Author Topic: Truss Calculators  (Read 177967 times)

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Offline Medeek

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Re: Truss Calculators
« Reply #100 on: October 13, 2015, 08:35:50 AM »
I've had a number of requests for monopitch or monoslope trusses.  Shown below is a sample of potential configurations of this type of truss.  Has anyone ever seen a (5/3) or (6/4) or a (3/1) monopitch truss?  The first number is the number of top panels and the second number is the number of bottom panels to clarify.

Nathaniel P. Wilkerson, P.E.
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Offline Medeek

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Re: Truss Calculators
« Reply #101 on: October 16, 2015, 01:43:48 AM »
The left and right overhangs can now be set independently, however the right overhang defaults to match the left overhang to help speed user input:



I've also created a new page for the plugin with some basic documentation:

http://design.medeek.com/resources/medeektrussplugin.html

Just an FYI, the energy heels are enabled fully for the fink truss but not for any other truss type and the TRIAL version is actually not limited in any way.  I will probably keep it that way until the plugin is significant enough to actually warrant charging for it.
Nathaniel P. Wilkerson, P.E.
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Offline Medeek

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Re: Truss Calculators
« Reply #102 on: October 17, 2015, 05:10:34 AM »
I'm testing the attic truss option. At the moment I've only got one configuration which is probably about right for an attic truss that spans about 24-28 feet. You can see below that pushing it out to span 36 feet is a bit of a stretch:



The piggyback option is enabled by enforcing a max. height in the inputs.

36' span, 18' attic width, 9' ceiling 12/12 pitch, 11-7/8" bottom chord.
Nathaniel P. Wilkerson, P.E.
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Offline Medeek

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Re: Truss Calculators
« Reply #103 on: October 17, 2015, 11:50:47 AM »
This is the same truss I used in my 28'x48' garage:



Now I need to work on the energy heel option for this truss.

Nathaniel P. Wilkerson, P.E.
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Offline Medeek

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Re: Truss Calculators
« Reply #104 on: October 17, 2015, 02:29:45 PM »
24' truss without a piggyback (Max. Height set to "NONE"). 2x6 TC, 2x10 BC, 2x4 overhangs.  12' attic width, 8'-1 3/4" attic height.

Nathaniel P. Wilkerson, P.E.
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Offline Medeek

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Re: Truss Calculators
« Reply #105 on: October 19, 2015, 01:37:48 AM »
22' truss, notice the change in the web configurations as compared to the 24' truss. 



There still may be a few kinks to work out in the algorithm that determines how many webs to place but overall I'm pretty pleased with what I have so far. 

I've officially added the attic truss updates to the plugin so they are now live.
Nathaniel P. Wilkerson, P.E.
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Offline Medeek

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Re: Truss Calculators
« Reply #106 on: October 19, 2015, 11:16:25 PM »
Trusses are now created as components with each individual member of the truss a group. Arrays of trusses are multiple instances of the same component.

I think this plugin may actually have some potential now.

A couple more screenshots for fun:





I need a break for a few days on this but when I come back to it I'll knock out monopitch trusses next.
Nathaniel P. Wilkerson, P.E.
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Offline Medeek

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Re: Truss Calculators
« Reply #107 on: October 20, 2015, 05:34:45 PM »
Howe truss type is now active. 

The latest plugin version is 1.0.4.  I would highly recommend downloading the latest version since I have also spent some time this morning cleaning up my code and removing global methods and variables so that I don't clash with other extensions or modules. 

Nathaniel P. Wilkerson, P.E.
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Offline Medeek

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Re: Truss Calculators
« Reply #108 on: October 20, 2015, 10:45:34 PM »
Monopitch trusses are also now live:



Currently the 2/2 and 3/3 configurations are available, more of this truss family will be added after I address the metric issue.
Nathaniel P. Wilkerson, P.E.
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Offline Medeek

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Re: Truss Calculators
« Reply #109 on: October 21, 2015, 11:57:45 AM »
I'm looking at adding in scissor trusses.  Below is a matrix of common scissor truss configurations.  Once they get much larger than a 6/6 I think they probably go to site assembled half trusses, I'm not entirely sure since I don't have any drawings or diagrams of anything larger than a 6/6.

