Author Topic: Truss Calculators  (Read 375646 times)

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Offline Medeek

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Re: Truss Calculators
« Reply #375 on: March 28, 2016, 07:36:23 PM »
Version 1.4.7 - 03.28.2016
- Added Cathedral truss type, configurations: (4/X, 6/X).
- Metric input enabled for cathedral truss type.
- Added gable end trusses for cathedral truss type.



Note, that not all configurations have webs enabled however the top chords, bottom chords, gable end trusses and all advanced options are enabled.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

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Re: Truss Calculators
« Reply #376 on: March 29, 2016, 07:39:46 AM »
Just as a word of warning this plugin is far from a polished or finished product.  There are still a lot of loose ends that need tying up.  Case in point I have not yet enabled gable end trusses for the attic truss type.  The reason is the complication of dropping the top chord for structural outlookers where the attic truss has a spliced top chord.  Below is an example of a attic truss with a dropped top chord that I have encountered in the past but I don't know if this is the best method of handling this situation. 



I would like to enable structural outlookers for attic trusses in the next few days just to wrap this up.  Any thoughts or suggestions or examples of similar configurations are very much appreciated.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer


Offline Medeek

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Re: Truss Calculators
« Reply #377 on: March 29, 2016, 09:16:51 PM »
To further clarify the framing details with regards to attic trusses and structural outlookers I've created a sample model with a proposed dropped top chord gable end attic truss:



Please download and review the model here:

https://3dwarehouse.sketchup.com/model.html?id=u8c3afc5c-482a-41ea-b223-988b1cccd8bc

I've also included the infill wall framing to help put everything into reference (light green).

Is this the appropriate way to frame an attic truss (gable end) with structural outlookers?
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

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Re: Truss Calculators
« Reply #378 on: March 30, 2016, 06:25:17 AM »
The reason I provide the full attic opening at the gable end truss is so that the framed in wall can be the nominal ext. wall thickness of 5.5 inches and allow for R-21 insulation.  I've had some truss plants provide the typical vert. webs for nailing off the sheathing over this space but then one has to fir it all out anyways to get the appropriate wall thickness for the insulation.

If the wall below the gable end truss is sufficient for bearing then the gable end truss really does not need to have any structural capability so all of the diagonal webs can go away.  One could also  get away with a 2x4 dropped top chord with the stacked top chord at the eaves as shown.  It would make sense to have the same depth at the bottom chord though so that the floor sheathing has a convenient nailing surface right to the edge of the building.

Alternatively one could do away with the gable end truss entirely and just balloon frame the wall from the ground floor up or from the attic floor up.

The question is which method should be employed within the plugin.  I would prefer to use the most commonly employed solution.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Don_P

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Re: Truss Calculators
« Reply #379 on: March 30, 2016, 03:42:38 PM »
A pic is eluding me, reply #376 looks very familiar. Right down to the stair in that end. I'm about certain the bracing level under the piggyback is the same elevation from common to dropped gable. Yes leave the room area "hollow" to be field framed.

We set one of your designs last weekend. I ran the persnickety truck and got to watch a 70 year old pup do my job, and do it well :)


Offline Medeek

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Re: Truss Calculators
« Reply #380 on: March 30, 2016, 07:24:00 PM »
Any pictures from this recent build?
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

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Re: Truss Calculators
« Reply #381 on: March 30, 2016, 10:28:11 PM »
Six possible end details for a flat truss (Pratt 4 panels), there are probably others but these seem to be the most common:



1.) Mansard w/ Parapet
2.) Parapet
3.) Mansard
4.) Overhang
5.) Cantilever
6.) None

Both Mansard configurations can also have an optional overhang as shown.  The Parapet configuration should allow for customizing the thickness of the parapet wall.

View model here:

https://3dwarehouse.sketchup.com/model.html?id=ude4e9b15-f67e-40de-a99f-97d2044182ad

This truss type with its many end configurations would work well with an HTML UI, that is the direction I will be going with future user inputs and interfaces since the ability to customize is unlimited.

