Author Topic: Truss Calculators  (Read 375645 times)

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Offline Medeek

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Re: Truss Calculators
« Reply #325 on: March 04, 2016, 07:27:39 PM »
How about this truss type?

Version 1.3.5 - 03.04.2016
Added Bow Barrel truss type, configurations: (8/8).
Metric input enabled for bow barrel truss type.
Corrected a bug with the webs of the bowstring truss type.



View model here:

https://3dwarehouse.sketchup.com/model.html?id=u754b5fc3-c3ea-48cb-9f13-24c92ae39d97

Gable end option is also available (not shown in image above for clarity) for this truss type.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

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Re: Truss Calculators
« Reply #326 on: March 05, 2016, 01:19:27 AM »
I find the bow barrel truss very interesting.  Its very similar to a flat truss in a lot of respects but then you essentially create pitch breaks at all the panel points and add some camber to it.



View model here:

https://3dwarehouse.sketchup.com/model.html?id=uf39ab29a-4d1b-458f-b9cb-b1bf882b9774
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer


Offline Medeek

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Re: Truss Calculators
« Reply #327 on: March 05, 2016, 11:39:41 PM »
I'm thinking the next thing I might tackle is an octagonal rafter roof. Something along these lines:



My time allotted to work on the plugin is very limited right now so I'm trying to decide if this would be something of interest for current and potential users of the plugin.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Online Don_P

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Re: Truss Calculators
« Reply #328 on: March 06, 2016, 03:43:58 AM »
The only roofs I've done like that were over bay windows, they are often not a true octagon depending on the width of the center window which may be a wider side with 45 degree wings flanking it.

Offline Medeek

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Re: Truss Calculators
« Reply #329 on: March 06, 2016, 04:12:47 AM »
A couple of other people have commented in a similar manner.  One user would like to see a half octagon.  I can also see where a bay window would utilize this type of roof framing but it might extend over the main roof.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer


Offline Medeek

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Re: Truss Calculators
« Reply #330 on: March 06, 2016, 04:14:14 AM »
Version 1.3.6 - 03.06.2016
- Added Double Howe and Triple Howe common truss types.
- Structural outlookers (vert. & horz.) enabled under advanced roof options for Common (Double & Triple Howe) truss types.



View model here:

https://3dwarehouse.sketchup.com/model.html?id=u456fbc36-6d2e-43ed-af05-5f9ad26f89b4
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

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Re: Truss Calculators
« Reply #331 on: March 06, 2016, 12:42:23 PM »
Nine different truss profiles currently available within the Medeek Truss Plugin:
- Common
- Attic
- Monopitch
- Scissor
- Tail Bearing
- Dual Pitch
- Bowstring
- Bow Barrel
- Floor (System 42)



View model here:

https://3dwarehouse.sketchup.com/model.html?id=ue9b30427-93a7-45c9-abdd-e35b18cac1de

Are there any truss types I am missing that you would like to see added to the plugin?
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

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Re: Truss Calculators
« Reply #332 on: March 06, 2016, 10:33:10 PM »
Version 1.3.7 - 03.06.2016
- Added Soffit Cut within Advanced Options for common fink truss type.



After I'm certain that this feature is robust I will add it to all other truss types and rafter roofs.  For now it only applies to roofs that use a common fink truss (non-raised heel).
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

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Re: Truss Calculators
« Reply #333 on: March 07, 2016, 01:13:33 AM »
Here is one way to frame an octagonal roof.  The basic hip elements were first created with the plugin.  This is a study of this type of roof to see what is required to add it into the plugin:





View model here:

https://3dwarehouse.sketchup.com/model.html?id=u27fa9eb4-683a-4d0e-b77c-17427a401b6b

Another method would be to use an 8 faceted center block.  Dewalt's framing book goes into some alternative methods in some detail.  I prefer the method I have shown above because it is much easier to extrapolate the framing method to include elongated octagonal roofs.  8 common rafters and 8 hip rafters come together at the peak, seems like it would be a real pain to try and fasten these at the peak, perhaps someone could enlighten me on how a carpenter would actually put this together.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer


Offline Medeek

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Re: Truss Calculators
« Reply #334 on: March 07, 2016, 01:42:34 AM »
Nathaniel P. Wilkerson, P.E.
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Online Don_P

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Re: Truss Calculators
« Reply #335 on: March 07, 2016, 04:23:26 AM »
A large post is one way I've seen. Another, I would probably bring in 4 principle hips then header between those as soon as I can get connection room. Set the next 4 hips at correct elevation onto the headers and if needed drop down and header again for the commons.

