New rafter calc, kick the tires

[Don P]

OK, another try. I think I am beginning understand making an array of data and then parsing it to use in calculations. My array lists each species and grade, and stores the Fb, E and Shear of each. When you select a species and grade the calculator then pulls out the design values that go with that selection. I think I understand your warning Raphael, my count for pulling that data out starts at 0 (Fb=0, E=1, Fv=2). All I can say is I think its working on my machine. I've just put a few species and grades in so far. Let me know if this is looking easier to use. Holler if it puts out trash too  Do y'all think the design values should be listed in the output?
https://forestryforum.com/members/donp/beamclc06b.htm

[Raphael]

I'd like to see the design values, but they aren't really needed for the intended purpose .

I haven't seen any anomolies running the calculator with Opera 8.54 but I do have an interesting one with Opera 3.61
It looks like 3.61 is expecting a numerical result in the pass/fail field so it's reporting 0 (zero).

[Jim_Rogers]

I'd like to see the design values also.
It's nice to see them just to make sure they are correct, and what they actually are....

But the pull down selection will be a great feature to make it faster and easier.....

Thanks DonP.....


Jim Rogers

[Max sawdust]

Don P,
When you get a chance can you add Northern Red Oak to the pull down list. 
THanks
Max

[Don P]

Click that last...06b link above again, I think I've got about half the species in the table listed so far.
The design values come up when you hit the "show result" key...still need to work on that part some I think.

I realized I've got enough info to add a calc in there to give minimum bearing square inches at each end of the beam, that might be a good thing  ???.

[Max sawdust]

Thanks Don!
max

[Don P]

The rafter thrust calc I posted earlier might come in handy occasionaly.
Rafter Thrust and Tension

Ignore the nails and look at the thrusts if doing TF. Those thrust loads are what your joinery is trying to resist. I put in nails and 2x lumber as that is my most common size and connection. That can be figured for bolts, wood dowels or any other connection.

I had a discussion with a framing carpenter on another forum, here's part of that post describing the longhand for thrust;

Here's how to figure the thrust.
Thrust =wS{1-cos^2(theta)/2}/sin(theta)
w= total load on rafter per lineal inch
S=span in inches
theta= angle between rafter and horizontal

Assume 6/12, framed on 24" centers, let's give it 40 psf total load.
w=40*(24"/12)/12=6.66pli ...40psf * 2 square feet/12" per lineal foot=6.66pounds per lineal inch on the rafter
Thrust=6.66 * 96(1-(.89415 squared)/2)/.4477 = ~860 lbs thrust at the cj/rafter connection.

[Max sawdust]

DonP,
Thanks
Are you going to put the new simple beam calculator we have been playing with on this thread in the forum extras tool box?
Much quicker with the drop down menu when complete..
Thanks again for the nice tools.
max

[Don P]

I think I got it.
This index page should  be working and linked over in the toolbox;
https://forestryforum.com/members/donp/beamindex.htm
I kept both versions of the simple beam calc.
I got hired as a consultant today to help with the restoration/remodel of our oldest local inn and house of dubious distinction.  Its log and timberframe. I wanted to check some joists that weren't on the drop down calc, so I looked it up and used the old one. (they won't break but they're out there) I think we'll run into that fairly often. Use the quick calc when you can and the old one when you gotta.

[Don P]

I took Rapael's suggestion and worked a set of sample checks in the text part of this calc to determine browser compatability;

https://forestryforum.com/members/donp/beamclc06b.htm

Please let me know if it doesn't work right for anybody.

Remember this calc is for heavy timber (5x5 and larger) it will be very conservative with dimensional lumber.

[jpgreen]

Guess what Don...

I ran your compatability test and it passed on the first numbers, and then kept on passing with the new numbers...  ;D

Definitely won't work with my computer or browser..  :D

That's what was confusing the heek out of me before..  : ;D

[Don P]

DanG!
Seems like its just grabbing the "Pass" and running with it. Are the output numbers failing and its just saying pass or is it deeper? I'm listening if anyone's got ideas for a check  :-\.

[Jim_Rogers]

Don:
I'm using Mozilla Firefox and it ran correctly with all the tests....
Jim

[Raphael]

  Works here under windoze 98se with MSIE 5.0, Opera 8.54, and Firefox.  I also get the proper mathmatical results with Opera 3.61 but the interpretation is always 0 (zero).
  I'd like to know what jpgreen is getting for mathmatical results and what values his browser is getting from the species pull down box for Douglas Fir #2 B+S...  I'm getting fb=825,  moe=1 (million), and fv=165.  If it's an offset in the pulldown box then he might be getting the values for either #1 Doug Fir B+S or SS Doug Fir P+T both of which are strong enough to pass where #2 fails.

