Best practise to model trusses?

[klausstroehl]

Hi, what is the best way for modelling trusses?
Usually I model them in an empty project, group the elements such as beams, details and reference planes. Then i copy the whole group into my "real" project. The problem with cutting beams at ref.planes or with the coping tool is that changes wont adapt to all other group members. Only the one you change will have the coping. I want to read out the cut length parameter so i have to model the verticals and diagonals accurately.
What do you think? Any experienced truss modeler out there?
Cheers, -Klaus

[Craig_L]

Theres no really easy way around it.
Just ask yourself if you really need to clean up every single truss though, or only the ones you see in a section or view.
Usually they will render jsut fine without having to clean them up.
If you are using them for material lengths etc, I guess thats a different story, but I would question the accuracy of them in that regard anyways.
Grouping is an option, I also try to clean one up, select all members and copy them as required but this can cause other follow on problems also. Most of the work-arounds will have issues with them, sadly this is how the truss families work.
Another option that I used for making my own vertical wall truss elements (PT BRACE) is to create your own using extrusions, and trim that up within the family creation. You can build in some general things to allow this to flex, and nest in bays etc to allow more flex. This family is very basic and will break if made too large but it works for what I need it for. Have a look at this and see if something like that allows you greater control (obviously this is for a wall so you would need to create yours differently but as a guide this might help you)
As I say, this is NOT a perfect example, mine breaks under certain conditions, but it works for the limits I require so I have continued to use it. You could allow this to flex better with nested bays but I am not really advanced enough at the moment to perfect that (and its over kill for what I needed)

[Jheadley13]

This is how i model trusses, forget the "truss" tool that revit provides. Keep in mind with my method, that, this will probably not schedule properly if that is your plan.

Basically, i just "mass" the 1st truss, group that truss, and copy as necessary. That way, if the truss members ever change locations, which they always do, the group will automatically update.

Hope this helps,

Jason

[klausstroehl]

Thanks for your help!
We will model the trusses manually in our projects with ref. planes and real beams and group them. As you said, sceduling is a problem with a custom family.
We´ve decided to use coping/cutting the ends only for the trusses we really display on plans. Another problem with "detailing" every single truss is that file size goes up rediculously, 50MB for an empty project with around 50 trusses, all the same group type.

Cheers, -Klaus

[klausstroehl]

By the way... is it possible to set the profile of your sweeps as a "Profile-Type-Parameter"?

[Craig_L]

Theres any number of ways to do that, I used sweeps because these cold form sections are not really standard they are specialised for that particular product. However, you could nest in actual beam families, shs families etc in place.

[klausstroehl]

Yep right! But, nesting in too many beam families would not be our goal, for performance reasons?! Thats why I thought using profile-families for the sweeps as I did in the family attached. But I´m not able to flex the profile in a project later on....

[Craig_L]

When you say flex the profile, are you talking about the member, or the entire truss?
The truss can still flex, by building in the required paramaters.
Nesting in the extrusions should not really be cause for too much slow down in performance, it just means you arent reinventing the wheel for the profile shapes. You can also nest in bays which will flex based on the external frame, you can really make this as complex as you like. The problem will be nesting in too many little details, but even still, I imagine that its not going to cause a great deal of performance problems.
There are some good tutorials and a really good worked example on the power of nesting here

http://blog.cadway.com.au/2010/10/ma...ic-mobile.html

Its not a truss but the process remains the same and as you can see this is quite a complex object, and doesnt really cause any problems with performance.

[klausstroehl]

Hi, I wanted to change single members... Nesting in too many model elements will cause performance problems. Therefore I would have used the option of changing the seep-profile but as i said, I can´t find a way to change it by parameters.
Thanks for your help!!