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Offline Don_P

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Re: Truss Calculators
« Reply #110 on: October 21, 2015, 06:26:41 PM »
I vaguely recall one with a girder truss ridge and half trusses but it was cut up with dormers onto that ridge as well.

Offline Medeek

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Re: Truss Calculators
« Reply #111 on: October 21, 2015, 10:45:58 PM »
For the common truss types I've configured the plugin to detect the SketchUp template units and display a metric UI.  I've also replaced the x/12 system with degrees for the metric interface.  All member sizes and other dimensions are open for the metric interface as well.

Go ahead and give it a whirl, if it checks out then I will go ahead and update the attic and monopitch UI with the metric option.
Nathaniel P. Wilkerson, P.E.
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Offline Medeek

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Re: Truss Calculators
« Reply #112 on: October 22, 2015, 08:38:44 AM »
With the truss plugin I have been primarily focused on typical MPC wood trusses however the potential for other truss types does exist.  I'm wondering if some of the more exotic timber truss types can be codified in a similar way so that one can generate possible configurations and experiment with their design.

One interesting truss type that comes to mind is the Hammer Beam truss/frame as shown below:



Some other variants (an probably quite a few more):

Nathaniel P. Wilkerson, P.E.
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Offline Don_P

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Re: Truss Calculators
« Reply #113 on: October 22, 2015, 01:56:49 PM »
The math is the same for heavy timber just the design values and magnitudes change.
A hammer beam is a broken truss, or rather it is not a truss. When they do not fail it is due to heavy walls, buttresses, or good diaphragm in the roof... it certainly isn't the hammerbeam's fault if the roof doesn't splay.

Offline Medeek

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Re: Truss Calculators
« Reply #114 on: October 22, 2015, 02:36:05 PM »
I actually like to call them timber frames since the current practice seems to be  to frame up the wall posts with the upper section as one unit.  They are the crown jewel of the timber framing industry as one web site puts it.  The problem with them is the considerable outward thrust because the truss is "broken".  Typically these are quite custom so I'm not really interested in putting them into my truss calculator (load calcs are probably best run in RISA 3D) but it might be interesting to have them in my plugin just for the geometry and the ability to play with the variables that affect the look and feel of the truss.
Nathaniel P. Wilkerson, P.E.
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Offline Don_P

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Re: Truss Calculators
« Reply #115 on: October 22, 2015, 06:11:41 PM »
I would call what is pictured in your drawings a "bent", it can be either timberframed or post and beam, depending on whether wood or steel connected, and there is plenty of room for generalizing in any of that. In bent frame construction a section slice is tipped up into place, these are connected by girts. Another method, box frame, would be more akin to platform framing. Posts, plates, and truss or common rafters on top of or integral with the plate.


Basically, If they can get a computer to draw it, they will build it.
The thrust has to be taken care of by some other means, that should be made clear somewhere in there. I went to one workshop where a topic was how to retrofit failing hammerbeams. He had plenty of pictures. They are a shining jewel but not on a cap I'd want to wear.

 One way to build one is to incorporate a steel rod across the gap, you'll see that in most modern versions unless there is another bracing element like adjoining wings.

This is a good link if you don't already have it;
http://timberframeengineeringcouncil.org/library/#tech bulletions
« Last Edit: October 22, 2015, 06:38:12 PM by Don_P »

Offline Medeek

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Re: Truss Calculators
« Reply #116 on: October 23, 2015, 12:59:39 AM »
This is a good link if you don't already have it;
http://timberframeengineeringcouncil.org/library/#tech bulletions

Unfortunately, I don't get a lot of timber frame engineering opportunities in this area so I probably haven't opened that publication in a while.  Looks like I've got some reading to do.
Nathaniel P. Wilkerson, P.E.
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Offline Medeek

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Re: Truss Calculators
« Reply #117 on: October 23, 2015, 01:01:23 AM »
I was thinking about adding the scissor truss family to my SketchUp plugin until I realized that the calculation of the scarf of the bottom chord was a bit more complicated than your typical common truss with a zero pitch bottom chord.  When I actually sat down and did the  math it became clear how much more complicated it actually was.  If anyone cares to check the math I would be very grateful.  I will probably run it into AutoCAD tomorrow and graphically check the geometry against the equation, they should give the same result.

