topic Re: AC17 T-Junctions in Modeling

AC17 T-Junctions

KeesW — Wed, 24 May 2023 07:11:49 GMT

Have got my AC17 and thought that I'd try the T-Junction of a timber stud wall lined with plasterboard both sides. One wall was copied from the other so that they are both identical. Plasterboard value is 400, whilst core is 500.

The identical situation created with AC16 worked perfectly - first time.

It seems that 'automatic' wall junctions are going to take some learning.

Re: AC17 T-Junctions

Eduardo Rolon — Fri, 26 Jul 2013 13:52:30 GMT

Start here:

http://www.graphisoft.com/archicad/archicad_17/bim_details/#priorty_based_connections

The new Materials and PBCs require a different way of thinking how we model intersections. Basically the New Materials have intersection priorities in your case you need to check that the Plasterboard Material have a lower number than the Timber Material and that the wall "overlaps/intersect".

Also check in your preferences if you have the intersection Legacy option on.

and please read the Migration Chapter in the help file.

Re: AC17 T-Junctions

KeesW — Sat, 27 Jul 2013 00:32:22 GMT

Thanks Elrolon.
I did look at those references before I got AC17 and will obviously have to do so again - more thoroughly!

I didn't think that I needed Legacy because the walls were taken directly from a freshly installed AC17 library. Note that the timber core has a higher number than the plasterboard.

Re: AC17 T-Junctions

Eduardo Rolon — Sat, 27 Jul 2013 00:57:33 GMT

This might sound weird. Did a test here and was getting your error even after verifying the BMat Priorties twice.

Third time was the charm I had edited the priorities on one BMat and picked another for the composite. Can you verify that you didn't make the same mistake I did.

I have seen a bug when you create a new BMat and AC switches from editing the new one to editing the one you copied from which might be another item to check.

Re: AC17 T-Junctions

KeesW — Sat, 27 Jul 2013 12:34:29 GMT

Ejrolon

I've tried it again and it didn't work. No I didn't make your mistake - although I might have made others.

What I did discover is that increasing the junction property of the leg of the 'T' from 8 to 9 whilst leaving the long arm at 8, removes the plasterboard in the junction. It is not perfect because it still leaves a line. I've attached a screen shot. What am I missing here?

Re: AC17 T-Junctions

Eduardo Rolon — Sat, 27 Jul 2013 12:49:53 GMT

You shouldn't need to use Junction order to fix this.

Lets take it from the Top.

BMat settings: Plywood Intersection Priority = 300. Test Fill = 500

Re: AC17 T-Junctions

Eduardo Rolon — Sat, 27 Jul 2013 12:50:28 GMT

Composite Settings

Re: AC17 T-Junctions

Eduardo Rolon — Sat, 27 Jul 2013 12:52:29 GMT

result

Re: AC17 T-Junctions

Eduardo Rolon — Sat, 27 Jul 2013 12:53:09 GMT

With wall intersections off.

Re: AC17 T-Junctions

KeesW — Sat, 27 Jul 2013 12:54:16 GMT

I've created correct T-junctions with cavity brickwork - but it doesn't work with plasterboard lined timber framed walls. This, unfortunately, is one of our most common wall types.

Unfortunately, brickwork doesn't present correctly. I attach another T Junction in brickwork How can a single skin brick wall present as it does in cross-sections - it should only show horizontal joints. This is the kind of cavalier and careless programming that taints the true usefulness of archicad's 3D presentations.

Re: AC17 T-Junctions

KeesW — Sat, 27 Jul 2013 13:01:15 GMT

Ejrolon

"With wall intersections off"????
Where and what is this command? I never had to worry about this before. Is this another AC17 improvement?

Re: AC17 T-Junctions

Eduardo Rolon — Sat, 27 Jul 2013 13:11:33 GMT

It has been there since AC07 which was the first one I used it is a display option. I only used ut so you could see how the walls were drawn

Re: AC17 T-Junctions

Eduardo Rolon — Sat, 27 Jul 2013 13:25:11 GMT

On the other item you will need to use Align 3D Texture to get the Materials to behave. If they don't then you might need to create your own texture.

Re: AC17 T-Junctions

KeesW — Sat, 27 Jul 2013 21:52:54 GMT

Wall junctions off: I know about that view setting but thought that there was something new.

Re: AC17 T-Junctions

KeesW — Sun, 28 Jul 2013 11:34:10 GMT

Problem solved!
I used a new default timber stud with plasterboard both sides to create the 'T-junction". It didn't work properly. I've now re-checked the settngs and found that both core and linings had the same value of 500. Graphisoft AUS would create a default composite wall with the same value for skins is only known to them. But, I should have double checked before. Sorry for raising the issue.

Re: AC17 T-Junctions

KeesW — Sun, 28 Jul 2013 12:43:21 GMT

One more comment and then I'll stop with this issue. I've discovered how Graphisoft AUS created a composite wall with the same skin number in the standard AC17 library. They used 'plaster' instead of 'plasterboard' linings on 70mm and 90m stud partitions. Plaster has the same skin number as timber stud (500) whilst plasterboard has a lower skin number. The standard 50mm stud partition included in AC17 AUS library has plasterboard, and NOT plaster, linings and T-junctions created with this wall type work correctly.

An easy mistake to make and a warning to us amateurs out here to take care when creating new composite walls!

Re: AC17 T-Junctions

Laszlo Nagy — Mon, 29 Jul 2013 12:53:19 GMT

Just out of curiousity I checked the INT AC 17 Template file: no two Building Materials have the same Intersection Priority Number.
Which is probably a good advice in general when creating Building Materials.
The fact is: when two intersecting skins have the same Intersection Priority Number, then there is a priority order among element types that goes like this from strongest to weakest:

Morph > Beam > Roof > Shell > Slab > Column > Wall

But if it is the same element type (such as tow Walls) and their Intersection Priority Numbers are the same, it is up to chance which will be stronger.
To avoid such possible cases it is advisable that no two Building Materials have the same Intersection Priority Number.