With the flat trusses I will initially offer both Howe and Pratt with the ability to utilize a low slope or zero slope.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

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Re: Truss Calculators
« Reply #382 on: April 01, 2016, 08:20:54 AM »
Version 1.4.8 - 04.01.2016
- Added Mod Fan common truss type.
- Structural outlookers (vert. & horz.) enabled under advanced roof options for Common (Mod Fan) truss type.



View model here:

https://3dwarehouse.sketchup.com/model.html?id=u3cf3d051-4d02-4490-af81-5693296cca33

With the addition of the Mod Fan (Triple Fan) the line up of common trusses is complete.  I still need to add in raised heels and structural outlookers for some of the configurations. 

Theoretically I could add in additional configurations of the Fink and Howe truss types for extremely large roofs but the largest I've ever seen is a raised heel Quad Fink (10/9).  Large spans beyond 70'-80' are probably not practical as far as a single span common truss roof.  At that point you pretty much go with large flat roofs with interior columns and girders and all steel construction (think Walmart or Cosco).
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

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Re: Truss Calculators
« Reply #383 on: April 02, 2016, 10:16:26 PM »
Tray truss algorithm:



A more complex algorithm would be required for a non-centered tray.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer


Offline Medeek

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Re: Truss Calculators
« Reply #384 on: April 03, 2016, 10:59:28 PM »
Tray Trusses working now I just need to enable gable ends and advanced options:



Note the three large trusses are all 36' span with different tray widths and different web triangulations.

View model here:

https://3dwarehouse.sketchup.com/model.html?id=ub0bbdf3a-4749-4e8a-8016-758869f692b6
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Don_P

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Re: Truss Calculators
« Reply #385 on: April 04, 2016, 03:32:20 AM »
I'm confused. Can you explain the non viable configurations in the sketch above, I'm not understanding what is kicking them out or the difference in them and todays sketches  d*

Umm, I haven't taken pics of the shop trusses we've been raising... and not sure I'd feel comfortable posting them. The learning curve was steep and so I will pass the info part on. Basically when site building trusses they all have to be identical. The truss needs to be lofted out on the assembly surface and better yet, lofted and then blocks set to create a jig. Things went pretty well until we got down in the stack. We set the first several that were built using a tape and eyeball and have problems, the bottom chord was not kept straight and when the webs are installed it locks the truss in either a humped or hogged height. By the end of the day I had cut the webs out of what was the original truss and gotten it to settle some, the peak and heel gussets are still relatively fixed and the surrounding trusses are not planning correctly either. Plan B; We'll install 2x4's dangling vertically from the peak gusset, nailed flatways onto the gusset very well. Then run a 2x12 ridge under the peak gussets and draw the gussets to the 2x12 with bar clamps and attach that together well. I expect to cut out and replace several more webs if the trusses need to move much. If the peaks and heels remain fixed we'll need to remove and replace those very well nailed gussets.
So, lessons learned, build very carefully on a full scale set of lines at the minimum. It wouldn't hurt to stack the trusses in their final orientation on the ground as you build them and make sure they line up with one another perfectly.
« Last Edit: April 04, 2016, 03:54:26 AM by Don_P »

Offline Medeek

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Re: Truss Calculators
« Reply #386 on: April 04, 2016, 05:35:08 AM »
Technically the non-viable configurations are okay but I am assuming that the top chord loads will be larger than the bottom chord loads and with that I am applying a rule of a 6' max. on the top chord panel length and a 9' max. on the bottom chord panel length.  The viable options approximate this ratio better than the non-viable options.  If one of these trusses were somehow a girder truss that would all change of course.

