Author Topic: Truss Calculators  (Read 369590 times)

0 Members and 1 Guest are viewing this topic.

Offline Medeek

  • Journeyman
  • *****
  • Posts: 2,063
  • Structural Engineering
    • The Engineering and Design Firm of Medeek
Re: Truss Calculators
« Reply #300 on: February 14, 2016, 05:23:40 AM »
Version 1.3.0 - 02.14.2016
- Added tail bearing truss type, configurations: (Fink).
- Metric input enabled for tail bearing truss type.
- Advanced options enabled for tail bearing truss type.



View model here:

https://3dwarehouse.sketchup.com/model.html?id=u704b9d92-bd38-4895-b71b-19691f31cca7

I have shown 3 configurations of the same roof to display the differences with non-structural vs. structural outlookers (horz. & vert.).  I am not exactly sure how to treat the gable end truss for this truss type since I have never dealt with this type of truss before.  Any sample outputs showing the gable end truss with a dropped top chord for a tail bearing truss would be very helpful.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

  • Journeyman
  • *****
  • Posts: 2,063
  • Structural Engineering
    • The Engineering and Design Firm of Medeek
Re: Truss Calculators
« Reply #301 on: February 14, 2016, 03:02:28 PM »
I am currently investigating the best method to construct the gable end wall and truss with a tail bearing truss.  Show below are 3 different possible configurations:


1.) Structural Outlookers (Vertical)


2.) Non-Structural Outlookers (Horizontal)


3.) Structural Outlookers (Horizontal)

This is just one possible method of framing the gable end wall into the gable truss with a 2x4 outlooker.  Option 3 shown above is somewhat of a question, not sure how that heel joint would come together.

View the model here to analyze the different configurations:

https://3dwarehouse.sketchup.com/model.html?id=u75c42456-c8e5-4002-bc93-779860f8dc61
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer


Offline Don_P

  • Journeyman
  • *****
  • Posts: 4,597
Re: Truss Calculators
« Reply #302 on: February 14, 2016, 05:18:55 PM »
Usually a 3.5" dropped gable truss is standard here, so #1. I've never seen our plants do anything other than spring from plate height no matter what the truss configuration, even a scissor. Part of my complaint with the current engineering handoff point, bracing is up to the engineer of record, generally non existant in residential. I would probably balloon frame that wall and attach a ceiling ledger in practice. That ledger is your effective stud height for lateral. What you have drawn would be difficult to frame and have plane in with the common trusses correctly.

Offline Medeek

  • Journeyman
  • *****
  • Posts: 2,063
  • Structural Engineering
    • The Engineering and Design Firm of Medeek
Re: Truss Calculators
« Reply #303 on: February 14, 2016, 05:58:29 PM »
In a nutshell then your method would be to balloon frame the wall at the gable ends and attach a ledger for the ceiling:



View model here:

https://3dwarehouse.sketchup.com/model.html?id=ub1aa30d4-a7c3-4320-8bc4-03fd128b5913

I agree that a partially sloping wall gets complicated to frame.  From an engineering standpoint the balloon framed wall is the strongest option.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Don_P

  • Journeyman
  • *****
  • Posts: 4,597
Re: Truss Calculators
« Reply #304 on: February 14, 2016, 08:10:58 PM »
Exactly, that's it. I've temporarily slid the truss over, temp screw the top plate to it 3.5" down, build the wall and then slide the truss back and lookout, et.


Offline Medeek

  • Journeyman
  • *****
  • Posts: 2,063
  • Structural Engineering
    • The Engineering and Design Firm of Medeek
Re: Truss Calculators
« Reply #305 on: February 14, 2016, 10:38:23 PM »
So you wouldn't construct the gable wall on the ground then tip it up into place?  I like the idea of using the truss to accurately set your top plate location, that makes a lot of sense.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Don_P

  • Journeyman
  • *****
  • Posts: 4,597
Re: Truss Calculators
« Reply #306 on: February 15, 2016, 03:50:01 AM »
2 things, if I trust the truss to be right on I'll loft the wall on the floor. Second, when a wall gets tall and you only have a couple of people as it goes up it can flip back over you, if in doubt on either of those I'll build it a stick at a time.

Sorry on the KS, there are sure a lot of things I'd like to do if it weren't for the day to day, but the grind keeps me young and handsome  ::)

Offline Medeek

  • Journeyman
  • *****
  • Posts: 2,063
  • Structural Engineering
    • The Engineering and Design Firm of Medeek
Re: Truss Calculators
« Reply #307 on: February 16, 2016, 12:56:23 AM »
Version 1.3.1 - 02.15.2016
- Added Triple Fink and Quad Fink common truss types.
- Structural outlookers (vert. & horz.) enabled under advanced roof options for Common (Triple & Quad Fink) truss types.