Nathaniel P. Wilkerson, P.E.
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Offline Medeek

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Re: Truss Calculators
« Reply #118 on: October 24, 2015, 01:39:23 PM »
The equation was spot on, my faith in trigonometry is restored:



Version 1.0.5 - 10.24.2015
Added Scissor truss type, configurations: (2/2), (4/4).
Metric input enabled for scissor truss types.
Nathaniel P. Wilkerson, P.E.
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Offline Medeek

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Re: Truss Calculators
« Reply #119 on: October 26, 2015, 12:39:54 AM »
Version 1.0.6 - 10.25.2015
Added floor truss type, Modified Warren - System 42.
Metric input enabled for floor truss types.
Top and bottom bearing option enabled for left and/or right end of floor trusses.
Ribbon cut option (top) enabled for left and/or right end of floor trusses.



One central chase that can be position relative to the left end of the truss.  If the chase becomes closer than 1/4 the span to either end it will flag the user and re-position.  Also some logic to check the chase size to span ratio and absolute max. chase size (24").

System 42 or 32 floor trusses using the modified warren configuration which seems to be the most popular for this type of floor truss.  Top bearing configuration includes an additional slider for extra strength and a vert. Note the change in diagonal directions when comparing a top to bottom bearing floor truss, I was not aware of this until studying them in some detail.  Typical panel length is 28" but this can also be set by the user to any value.
Nathaniel P. Wilkerson, P.E.
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Offline Don_P

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Re: Truss Calculators
« Reply #120 on: October 26, 2015, 04:38:18 AM »
Makes sense, I had never noticed, the first web becomes a tension member... if so I'm guessing quite a connection.

Offline Medeek

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Floor Trusses
« Reply #121 on: October 26, 2015, 05:03:03 PM »
Floor trusses 40' span, 60' bldg. length, 24" deep.



Notice these are top chord bearing trusses with the diagonal webs reversed from the bottom bearing trusses in the previous post, this is by design.

A few years back (when I was in college and working construction on the side) I remember framing up a custom home with these.  I don't think much over 40' is recommended but I could be wrong.  I'm curious as to what the longest span (clear span) anyone has seen with these type of floor trusses and what is the max. depth.
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Offline Medeek

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Re: Truss Calculators
« Reply #122 on: October 26, 2015, 05:11:39 PM »
Just out of sheer awe I have to post these two pictures I found at Select Trusses website:

My one worry with commercial buildings constructed using light frame construction is fire resistance.  This building wouldn't have a chance if a fire were to occur:



A quad fink truss (10/9) with a raised heel (slider):

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Re: Truss Calculators
« Reply #123 on: October 26, 2015, 06:04:37 PM »
Just out of sheer awe I have to post these two pictures I found at Select Trusses website:
............  This building wouldn't have a chance if a fire were to occur:
.

That nice latticework would be like the handful of twigs used to start a campfire.
Just because something has been done and has not failed, doesn’t mean it is good design.

If you didn't have the time or money to do it right in the first place, when will you get the time and money to fix it?

Offline Medeek

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Re: Truss Calculators
« Reply #124 on: October 26, 2015, 06:22:30 PM »
That nice latticework would be like the handful of twigs used to start a campfire.

Exactly what I was thinking, well aerated and the wood member size (kindling) would be a perfect fuel.  If a building like this were to catch fire it would burn very quickly and aggressively. 
Nathaniel P. Wilkerson, P.E.
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