Roof truss view in floor plan and 3D views don't match up

[wile e coyote genius]

Please accept my apologies if this is in the wrong forum as I was not sure where it should be. In the design of my building I had a need for a truss so I selected the "object" icon and selected the appropriate truss from the library. I placed the truss where needed. When it come time to cost out the truss I was asked to send a drawing of the truss with dimensions. Since I had never had to this before I didn't know how to create the drawing in AC but I could easily create it in my MCAD software. To that end I started to recreate the truss which is where I began to run into problems. If you look at the picture showing the 3D and floor plan views you will see that they don't align with each other leading me to wonder what the rectangular boxes shown in the floor plan actually represent. I made many dimensional checks on both views in AC and nothing lines up. It should also be noted that when in the 3D mode the truss is created as a single item which means that the only snap points are on the extremes of the item. There aren't any snaps where the web pieces meet the chords making measurements difficult in the 3D view. It's not possible to get dimensions from the floor plan view as nothing lines up with the 3D view. I am hoping that someone might be able to explain why the floor plan view and the 3D views don't correlate with each other and what do the square boxes in the floor plan view represent. Also, is there a way to add snap point at the ends of the web pieces?

Thanks in advance.

[DGSketcher]

The "boxes" are appearing as a consequence of your Floor Plan Cutplane Settings that you have under your plan view settings. They show sectioned timber at the set cut height.

To convey the dimensions of a truss, would you not be better dimensioning a section view?

[wile e coyote genius]

Hello DG:

Never tried dimensioning a section view but after some effort I figured out how to do what you said and it works. The dimensioning tools work but aren't very intuitive as compared to MCAD software. I also find them not as accurate. In my case the roof has a pitch of 23.21 degrees but when I dimension it shows 23 and I have set the angular units to 2 decimals. In the end it will work it will just take a lot more effort.

regards.

[mthd]

Why stress so much about something that a truss manufacturer would create with their own specific software ? I used to design trusses back in the mid eighties with Bostich software. As long as your roof parameters are exact, they can certainly do the rest for you. Your Truss webbing may not be dead exact either. Of course if you are replicating an already built truss then that’s a different scenario. 

[wile e coyote genius]

mthd: You are correct that I could have the truss supplier do all of the design work but they don't do it for free especially when there is no guarantee that they will be the supplier. In my situation the design is to reduce costs as much as possible which means not paying for outside engineering that we can do. Then again the trusses could be built on site from precut lumber. After doing our own calculations the truss we selected from the library will meet our needs and the dimensioning is for the cutting of the pieces.

DG: Based on your suggestion I created a section view for the truss and started dimensioning it with the dimension tools only to find a new issue - accuracy.

In the picture you will see the measured angle of the roof using the section view (top) and the actual design value from the object settings (bottom). I checked the dimension text presentation and it is set for 2 decimal places. I am not sure I can trust the dimension values shown. Any thoughts?

[Steve Jepson · Accepted solution]

Forget the Truss Tool.  Use the .pdf or better yet, the .dwg or .dxf (if you can get it) from the manufacturer.

Model the Trusses per those profiles.  Get the lines to scale, then use a slab to fill the truss area - and also click-click-click to cut holes in the Slab to form the webs.   View from Top, save as model part with the same ID as the truss manufacturer gave it.   There are very good reasons to model the Trusses.  Or at least one of each profile is needed to confirm the fit.  Just like everything else, the truss manufacturers' technicians are not always really good at what they do.    I frequently find mistakes.  Also, the modeled trusses are a big help in being able to communicate efficiently with the manufacturer about alternatives to how the trusses might be fabricated in a way that works better for one reason or another.     

Also, ArchiCAD will display the angles in degrees to (4) decimal places - if you need it that way.  

There is a reason why roof pitch is used rather than degrees so often.  

[DGSketcher · Accepted solution]

You need to look at configuring your dimension settings in Project Preferences, create your own style if necessary. AC will display as accurately as any construction fabricator can manufacture, unless you are designing precision engineered components, in which case AC may not be the best solution!

[wile e coyote genius]

I gotta ask, are you related to the musical singer/song writer Carley Rae Jepson? As for trusses, I was trying to model the one I used from the AC library with my MCAD software that allows me to create a .3ds file which I can then use in AC and allows some modifications. As for the angle vs pitch of the truss, in my case I just provided the truss height and length and AC automatically calculated the angle. Anyways, I think I will stick to creating the truss in my solid modeler and then turn it into a .3ds file and import it into AC.

Thanks for the reply

[Steve Jepson]

As for Carley Rae,  Yes.  She is my daughter.    

[Steve Jepson · Accepted solution]

Just kidding 😀.  I don't know if we are related or not. 

As for the Trusses.  this is a link to a terrible video - but it might show something useful.

Step 1 - Place External Drawing ( .pdf in this example)  of Truss Profile

2 -- Explode 

3 -- Select the resulting fills of the Truss Profile and Consolidate into one fill

4 -- Resize to Scale per dimensions of the Truss in the .pdf

5-- Tweak if needed for precision that may or may not be accurate.

6-- Select Slab, make it 1 1/2" thick, convert Fill to Slab

7-- Spacebar Click to cut holes in the slab to create web members

8-- Save as Object

9-- Plans in Modle.

See pathetic video -  I didn't have time to do it properly.  

https://app.screencast.com/M2N2qnPABt453

It's a lot faster once you get the hang of it.  Just a few minutes per truss profile.  It helps if you can get precision .dwg or .dxf to work with, but a .pdf is usually just as good because the .dwg and .dxf are not any more accurate than the .pdf.