Triple Fink @ 70' w/ 2x6 chords
Quad Fink @ 80' w/ 2x6 chords

View model here:

https://3dwarehouse.sketchup.com/model.html?id=u2b57ed6d-9f1f-47c4-9e09-5489940c94b2
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

  • Journeyman
  • *****
  • Posts: 2,063
  • Structural Engineering
    • The Engineering and Design Firm of Medeek
Re: Truss Calculators
« Reply #308 on: February 16, 2016, 03:59:47 AM »
I've been looking at a number of garage designs recently that employ an attic or storage truss.  I'm finding that a lot of them tend to use raised heels to allow for more head room while having a lower roof pitch (ie. 6/12 - 8/12).  I'm thinking about adding in raised heels for the attic truss type in the plugin. 

A quick mock up would look something like this:



View model here:

https://3dwarehouse.sketchup.com/model.html?id=u208d64e3-ddcf-4923-8dfb-d507185fa663

Ignore the unbalance in the panel lengths, in practice and in the plugin they will be properly balanced. 

What I do have a question on is the use of a top chord splice as shown in the above image so that the overhangs do not have to be as deep as the top chord in the non-triangulated region of the truss.  I have never seen a splice used on a attic truss with a raised heel, I don't see why it can't be done but it is always nice to have a confirmation that someone else is doing this sort of thing in practice.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer


Offline Medeek

  • Journeyman
  • *****
  • Posts: 2,063
  • Structural Engineering
    • The Engineering and Design Firm of Medeek
Re: Truss Calculators
« Reply #309 on: February 16, 2016, 11:55:58 PM »
Version 1.3.1 - 02.17.2016
- New submenu item and toolbar icon added for global settings.



I've also addressed a number of bugs for rafter roofs when metric units are being used. I highly recommend everyone download the latest version, especially if you are using metric units.
« Last Edit: February 17, 2016, 03:14:37 AM by Medeek »
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline ChugiakTinkerer

  • Senior Member
  • ****
  • Posts: 630
  • Building a remote cabin in Alaska
Re: Truss Calculators
« Reply #310 on: February 19, 2016, 10:35:51 PM »
Just purchased and installed the plugin.  Man, it rocks!  I'm still designing my 16x28 1.5 story cabin with vaulted ceiling and appreciate the ability to generate and look at different scissor truss options.  Thanks for all the effort you've put into this.
My cabin build thread: Alaskan remote 16x28 1.5 story

Offline Medeek

  • Journeyman
  • *****
  • Posts: 2,063
  • Structural Engineering
    • The Engineering and Design Firm of Medeek
Re: Truss Calculators
« Reply #311 on: February 20, 2016, 10:40:47 AM »
I'm glad to hear that it is being put to use.  Post a picture or two once you've got your geometry where you want it.  I would love to see how it is actually being used.  I've had to take a break for a few days but I will be back to it probably next week and try to add in the raised heel with attic and scissor trusses.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

  • Journeyman
  • *****
  • Posts: 2,063
  • Structural Engineering
    • The Engineering and Design Firm of Medeek
Re: Truss Calculators
« Reply #312 on: February 21, 2016, 01:23:55 AM »
Started to code in the dual pitch truss, the top chords, king post and bottom chord are there just need to add some webs:



Just an FYI, my previous post in Nov. had a sign switched in the last step of the derivation for Span 1, corrected in the plugin to a minus sign and everything is comes out perfect.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline ChugiakTinkerer

  • Senior Member
  • ****
  • Posts: 630
  • Building a remote cabin in Alaska
Re: Truss Calculators
« Reply #313 on: February 22, 2016, 03:57:35 PM »
I'm glad to hear that it is being put to use.  Post a picture or two once you've got your geometry where you want it.  I would love to see how it is actually being used.  I've had to take a break for a few days but I will be back to it probably next week and try to add in the raised heel with attic and scissor trusses.

Oooh, that's exactly what I'm looking for, I think.  A raised heel scissor truss.  In the Copper River basin of Alaska it can get pretty cold in the winter, so I'm looking for at least R-38 in the ceiling.  My Plan A is to construct a structural ridge beam and support it with walls and columns.  Scissor trusses can give the same vaulted ceiling but be a lot easier to construct than hoisting a ridge beam 20' up.  I did a mockup of the geometry I'm looking at and will post a screenshot of it tonight.
My cabin build thread: Alaskan remote 16x28 1.5 story


Offline Medeek

  • Journeyman
  • *****
  • Posts: 2,063
  • Structural Engineering
    • The Engineering and Design Firm of Medeek
Re: Truss Calculators
« Reply #314 on: February 22, 2016, 04:11:57 PM »
Here is a Dual Pitch 2/2 - 3/3 truss with a 12:12 pitch and a 4:12 pitch.



Still working on the gable end trusses and the advanced options involving structural outlookers.

I will be looking at raised heel scissor trusses next, those sound challenging and interesting.  Please post or send me examples of any raised heel scissor truss examples or shop drawings.  The combined pitches of the top and bottom chord with a wedge, slider or vertical web and strut will require some serious calculations and ample logic.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline ChugiakTinkerer

  • Senior Member
  • ****
  • Posts: 630
  • Building a remote cabin in Alaska
Re: Truss Calculators
« Reply #315 on: February 22, 2016, 07:22:20 PM »
Here we go...

