Structural nodes

[yorik]

There are now a couple of more tools to Arch structures ( see issue #2356). Basically, now:

1. A new property was added to the ViewObject of Structures, called "NodesType". It can be "Linear" (default) or "Area".
2. Arch structures can have not only linear nodes, but also planar nodes. For this, 1) There must be at least 3 vectors in the "Nodes" property of the object, 2) the "NodesType" property of their ViewObject must be set to "Area".
3. When the nodes calculation is automatic (that is, if you never touched them manually), when setting the Role property of a structure to "Slab", it will automatically become a planar node (there will be more than 3 vectors and the NodesType will be set to "Area").
4. When editing a structure object (double-click), a couple of new tools are available in the task view: 1) reset the nodes to automatic calculation, in case you modified them manually, 2) edit the nodes graphically, works the same way as editing Draft wires (in fact it's the same tool that is used), 3) extend the nodes of the edited object until it touches the node of another object, 4) make the node of this object and another one coincide and 5) toggle the display of all nodes of all structural objects of the document on/off

Now, I think it begins to become handy and comfortable to work with these structural nodes and design decent analytic schemas. I will try to build a small example next.

Now, next on the TODO list would be: Now, what do we do with that? I had thought of 1) exporting to pybar and 2) exporting to IFC. I believe for IFC, we could export the nodes "as is". I'm not sure pybar is still an interesting/useful option, seeing the development of FEM. But maybe we could start thinking of interacting with these nodes from FEM now...

Any more input/ideas from people who understand analytic models better? (*hust* bernd *hust*)

[saso]

It sounds great Yorik!

Quite a long time ago I made for myself a very simple model, just to help me visualize the idea. It is a very general idea about the very wide concept of the BIM.

One idea out of it could for example be, to have an option when creating an architectural wall, to also automatically at the same time create the different analytical models (as I understand this is already in your plan, at least for structural model).

But on the other hand it would for example also be interesting if we have for example just an analytical model (for example an structural model) to be able to automatically create an architectural and energy model out of it (of course also could be from just an energy model to others,...).

Another interesting thing would be to be able to export our models to formats that different analytical tools would understand, FEM is already a good example of this and if I remember it correctly you are looking in to support for gbXML, it would be another great example. Some of this tools could be integrated in to FreeCAD, some could be standalone, some we could maybe even write ourselves (if nothing big and complex, maybe at least some simple scripts to check this and that).

And even if the above ideas are mostly about automating things, I fully agree and love that we also would have the possibility to work on and tweak this models manually. Anyway it is a large space of possibilities and it is nice to see things moving

[yorik]

Yes, energy analysis is also on my list. I'm progressing a bit with gbxml export, but i would need a gbxml-capable app to check. I'm trying to get openstudio to compile here, but it needs heavy modifs to work on a recent system, it seems to be using libs from one century ago.

Nice model... yeah, pretty much the kind of data we need...

[saso]

I had the idea to attack the gbXML from the other side, mostly just as an coding exercise for myself I was thinking to try one day to write a python script that would import some of the examples that can be found on this page http://www.gbxml.org/Sample_GreenBuildi ... bXML_Files (so an importer instead of an exporter), but I did not yet find enough time and courage to do it

In its basic form it would create just a simple model (probably of mostly just faces) that would look something like the thing in the energy model group in arch.FCStd. In a more advanced version, the script would also try to recreate the architectural elements out of the energy model...

[yorik]

This is what you can obtain pretty quickly with the above tools:

screenshot.jpg (136.37 KiB) Viewed 4734 times

[bernd]

Any more input/ideas from people who understand analytic models better? (*hust* bernd *hust*)

Wow what a great news. It will take some time to really test this in conjunction with FEM. I'm quit busy with some other stuff at the moment. But for sure I will come back report may opinion and make some test with FEM.

BTW. Nemetschek Allplan has such feature too. You can just export them to ifc for the engineers. But they do not care about connection of the areas and lines. The just stop and leave lots of holes. Since you can not edit the structural axes and areas at conntection points it is Really poor and not usefull at all. Lot of people complained about in the last few month but nothing has happened. Seams FreeCAD can it better already .

[yorik]

A question: I see that in Revit, when doing analytic models, walls are included, even with their windows. In saso's example it's there too.



Is that really useful? I believe it can, in case of a concrete wall that is part of the structure. But in 90% of the cases I believe you would consider a wall as a simple continuous load, right? What about load bearing masonry? How does that fit into an analytic model?

[saso]

It is probably best to wait for bernd for the real answer but yes, I believe such faces are very useful for them, for both walls and slabs (I am not sure if it is useful just for reinforced concrete or also other types), I generally don't work with this but I do often get to see such analytical results back from structural engineers, they changes this faces to 2d meshes and do the fem calculations on them...

Also I think for horizontal elements like beams (and slabs?) it is common to have the option to chose if the nodes should be on top, center or bottom of the structural element. I guess for vertical elements like walls and columns it is always center (in case of for example multi layer wall, it is center of just the core structural part, without insulation).

And, I believe the main idea is not for it to represent loads (loads as I know are added additionally) but to make a fem calculation of the element (wall/slab) deformation under loads. I guess the reason and the idea behind such simplified analytical models is that doing fem calculations on the real 3d shapes of elements for a full building is computationally just too complex, maybe in ten years or so it will get more common

[bernd]

There are two possibilities of analytical models for buildings.

- walls bear the load just from top to bottom. They take the load from one slab to the next one. The software calculates one slab by the next one and adds the load from the floor above. The loads gos from top to bottom in any case. In such a case the walls are just loads and the faces are not needed for a structural analysis. FreeCADs FEM does not support this kind of calculations at the moment.

- walls bear load like a beam would do. Imagine a long concrete wall. On top of this wall there are tree floors with walls, but under this wall (in the next floor) there is no wall. The wall can bear the load like a beam. In fem it is possible to use the abilitiy to bear loads as a slab far all walls. Actually it is what the FEM module in FreeCAD does. With this the load could walk throug your building from bottom to top and again to the bottom depending on the stiffness of your structural members.

Means yes we should have structural faces for walls too excluding the openings ! Means the structural face should consider the opening. If not it is difficault to create an analytical model from the building.

BTW. In real BIM a wall is just a Structural Element with a role too. We hopfully will not run into trouble one day because we have structural object and wall object but in Reality a wall is just an structural object too.

[saso]

BTW. In real BIM a wall is just a Structural Element with a role too. We hopfully will not run into trouble one day because we have structural object and wall object but in Reality a wall is just an structural object too.

I think it is good that we have the option to decide if a wall should be a structural wall, from which such an analytical model can be created, or just an "architectural" wall that is dividing the rooms. I believe IFC also allows such logic.