[jpgreen]

I'll recheck, and use different browsers when I get a chance.

I just found out this morning our county changed my parcel snow load to 100lbs from 80.

I'm in a serious bind now with my 4x6's... 24 O.C.  at 16' span. We calculated that I would have to install a 6x14 supporting beam to cut the span in half with an additional post and footer.

Now I don't know what I'm going to do.  I wonder if I can run the 4x6's on 16" centers and get there? Old man winter is closing in, and it doesn't look good for me...   :

[Jim_Rogers]

You can always add rafters and reduce the load per rafter, that will work if you have already milled your rafters.
But the point that farmer77 made about all that roof load being held up by the center bent is very important, and those pieces will have to be reviewed if you haven't done that already.

Jim Rogers

[Raphael]

  That's some serious snow load!  The numbers are beginning to look like those I'm seeing for a sod roof... 16" OC w/ an 8ft. (7.5ft. clear) span with a heavy dead load value of 20psf, looks good from here.  I've forgotten you're roof's width but up to 22" OC passes so if 19.2" (multiples of 8ft.) or some other value up to 22" fits the roof you can save a couple of rafters.

We calculated that I would have to install a 6x14 supporting beam to cut the span in half with an additional post and footer.

That "additional post" is a mid-span support?
Like Jim says with the additional 20lbs of snow load you may find that beam needs resizing or a pair of posts.

[jpgreen]

Thanks Jim, and Raphael                                                                 .

I milled all the 4x6's already, and I have enough to sqeak by with 16" OC, but I'll be short 6- 8' 4x6's for the gable section now. THe shed section is 16' x 26', and I have not milled up the mid-span cross supporting beam that will cut the 16' span in half, so we can recalculate that.

[Don P]

I'm working out ok with 6x12's for the shed center beam in #2 Dougfir B+S and 2 midposts (a 6x10.5 actually worked for me). One post was not looking too good, the single post was getting into buckling trouble at about 8' tall, with 2 I think you're good to about 10'6". More reasons to take up farmer77 on that offer, you all have winter loads in a serious way  .
I entered 6933 lbs Total (800lbs per foot on the beam x 8.66' span)
1040 Dead
104 Span
6 wide
12 deep

Output;
Section Modulus Required 109.24
Section Modulus Input 144

Deflection .100"
Max Roof Allowed .433"

Shear
Section Required 31.51
Section Input 72

JP, try running those input numbers and seeing if those important outputs match. Sorry for the trouble... and for dragging the thread all over creation  :. I'm hoping its just in the Pass/Fail part of the program.

[jpgreen]

Hey thanks for the help Don.  You guys are awesome. I'm new to this stuff, and it's great to know someone's got your back when in panic mode..  :D

Chris- (Farmer77) has graciously helped me with this. The guy is REAL busy.  Just has the little job of engineering the whole highway system for the northern state of California, and more..   (no exaggeration factor :D) ...... ;D

He fires off terminology and calcs that make my head spin for awhile..  :D

Soon as I get some time, I'm going to re-run the numbers and analize my whole project with your calculators so I can get a better grip on this engineering.  Right now Chris's got my brain tied up..  :D ;D :D

[jpgreen]

I've got a question...

What's the best for 6x6 posts, for structural... Boxed heart from 12-15" logs, or parts of a heart from a 30" diameter log?

It's all Doug Fir, and few tiney knots. I'm trying to decide which to use on my mid wall of the  building that holds the most weight.. 

[Raphael]

Boxed heart especially when it's green timbers.
  If you've got something large enough to mill it FOHC it could be used but the cross section tends to dry to a diamond shape.  If you leave heartwood on one corner of a green timber you run the risk of it checking all the way through and it will tend to dry into a big banana.

[Don P]

There's no 6x6 like an 8x8  ;D.

I'd agree to box it. A column must stay straight. If a heavily loaded column begins to bow it loses capacity and bows more, losing capacity, it bows more. That process of "creep deflection" ends at ground level, very bad.

FOHC has the greatest chance of producing high grade, check free or smaller checked timbers. It also has the greatest chance of producing bowed timbers. Keep an eye on slope of grain when resawing bowed timbers straight.

[jpgreen]

Cut and installed all the posts today.  I put the boxed timbers on the heaviest loaded wall.  If the other ones twist or bow, they are easy to acess, and easily replaced.

14' at the top of the plate gives you a nose bleed..  :D