Truss on the left is Medeek-generated based on the following (defaults otherwise):
Scissor Truss, 16' out to out span
Scissor 4/4
Top chord pitch: 12
Bottom chord pitch: 8
Overhang 24 L/R
24" spacing

Truss on the right is the geometry I'm looking for.  Is this a Scissor 6/6?  Raised heel scissor truss, 12/12 TC, 8/12 BC, 10" raise on the heel.  It would be so awesome if your plugin could generate this.

My cabin build thread: Alaskan remote 16x28 1.5 story

Offline Medeek

  • Journeyman
  • *****
  • Posts: 2,063
  • Structural Engineering
    • The Engineering and Design Firm of Medeek
Re: Truss Calculators
« Reply #316 on: February 22, 2016, 07:38:07 PM »
I'm trying to close out a local job right now, but as soon as I get it done I will look into the scissor you've described below.  Yes, I would call that a 6/6 Scissor, and with that much triangulation in that short of a span you should be good for some serious snow loads.  Actually with that steep of pitch you realistically shouldn't have that much snow load, especially if coupled with a metal roof, but its Alaska...
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

  • Journeyman
  • *****
  • Posts: 2,063
  • Structural Engineering
    • The Engineering and Design Firm of Medeek
Re: Truss Calculators
« Reply #317 on: February 23, 2016, 03:09:57 AM »
Version 1.3.2 - 02.23.2016
- Added Dualpitch truss type, configurations: (2/2-3/3).
- Metric input enabled for dualpitch truss type.
- Advanced options enabled for dualpitch truss type.



View model here:

https://3dwarehouse.sketchup.com/model.html?id=u9b6a5e53-76c4-4c9b-bce3-aaa8ffba4c36
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

  • Journeyman
  • *****
  • Posts: 2,063
  • Structural Engineering
    • The Engineering and Design Firm of Medeek
Re: Truss Calculators
« Reply #318 on: February 24, 2016, 08:45:27 PM »
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

  • Journeyman
  • *****
  • Posts: 2,063
  • Structural Engineering
    • The Engineering and Design Firm of Medeek
Re: Truss Calculators
« Reply #319 on: February 25, 2016, 09:15:35 AM »
A quick study of the general shape and layout of a 6/6 bowstring truss with different radii:

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


Offline Medeek

  • Journeyman
  • *****
  • Posts: 2,063
  • Structural Engineering
    • The Engineering and Design Firm of Medeek
Re: Truss Calculators
« Reply #320 on: February 28, 2016, 12:00:08 AM »
Version 1.3.3 - 02.28.2016
- Added Bowstring truss type, configurations: (6/6).
- Metric input enabled for bowstring truss type.



View model here:

https://3dwarehouse.sketchup.com/model.html?id=udee2767c-3da1-40b9-8d07-9e1e36989d4a

I'm not sure how common place this truss type is anymore so I will add the advanced options at a later date if requested by a user.  I can also add in other configurations with more panels if needed (ie. 8/8, 10/10).
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

  • Journeyman
  • *****
  • Posts: 2,063
  • Structural Engineering
    • The Engineering and Design Firm of Medeek
Re: Truss Calculators
« Reply #321 on: February 28, 2016, 02:03:44 PM »
Added Bowstring truss type, configurations: (8/8).



View model here:

https://3dwarehouse.sketchup.com/model.html?id=uad891cf8-30ad-4d6f-ae10-a8b7f10a2114
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

  • Journeyman
  • *****
  • Posts: 2,063
  • Structural Engineering
    • The Engineering and Design Firm of Medeek
Re: Truss Calculators
« Reply #322 on: February 28, 2016, 11:37:41 PM »
28' Bow Barrel Truss (8/8) study.



View model here:

https://3dwarehouse.sketchup.com/model.html?id=ub4c69c4f-ae02-4ad8-b17b-5eecb8d31823

Gable end trusses for this type are a bit of a question right now.  I can add this one into the plugin if there is some call for it, but I may hold off until a request is made since the code will be somewhat tedious with all the separate members that make up the top and bottom chords.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Medeek

  • Journeyman
  • *****
  • Posts: 2,063
  • Structural Engineering
    • The Engineering and Design Firm of Medeek
Re: Truss Calculators
« Reply #323 on: March 02, 2016, 05:47:46 PM »
Version 1.3.4 - 03.02.2016
- Corrected a bug in the metric unit template module.
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Don_P

  • Journeyman
  • *****
  • Posts: 4,597
Re: Truss Calculators
« Reply #324 on: March 03, 2016, 03:54:13 AM »
We don't have many bowstrings around here but I was under a steel one yesterday in the local auto shop ~60' span with 2 rows of posts inside. It's been a long time but there was a nice old wooden one on the state fairgrounds in Raleigh that was a design from their ag college.