At some point I'll probably need to do a very steep octagon spire with kickouts at the base to match the 4 Richardsonians on the courthouse in town, those turrets are probably the most common application of a full octagon. I'll try to dig up a shot.

Those hips fail depth of cut.

Online Don_P

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Re: Truss Calculators
« Reply #336 on: March 07, 2016, 04:29:52 PM »
These are the octagon turrets I was thinking of;

The framing in those has held up for over a century... amazingly.

This is a doodle I did awhile back for a gazebo on the lot where the tree is;


Offline Medeek

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Re: Truss Calculators
« Reply #337 on: March 08, 2016, 06:59:32 PM »
Very cool stuff.  Your method of using the header makes good sense.  This aligns with the alternative method described in the Dewalt book I have on framing. 

Here is a similar application with headers for a conical roof:



Searching on the internet found some examples of framing it with all 16 member coming the peak, I guess it is not impossible.



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

Offline Medeek

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Re: Truss Calculators
« Reply #338 on: March 10, 2016, 01:38:17 PM »
Version 1.3.8 - 03.10.2016
- Added wireframe (temporary) graphics to the truss positioning tool.
- Added Boise Cascade BCI® I-joists: 4500, 5000, 6000, 6500, 60, 90.
- Rim joist option enabled for BCI floor joists.
- Removed drop down list for all overhang lengths (truss & rafter roofs). Overhangs are now users inserted values.



The screenshot above shows the wireframe that is displayed for common truss types. 
« Last Edit: March 10, 2016, 09:28:41 PM by Medeek »
Nathaniel P. Wilkerson, P.E.
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Offline Medeek

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Re: Truss Calculators
« Reply #339 on: March 12, 2016, 02:34:42 AM »
This is a study of hip roof framing where unequal pitches meet at the hip (90 deg. to each other). In this case the birdsmouth cut is 3.5" for all jack and common rafters. The hip rafter is dropped and off center so that it lines up with the roof planes.

I assumed that the governing design criteria was that the sub-fascia line up hence the steeper pitch roof has a smaller overhang.



View model here:

https://3dwarehouse.sketchup.com/model.html?id=ue065475f-8b68-4434-a933-776055f50175

I haven't gone through and created the calculations yet for the plugin but the one thing that jumped out at me was the necessity to offset the hip rafter slightly from the hip centerline when a dropped hip rafter is employed.  Please review the model and let me know if there are any problems with the way this comes together.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

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Unequal Pitches Hip Roof Framing
« Reply #340 on: March 12, 2016, 03:13:59 PM »
Another study of hip roof framing where unequal pitches meet at the hip. The birdsmouth cut is 3.5" for all jack and common rafters. The hip rafter is dropped and off center so that it lines up with the roof planes. The hip roof combines a 12:12 pitch with a 6:12 pitch.



View model here:

https://3dwarehouse.sketchup.com/model.html?id=uc12480ec-9330-464b-93eb-56bc73878207
« Last Edit: March 17, 2016, 12:10:04 AM by Medeek »
Nathaniel P. Wilkerson, P.E.
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Online Don_P

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Re: Truss Calculators
« Reply #341 on: March 12, 2016, 06:09:27 PM »
Try keeping the overhang widths equal by allowing the hip to leave the corner.

Offline Medeek

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Re: Truss Calculators
« Reply #342 on: March 12, 2016, 10:18:02 PM »
Never thought of that one.  Another option is to have the same overhang but the fascia don't line up, however that does not seem as common.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

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Re: Truss Calculators
« Reply #343 on: March 14, 2016, 08:37:16 PM »
Version 1.3.9 - 03.14.2016
- Out-to-out span of trusses in the trial version are now limited to a range of: 16 ft. (5m) - 32 ft. (9m).
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

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Re: Truss Calculators
« Reply #344 on: March 15, 2016, 03:58:11 PM »
Version 1.4.0 - 03.15.2016
- Added LP Solidstart® I-joists: 450, 530, 18, 36, 56.
- Rim joist option enabled for LPI floor joists.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer


Offline Medeek

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Re: Truss Calculators
« Reply #345 on: March 16, 2016, 10:20:38 PM »
Version 1.4.1 - 03.16.2016
- Added Soffit Cut within Advanced Options for Gable Roof and Gable Roof w/ GLB.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

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Re: Truss Calculators
« Reply #346 on: March 16, 2016, 11:44:17 PM »
Coming up on the 6 month anniversary of the plugin (April 7).  I'm pretty excited with the amount of work I've been able to do on it.  I would really like to get to some more big items on the list like secondary roofs and dormers but that will take a few days of uninterrupted programming which is really hard to come by at the moment.  Lately, I have been addressing mostly minor items that I can knock out in a a couple of hours.  I usually don't start into a big project unless I think I can complete it in one go since it is really hard to partially complete it and then try to jump back into it at a later date.  The higher the complexity the more this holds true.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

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Re: Truss Calculators
« Reply #347 on: March 18, 2016, 02:36:56 AM »
I've been considering transition trusses and what it might take to add them into the plugin.  Below is a quick study of this type of roof.  I am curious to know if a common trusses is butted up next to a transition truss for sheathing purposes.  Also notice the scissor transition, this situation is a little complicated, not exactly sure how to deal with it.



View model here:

https://3dwarehouse.sketchup.com/model.html?id=ue1772e6a-eb97-4775-b9f8-d12e3e134ba3

For clarity I have removed all of the common trusses in the image below:



One question I don't have an answer for yet is what to do if the gable end needs structural outlookers?  Has anyone ever seen a transition truss with a dropped top chord?

I think it would look something like this:



however I think the framing at the lower peak would be more correct if the top chord members abut like this:

« Last Edit: March 20, 2016, 07:27:45 AM by Medeek »
Nathaniel P. Wilkerson, P.E.
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Offline Medeek

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Unequal Pitches Hip Roof Framing - Revisited
« Reply #348 on: March 18, 2016, 12:40:09 PM »
This is a re-visit of the unequal pitch hip roof a few days back.  Larry Belk, an experienced architect whose advice I highly regard, has suggested that an alternative way to handle this type of roof is to raise the top plate and thereby allow the overhang to remain constant around the roof:



View model here:

https://3dwarehouse.sketchup.com/model.html?id=u24f241c6-d493-45cb-9506-d025d7ebd795

Compare with hip roof 7: 



and model:

https://3dwarehouse.sketchup.com/model.html?id=uc12480ec-9330-464b-93eb-56bc73878207

A few things pop out at me here. 
First the raised top plate method allows the constant overhang with the continuous fascia, overall this is more aesthetically pleasing.
Second the hip rafter is no longer at the corner but is jogged in some amount onto the higher wall.
Third, the higher wall actually is protruding through the sheathing of the lower pitched roof in the model.  Obviously the higher wall needs to be trimmed back some to deal with this.

For the plugin I think I will probably go with option 1 above initially but at some point it would be good to have a checkbox that allows one to choose either of these two options, the code is going to get ugly.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Online Don_P

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Re: Truss Calculators
« Reply #349 on: March 19, 2016, 03:13:42 AM »
Bingo, that's it, often stacking another plate or two and drifting out of the corner will do it. That is where I draw it from the gutter line and work "backwards". Equal overhangs and level fascia is the normal condition, if we do it right they don't see the heartburn  :D.

I'm working on a 3/12 wrap around porch, 2x8's already heavily birdsmouthed due to elevation tightness at the 2nd floor windows. The bird on the 2x12 hips is going to be huge, way too far inboard of the bearing with the heel of that notch... I'll need to land on or at a diagonal beam and then continue on. Hips are interesting.

I've never done transition trusses. I've never seen a scissor gable truss done correctly as yours is, generally they incorrectly have a level bottom. I suspect you need a vertical leg down to the narrower wall and then run up at the smaller scissor pitches, a real sawtooth of a truss, good luck getting good bearing and alignment everywhere in the field though  ??? As for packing a common against a transition, if it is just for a ceiling nailer, let the builder apply a 2x4 to the transition truss when he is detailing out the bracing.