My biggest concern with site built trusses is quality control and of course proper jigging so they all come out identical or nearly so.  The truss plants have some very expensive jigging systems and near perfect assembly conditions to help with this but even so I've seen some very sloppy work come out of some of these plants with respect to misplaced plates and even plates entirely missing.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

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Re: Truss Calculators
« Reply #387 on: April 04, 2016, 08:29:48 PM »
Version 1.4.9 - 04.04.2016
- Added Tray truss type, configurations: (AUTO).
- Metric input enabled for tray truss type.
- Added gable end trusses for tray truss type.

A few more configurations:



The next truss type I would like to add is the coffer truss but I don't have a lot of good examples of this truss type to study.
« Last Edit: April 04, 2016, 09:14:25 PM by Medeek »
Nathaniel P. Wilkerson, P.E.
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Offline Medeek

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Re: Truss Calculators
« Reply #388 on: April 11, 2016, 06:21:28 AM »
Version 1.5.0 - 04.11.2016
- Added Mono Scissor truss type, configurations: (2/2, 3/3).
- Metric input enabled for mono scissor truss type.
- Added gable end trusses for mono scissor truss type.
- Structural outlookers (vert. & horz.) enabled under advanced roof options for Mono Scissor (2/2, 3/3) truss types.



When the raised heel option is selected the pitch of the bottom chord may equal the top chord creating a half vaulted parallel chord truss.

View model here:

https://3dwarehouse.sketchup.com/model.html?id=8e90b148-e241-4c88-b8b4-83c21ec12a3d
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer


Offline Medeek

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Re: Truss Calculators
« Reply #389 on: April 13, 2016, 09:07:17 PM »
Updating the hip roof module so that an appropriate wireframe is displayed while using the roof positioning tool:



I will roll a revision once I've finished updating all of the rafter roof types with updated wireframes (preview graphics).
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

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Re: Truss Calculators
« Reply #390 on: April 16, 2016, 10:20:42 PM »
Version 1.5.1 - 04.16.2016
- Added Dutch Gable Rafter Roof (all advanced options enabled).
- Added wireframe (temporary) graphics to the roof positioning tool for rafter roofs.



View model here:

https://3dwarehouse.sketchup.com/model.html?id=614d542d-8dcc-4f2f-bbdc-fd4bc4c1f1e7

I still need to setup ceiling joists for hip and dutch gable roofs.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

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Complex Roof Framing - Nested Dutch Gable Roof
« Reply #391 on: April 17, 2016, 11:01:15 AM »
A nested dutch gable roof created with the plugin.  The roof is initially generated by creating three dutch gable primitives and then deleting and trimming certain elements.  The most time consuming is the creation of the two valley rafters.  I think it might be helpful to have some sort of valley rafter tool if I can figure out a good way of doing that.



View model here:

https://3dwarehouse.sketchup.com/model.html?id=2676e970-a79e-40a3-8c77-63208c9d93ef
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Don_P

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Re: Truss Calculators
« Reply #392 on: April 17, 2016, 05:01:49 PM »
Wow, that's kind of cool, not a roof I'd have ever thought of. If I select 2 points and click valley can it justify and insert... just rambling beyond my ken.

This is a framing detail shot of some hip framing from last week.

 The porch roof is 3/12 on both sides of the hip, I used 2x8 rafters and double 2x12 hip. The hip birdsmouth was not going to land over support. You can see from the intersection with the dragon piece that the level seat cut would have extended about that far out from the support. That is one way out of the problem. I've picked up double hangers for the hip to dragon.

The design calls for a 3 post corner. The one for the left of the corner was too twisted so it isn't in yet. A slot in each end allows the post to slide in over the steel plate that is bolted into the built up triple 2x8 porch carry beam and extending down into the post. Two steel pins in plugged holes will attach the plate to post top and bottom.

Offline Medeek

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Re: Truss Calculators
« Reply #393 on: April 17, 2016, 07:54:12 PM »
I like your use of the double hip, are you ripping a bevel into them or dropping them?

