from 2 pieces of flat bar Wilde to "T" and drilled for galvanized nails. That way the bem remains cantered over the post and secured from movement. This is supposing hat he 6x6 ar full dimension and he 2 x 12 are 1.5 inches in thickness
|
|
Gold winger
|
# Posted: 3 Feb 2013 12:32am
Reply
If 2x12 are full dimension then omit the 1x6 pads and still use "t" brackets. If any framing is treated then make sure you use brackets suitable for treated lumber
|
|
MJW
Member
|
# Posted: 3 Feb 2013 09:17am
Reply
You guys mean these things?
|
|
fpw
Member
|
# Posted: 3 Feb 2013 11:20am
Reply
I would would also secure with timber screws (10 or 12 inch) and nail in some knee braces which will help prevent the structure from racking in the wind.
|
|
Gold winger
|
# Posted: 3 Feb 2013 07:08pm
Reply
MJW yes those are the right things. Knee braces are correct if the beam is all exposed. If it is part of wall construction then the wall does the bracing. If you are trying for the exposed beam look and you don't want the brackets, knee brace that are let into the supports are the way to go.
|
|
Borrego
Member
|
# Posted: 3 Feb 2013 11:45pm
Reply
These are much stronger if you need the strength...
|
|
MJW
Member
|
# Posted: 4 Feb 2013 08:35am
Reply
Quoting: Borrego These are much stronger if you need the strength...
They look to be.
What are they called? I didn't see these at Lowe's when I was looking.
|
|
|
bobbotron
Member
|
# Posted: 4 Feb 2013 12:28pm
Reply
I guess the main thing is, I don't think you can't really rely on any of these connectors for shear strength. A knee brace is the way to go for that as others have said.
What are you building?
|
|
bldginsp
|
# Posted: 4 Feb 2013 04:00pm
Reply
When you ask the question- 'what is the best connector' you are essentially asking an engineering question. The proper connector for a given joint is a function of the kinds of forces applied to the joint, and the strength of those forces. These things vary a great deal in different building designs. You can't really answer the question without doing a thorough engineering analysis of the entire structure.
That said, if you know or expect that the only forces on the joint will be downward forces, not uplift forces from earthquakes or knee braces, no shear forces from lateral movement, then all you have to do is keep the beam on the post. That is simply done by pretty much any method, and common sense should dictate the effectiveness of your method. But common sense cannot dictate engineered calculations, so if you suspect that your particular design will introduce other forces to the joint, there is no other way to accurately determine an effective solution than to get an engineer.
An experienced engineer should be able to look at your plans and tell you off hand whether or not you have designed post/beam joints that are other than simple down bearing. If not, it's easy. If you have, that's another ball of wax. With any post and beam structure I'd at the very least have an engineer give it a quick look over, if not a thorough engineered design. They'll tell you if you have designed yourself into a corner, or designed an unsafe design. Might save your life by preventing two tons of snow crushing your roof onto your head while you sleep.
|
|
Borrego
Member
|
# Posted: 4 Feb 2013 09:42pm
Reply
Quoting: MJW What are they called? I didn't see these at Lowe's when I was looking
They are made by Simpson. Those are ECCQs, I think.. an engineer is a good idea if you have any doubts as bldginsp notes....some people are experienced enough to look at a simple structure and figure it out well enough. We've been doing this for a few centuries 
|
|
bldginsp
|
# Posted: 6 Feb 2013 01:41pm
Reply
Borrego- he said he's using post and beam construction, which typically uses braces to provide lateral support. When a braced post and beam frame moves laterally, the brace forces the beam up off the post. When this happens, all lateral strength is gone and collapse can occur.
You're right that with a simple stucture that only has down bearing forces it's pretty easy to pick a workable connector solution. We have been doing this for hundreds of years, but hundreds of years ago the timber framers used large tenons to join beams to posts, partly to deal with this uplift issue. If you aren't using such tenons, and are relying on connectors with braces, your connector must account for the uplift. That's not easy to eyeball.
A stick framed structure with plywood braced walls does not have this issue at all. One more reason that simple stick framing is easier to design and execute.
|
|
MtnDon
Member
|
# Posted: 6 Feb 2013 03:01pm - Edited by: MtnDon
Reply
All buildings have lateral forces acting on them at some point in time. If the wind blows you have lateral forces. Those can add up tp numbers greater than one might think.
Our mountain location receives storm gusts in the 55 to 60 mph range a few times a year. If I use 60 mph on a building with a roof ridge height of about 15 feet that wind speed will generate approximately 7.3 pounds per square foot. Make that long cabin wall 30 feet long and that equals 450 sq ft and a total lateral force of 3285 lbs.
Code calls for planning for a 90 mph three second gust minimum everywhere in the country; some places higher.
Using 90 mph I get 16.5 PSF, = 7425 pounds total force.
Now that is a simple approach and does not take into account what else is going on. Wind on the long side like that will also be creating a lift on the near side foundation and a downward force on the farside. It wall also be trying to "rack" the ends walls, trying to deform the square or rectangle.
That is why it is important to include sufficient sections of brace walls in a structure. We had mention of that in a cabin a short time ago, a cabin with a door and a lot of windows in the end wall. The calculations can get complicated in a hurry. Therein lies the beauty of a building code like the IRC; it is a prescription, which when followed avoids the need for consultations with paid engineers.
One thing not mentioned for connecting is the use of plywood plates, most likely 3/4 inch PT ply. After we built our cabin I ended up talking with engineers I met. One of the additions we made to the pier/beam foundation was to cut plywood plates and nail them over the pier to beam connection; 8D ring shank nails every 4 inches over the areas that contacted the pier or the beam. Plates were approx. 24 x 16 inches with non nailed corners trimmed off a little at 45 degree angles. Sorry, no pictures.
The other thing we did was to build a shear wall across each end between the piers. PT 2x's and 3/4 plywood. Then the same thing again from each corner oier down the log sides to the next post in line. In retrospect it would have been better to have built a better foundation in the first place.
Live 'n' learn.
|
|
241comp
Member
|
# Posted: 7 Feb 2013 12:50pm - Edited by: 241comp
Reply
My cabin is built using 3-ply 2x12 beams on top of 6x6 posts, same as you are doing. I used Simpson BC6Z post caps which have a lateral load rating of 2000lbs and uplift rating of 1050lbs. The "Z" in that part number stands for zmax which is Simpson's hot-dipped galvanized coating with three times the zinc per square foot of standard galvanized (G185 vs G60). I chose to go with zmax (vs standard galvanized) because I wouldn't want to have to replace one of these post caps (with the cabin sitting on it!) and the price difference was negligible. In fact, I went with zmax for all of my brackets for this reason.
You can get them from Amazon or any of a number of other online suppliers. I believe Lowes can special order them.
You can see what these look like installed here: 
|
|
Bldginsp
|
# Posted: 7 Feb 2013 01:13pm
Reply
You always want to use Z max or other hot dipped galvanized metal when in contact with PT. The current formulations of preservative are corrosive to iron, particularly where there will be moisture contact. Good choice. No, I don't have stock in Simpson.....
|
|
Bldginsp
|
# Posted: 7 Feb 2013 02:03pm
Reply
But I should say that I cannot speak for the engineering value of the connectors you are using. Whether or not they are adequate can only be determined with a thorough engineering analysis of the building and loads it will take.
|
|
MJW
Member
|
# Posted: 7 Feb 2013 07:35pm
Reply
Thanks 241comp. This is exactly the information I was looking for.
|
|
|
