Hi all,
Is there anyway please to connect two intersect meshs, I tried join breps before meshing but didn’t work
Model 3Rhino.3dm (690.5 KB)
mesh Scala chiociola.gh (7.4 KB)
Thank you in advance
not possible
is there any alternative way to do that?
Use join brep and create mesh from brep. But for breps to join they have to share edges. You can use mesh boolean too, but for that meshes have to be closed (have thickness)
@Brad_Shipton Yes exactly I need it for analysis. I know that the geometry is not perfect but its ok.
While your geometry might be okay, that is the reason you cannot get them to join. There is no mathematical relationship between any of the lines or points, so it is impossible to solve. If you fix the geometry you can solve this.
A few questions:
- Are the actual shapes circular? This looks like a typical circular staircase, so I expect there are some very simple relationships like radii, and rise/run.
- Can your analysis software deal with 3D mesh shapes? We use SAP2000 and it will only work with planar meshes. You will need to consider this because that simplification will lead to disconnects in the analysis model.
No no, the breps intersect in all the path.
we also use Sap2000, I’ve already did this mesh with triangular mesh thanks to a KARAMBA3D component and it’s works fine in sap2000 without any disconnections. But we need a quad mesh not triangular, maybe triangular just at the hard edges.
I understand they intersect, but there is no mathematical relationships so GH cannot solve your problem. Unless you have access to software with better mesh generation like Abaqus, ANSYS, Diana or others, this will take a lot of manual effort to avoid poorly shaped meshes.
I suspect the data here came from a 3D scan. Maybe a historic building?? Many times we need to simplfiy the problem for analysis. In the attached I examined your dimensions and found the max/min sizes. I re-modelled the surfaces in the shapes that might work better for analysis. You can add/delete whatever you want. The intent was to show a different method to solve the problem. I did not include the landings, but you should get the basic idea. The approach is to remodel the problem using the meshes you require for analysis. This grasshopper can solve. The script is very messy, but I do not have time to improve it.
mesh Scala chiociola-BRAD.gh (32.8 KB)
Thanks a lot @Brad_Shipton for your time. I am thinking like this because I did the mesh with just one component from KARAMBA3D, all the vertices are connected that’s why I think maybe a way to do quasd mesh
You will need to run the analysis and see. Generally small slivers or extremely small angles cause problems with the mesh. Once you run the analysis you will see. With this type of automation you can easily test your mesh sensitivity. You need to look for odd stress spikes, breaks in the mesh or other oddities. Depending on your goal with all of this, that may or may not be important. When we work on projects like this our goal is to build the structure or offer advice if it needs fixing.
Given the tread shape you will have triangles, but the SAP automatic mesh tool will likely do a good job dealing with that so long as you do not have a lot of extra nodes that cause the mesh tool to try to add more triangles. The rest of the parts would largely be quad shaped if you re-build the stair.
After posting this I went back to the file and investigated your geometry closer by finding some best fit curves and the intersection at the middle of the treads. I can tell the shapes are not coming from scan data given how exact the tread rise/run is. Other than the rise of the bottom tread, your dimensions are all quite precise. For some reason your outer and inner radii are inconsistent. This is not how it can be built. To build something like this using modern methods means the geometry needs to be much better so the trades do not spend endless time on site fitting parts or making unique forms. Labor was very cheap eons ago, so if this was a historic stair I might understand the geometry.
One advantage of improving your geometry is you can create section cuts so SAP will find your design forces. Below is an example of how I do this for some wall panels. GH can create hundreds of section cuts easily and if your geometry has some logic you can create a diagram like this.
I have never used Karamba, so I do not know about its mesh tools. The mesh posted looks quite good except where you have overhangs. We export data from GH to SAP using Geometry Gym.