Truss with 2 Top Chords and 1 Btm Chord

[JH75]

Hi guys,
I am trying to create a truss with 2 Top Chords and 1 Btm chord. I have setup the chords and been able to add parameters to them ie to change the height, width and the angle of the truss. Where I am stuck is how to create the web (diagonals) for each face of the truss.
I started with “Metric Structural Framing - Complex and Trusses” template.
I tried to add a Ref. Plane along one of the diagonal faces but when I change the slope of the truss the Ref. Plane doesn’t stick.

Any suggestions are welcome.

Thanks.

J

[m20roxxers]

J

I would be working with alot of reference lines to control the start and end points of the web then build up behind that with the profiles. Due to reference planes infinity extents they are not really capable of having start and end points. They also come in hand for bow trusses.

[JH75]

Hi,
I did re-think on how to create the truss. I re-started with the Standard beam template and created my top and btm chords. I then loaded a Generic Model component containing my members for the web. I still have one problem though and that is to create the array of the web framing. Also the individual web members are slightly rotated.

It is maybe not that accurate as the web members overlap with the chords ie they are not cut at the face of the chords.

Cheers,

J

[benmay]

Nice family there, I have done something similar before with much difficulty getting the array to work.

The first thing you need to decide is wheter you need to truss to array evenly either side of the centre, that means a set top or bottom release at the support, it seems you have a top release modelled at the moment.

If that is the case you then need to array the group individually each side about the centre of the truss. That is the tricky part, you will find the the truss overconstrains very easily.

I would reccomend that you first constrain the one bay, then array and do this separatly for each side. And I have found that if you need to edit the array group you will find most times you will need to delete the array and start again once you have the single bay constrained correctly

To setup the array calaculated parameters take a look at the OOTB truss familys to get started.

Otherwise is just a matter of tinkering with it until it works the way you need it.

Happy to help further if you get stuck

[JH75]

Thanks,
I haven’t had time to play around with the array yet but I will give it a go.
I tried a different approach – I made the web members face based and the used the top of the bottom chord as the work plane that way they will follow the slope top the bottom chord. The problem here is when I try to array the web members they loos the reference to the work plane.

J

[hchui]

Thank you for sharing your ideas and families. What if the lattice truss is curved as in the two attached pictures? It would it be very difficult to model!

Can it be done by creating a curve roof above the lattice truss and attach the truss to it, will the lattice truss take the shape of the roof?

I just don't know where to start. Any idea anyone?

[karalon10]

Hi
Sorry I havent actually read the entire thread here,
however I believe this truss family will at least get you started.
I just quickly did this and posted it for another thread (and then was redirected here)
So I beleive if you make some slight adjustments to this family you will easily achieve your triangular shape (its currently a box lattice)
Of note - I don't have ANY paramaters set into this family basically I sketched it up quickly, and trusses can be pretty unique so you need to decide which/what paramaters you want in there for yourself.


Hope it helps.

[benmay]

Thank you for sharing your ideas and families. What if the lattice truss is curved as in the two attached pictures? It would it be very difficult to model!

Can it be done by creating a curve roof above the lattice truss and attach the truss to it, will the lattice truss take the shape of the roof?

I just don't know where to start. Any idea anyone?

Currently the actual truss component in revit is linear only, meaning you cant create a parametric box truss, what has been done in the previous posts is creating a family with the family template "complex and trusses"

You could model the family to include parameters for the curve of the roof, but I would think it would be very difficult to acheivec
An easier solution is to model a mass family (inplace is probably simplest) and then you can simply select the curve of the mass to achieve your curve with your modelled "complex and truss" framing family

If you search through Augi there has been a few discussions regarding curved roof framing, so long as your framing family for the truss is modelled correctly it will work the same as a simple beam, you might just have issues at the support getting the correct interface

[hchui]

Currently the actual truss component in revit is linear only, meaning you cant create a parametric box truss, what has been done in the previous posts is creating a family with the family template "complex and trusses"

You could model the family to include parameters for the curve of the roof, but I would think it would be very difficult to acheivec
An easier solution is to model a mass family (inplace is probably simplest) and then you can simply select the curve of the mass to achieve your curve with your modelled "complex and truss" framing family

If you search through Augi there has been a few discussions regarding curved roof framing, so long as your framing family for the truss is modelled correctly it will work the same as a simple beam, you might just have issues at the support getting the correct interface

I think Revit Structure's truss capability should extend to include generation of parametric lattice truss and other complex trusses. This should be included in the wishlist!


Autodesk....are you listening?

[econnolly]

Hello All

I am trying to create custom open web steel joist with curved top chord (i.e. bowstring joist) and i am having some difficulty. What is the best way to go about this? Modifying an existing K-servies joist or building an entirely new joist utilizing the TRUSS modelling tool?

I am a newbie at Revit Structural and would greatly appreciate any tips or advice.

THANKS!