With that low of a pitch the birdsmouth starts to cause problems, this method seems like a clever way to handle it, I've never heard of the term "dragon" before, where else is this used?

Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

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Re: Truss Calculators
« Reply #394 on: April 17, 2016, 07:57:23 PM »
Looking at the half hip roof next.  Fairly cut and dried but I'm a little undecided how to handle the birdsmouth cut of the hip rafter where it intersects the discontinuity of the gable wall.  I will probably use the same birdsmouth cut on the half hip rafters as the other common rafters of the roof, but this could be different if one wanted to frame it that way and the gable wall would just raise slightly.  I've never had much respect for framers or carpenters until now (my bad) but after spending some time working through some of these bizarre roof types my level of respect has changed.



View model here:

https://3dwarehouse.sketchup.com/model.html?id=ce1dd25e-7674-4625-981e-52a4e07b9997
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer


Offline Don_P

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Re: Truss Calculators
« Reply #395 on: April 18, 2016, 02:24:57 AM »
Here's some of the history of the term, this is probably correctly a diagonal beam... I'm guessing "dragon" in either diagonal orientation probably devolved from that.
http://www.mileslewis.net/lectures/04-history-of-building/puncheons-and-dragons.pdf

I prefer to back rather than drop if possible, and with a double hip or valley backing exterior and/or interior it's easy. the double makes working around the corner easier too. This took a 10 degree backing angle, or it would have been ~1/4" drop, so not much either way.

This was a wrap around porch, on the first hip the jacks "shake hands" across the hip, I already had the cjs in before thinking to take a pic and its kind of busy, as I made it around to this one, since the rafter spacing was set and coming across the back of the house was set by the house framing, they do not line up. Not a bniggie but another reason I like the double hip or valley. I read it sort of like a single top plate vs a double top plate... if things don't line up using a double helps hold the framing in line until its all sheathed.

This last hip to me is a jerkinhead or clipped gable.

Been there enough, carpentry's just a handful of nails and we bang and bang until its done  ;D One old timer said roofs and stairs separate the men from the boys real fast.

Offline Medeek

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Re: Truss Calculators
« Reply #396 on: April 18, 2016, 11:18:45 AM »
Per user request:

Version 1.5.2 - 04.18.2016
- Added energy/raised heels for small span attic trusses (less than 24 ft.), 1 variant: vertical w/ strut.
- Added some additional logic to improve the triangulation of the upper attic of attic trusses.



When I get some more time I will add in slider and wedge raised heel options for the attic truss type but at that moment it is low priority since most users seem to favor a fairly tall raised heel when utilizing it with attic trusses.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

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Re: Truss Calculators
« Reply #397 on: April 20, 2016, 10:53:03 PM »
Version 1.5.3 - 04.20.2016
- Added Mono Cathedral truss type, configurations: (2/2, 4/4).
- Metric input enabled for mono cathedral truss type.
- Added gable end trusses for mono cathedral truss type.
- Structural outlookers (vert. & horz.) enabled under advanced roof options for Mono Cathedral (2/2, 4/4) truss types.
- Added Mono Scissor truss type, configuration: (4/4).



View model here:

https://3dwarehouse.sketchup.com/model.html?id=2ba29c11-a7b2-4913-a758-c005eb1288f9

I manually modeled this truss type about two months ago and I have been meaning to add it in, finally got it done tonight.

Manually created model here:

https://3dwarehouse.sketchup.com/model.html?id=u5c030ac2-f2e4-4c8d-8d9b-67bfa780ee7f
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Don_P

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Re: Truss Calculators
« Reply #398 on: April 21, 2016, 04:03:51 AM »
Oh, came across another name for what I called a jerkinhead gable... "snug dutch"

Offline Medeek

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Re: Truss Calculators
« Reply #399 on: April 21, 2016, 05:22:59 AM »
It seems there I quite a few different terms for this roof configuration: half hip, jerkin head gable, clipped gable and now snug dutch. 
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer