Roofs: Slabs, Roofs, and Trusses revisited.

[twiceroadsfool]

Ive already weighed the pro's and con's of each "unRevit" approach to this, but im curious what the rest of you are doing. Heres the issue:

Modeling a Large Hip Roof that has Trusses underneath it. For the moment, im entirely discounting Copy Monitor, since it doesnt work on Roofs. It works on Floors, but thats useless unless Arch builds it as a floor as well. That part isnt very valuable to me, since the Roof isnt built in Revit the way it will be built structurally anyway.

So i have three options:

1. Use Slabs (one face at a time)
2. Use Slabs (Modify Sub Elements, Split lines, raise ridges)
3. Use Roofs.

Slabs:

Can show the Decking Profile, if there is one,
Can only have one slope defining line, unless its done by Modify Sub Elements.
If its done in "planes" with slope defining lines, you basically cannot attach trusses to it, since the trusses will run under multiple Slabs and the profile becomes invalid since you cant attach to multiple at the same time.
If i use Modify Sub Elements / Split Lines, etc, i can use this perfectly with truss attachments.

Roofs:

Wont show the decking Profile, if there is one, so theres a bunch more detailing to do in a lot of views.
But, i can directly copy and paste it from the Architectural Model. Then i just have to edit where they built it incorrectly.
This means i can use regular values for slope defining lines, and attach trusses to it.

Im not new to Revit, so much as new to Structural. So i understand the woes and realities of "using the wrong Revit tool," but im a bit put off with Structural Roofs. RIGHT NOW were not focusing on any integration with RAM and their other Analysis packages, but thats coming down the road (possibly). Im not concerned terribly with Catagories and visibilities, as ive been on the architectural end with engineers who have used slabs, and a filter here and there keeps everything contiguous.

For the analytical model, it appears the Slabs on a face by face basic is the only one that loads properly, if im looking at it correctly. So im not sure thats a paramount concern, but im curious how its affecting you.

FYI- I know this is less of an issue for "basically flat" roofs, with simple shape editing for slopings to drains, etc. But for these types of projects, which we do rarely, id be interested to hear what you all do.

[twiceroadsfool]

Well, im still hoping for feedback from some of you who use it and have gotten through this vetting process, but heres another straw to the mix.

Roofing2.jpg- In section, a truss that is "attached" to a regular Roof in RST. The Centerline of the Top Chord follows the bottom edge of the roof, and thus the member pushes in to the roof. Now, its as simple as unpinning the member, and setting the Z-direction justification to top instead of center, but hving to do that for every truss will sort of suck. I mean, i can sweep select and do it, but i cant even group them since the point is each truss will be different as they attach to the declining Hip.

Roofing3.jpg- In section, a truss that is "attached" to the Shape Edited Structural Slab in RST. How about that, it knows to change that Z direction justification to Top automatically. For a Floor. But not for a roof, LOL.

[m20roxxers]

I can't really speak for everyone, but generally we don't bother with trussing at all, it is done by the truss manufacturer or if it is a rafter design with use the tools4revit to overcome our timber designs.

The truss tool itself I only have used a handfull of times and these have been on some train stations and a stadium and completely customised.

Only with very complex steel and timber roof will we design otherwise we leave up to our standards.

[twiceroadsfool]

Alright, thats a decent option if you have the contractual allowance to not show them. unfortch, we have to. But either way, what do you do for the roofs? Roofs, or slabs one of two ways?

The truss issue is working itself out with our Shape Edited Slabs, but im just surprised we had to go that road, instead of using Roofs. Furthermore, i cant believe the ROOF tool is under "Architect" in RST. So Engineers dont deal with Roofs at all? LOL

[troberts]

We have had beter luck using a slab as the roof and then editing the slopes. THat way you can attach the top chord of the truss, but it is still an ordeal that requires a few "Revit workarounds".

[benmay]

If I have a Arch model, I try to stay away from creating my own roof altogether. And at the moment we cant copy/monitor roof elements (but saying that we dont even trust c/m on floors)

My prefered approach is to model all framing to reference planes, and if you have a linked model this is quite easy by just selecting the linked model roof planes in section

But looking at the layout you are talking about, I understand just selecting the roof or floor would be the way to go, I think floors are easier to setup to the required levels but dont have all the functionality that roof elements have for eaves etc.

If you are doing a large amount of these sort of truss layouts I would suggest looking at the truss+ tools from tools4revit, it works in a similar way where you select the roof element and it basically creates your truss layout for you based on guidelines you set. I believe they come in as non parametric but you can run the application again.

I have a copy of the software, but have never had the right project to use it on. I think the main problem with using a floor is that you can easily over modify the floor and have to reset it which may cause major problems for your trusses.