[Plugin] Finite Element Analysis (FEA) - Spring-mass model

qpik · 17 Dec 2009, 09:29

Since I'm an architect I've been looking for an easy way to incorporate FEA into SU. This would add a completely new dimension to design in SU.

After browsing through some books I found the math a bit to hard so I decided to start off with a simple spring-mass model (to be exact it's not 100% real, instead of a=F/m, s~F/m)

simple_springs.rb
Here is a video example:
[flash=425,344:13mjw25i]http://www.youtube.com/v/ojtHu1yZSUQ&hl=pl_PL&fs=1&rel=0[/flash:13mjw25i]

I hope someone with strong mathematical background would take this on or help me to go on.
What about SketchyPhysics? I tried it couple of times but I'm not sure it's suitable for this purpose.

Kuba

remus · 17 Dec 2009, 11:02

Ooooh, this looks very interesting. I'll have a look through the code later today and see if i can wrap my puny brain around it

daiku · 17 Dec 2009, 22:34

Many Timber Framers use Sketchup to design their frames, and having an FEA plugin would be an awesome addition. CB.

qpik · 18 Dec 2009, 07:52

I wonder. Maybe instead of going math intensive subdivide a model into an array of virtual springs. Transforming them should be faster than the actual model. What do you think?

tfdesign · 18 Dec 2009, 11:34

I did a bit of FEA in my engineering degree, using ANSYS- but it was mighty complex. I think you are taking on a huge project here!

There is decent FEA software around, and perhaps it would be better to develop a plugin that would communicate between SU and FEA, rather than trying to do stuff from scratch? I was for a start, really impressed with an application called GMSH, but it may be too complex for architects- more for engineers, but at least SU could be used as the CAD modeller for GMSH? Perhaps the physicists (you need these guys, more than mathematicians!) at GMSH could also help with basic physics problems.

For further reading, I'd recommend "Structural Timber Design" by Abdy Kermani, published by Blackwell Science Ltd (available from all RIBA bookshops ISBN: 0-632-05091-8). This book covers all the properties of timber, and their types, as well as the complex formulae needed to solve various problems- like how strong timber frame walls should be, to withstand wind pressures from various sides, and the calculations needed to have just the right amount of wood, to withstand those pressures, at the most value for money (sustainable technology), and the all the maths needed to work it all out. It's not a 'cheap' book, but it's all in there, and best of all, to British Standards (BS 5268: Pt2: 1996). There is also a bit of info in there, on the software called MathCAD.

MALAISE · 21 Dec 2009, 17:29

This is a real extension to SketchUp. Hopefully will this thread growing up.
Thanks Qpik

MALAISE

MALAISE · 24 Dec 2009, 15:43

Drzen Dobre Qpik

Would you share with us some drafty file.skp; At this moment, I don't see how to use the plugin.
Thanks a lot.

MALAISE

mitcorb · 24 Dec 2009, 17:14

I am interested to see more on this.

brichins · 28 Dec 2009, 20:57

I'm currently doing my masters in civil engineering, and know a fair amount about FEA. I'd have to agree that the best approach may be to try communicating between SU and an existing program, perhaps Matlab, OpenSees or something similar.

That being said, I've wished for something like this in SketchUp more than once. I'd be somewhat interested in looking at this with you; I'm not particularly strong on programming SketchUp, but I think I could help a bit with the math. I'm not sure how powerful/complicated you want to make this; I don't think SU has the math power for anything too intense.

glro · 3 Jan 2010, 20:49

Hello,

i wrote a finite element structural analysis software many years ago

using the displacements method, building a rigidity matrix, then solving a linear system of equations...

i wrote it basic, only for 2d structures, and it took me much more lines of code than what i see in your ruby file

either Ruby is really amazing, either you are missing something...

i can't tell you, because i don't understand ruby code

but i did try to model a half spherical structure using my FEA software, and the deformation is not at all the one you show in your AVI file

Your idea is great, but i am not sure Sketchup is the best environment to develop it

deformation of a half spherical structure using acord bat from Itech

muchado · 9 Jan 2010, 18:04

I am also interested in this. I am a structural engineer and am trying to see how I could use Sketchup to build structural models. Typically, this would involve creating models of 1D and 2D elements, which would be interpreted as beams & columns and walls and floors. I would be interested in hearing if anyone else has added attributes to existing 1D and 2D entities in Sketchup, and how to do it. Specifically I would be looking to add orientation, sectional area and flexural stiffness to 1D entities, and thickness to 2D entities.

If you are looking for a structural solver, then you may want to look at OpenSees (http://opensees.berkeley.edu), which is open source from the University of California, Berkeley. It is intended for seismic analysis, but would probably do what you want. OpenSees might be best if you are looking to model large displacements of frame structures, as you appear to be wanting to do, but it would take time to get familiar with the program, especially if you are not already familiar with structural FE analysis.

If you are in academia, you could get free copies of GSA from Oasys (http://www.oasys-software.com). It has a good DXF import/export and also a COM interface. Gmsh has a free solver called GetDP for shell FE analysis which might also fit the bill.

Other options would implementing solvers yourself, but this could be quite time-consuming, whether by matrix FE analysis (implicit), dynamic relaxation or explicit FE analysis, which seems to be the logical extension of your approach. You would still need to define section properties first, though, and this will require some sort of adding attributes, either to the entities themselves, or by reference to layers - i.e. each entity in a certain layer would be assigned a certain section property.

GrojGuy · 27 Aug 2010, 08:53

I realize this thread is a bit stale, but I am very interested in this as well. After becoming familiar with some of the commercial products available, and seeing what limited modeling interfaces they provide, I definitely think SU would be a great modeling tool to use as the "front-end" for a structural FEA tool. The biggest weakness that I see with many of these commercial products out there is that they try to re-invent the wheel with their front-end modeling interface, and most of the time fail miserably. In one case I actually modeled a project in SU, then exported/imported it as DXF into the structural analysis program.

The thing is, I don't think the FEA mathematics is any big secret. Complex, yes, but secret, no. Instead, I think it's more a matter of the value-added features like automatic member (re)design based on analysis results, visual analysis reporting/diagrams, regulatory code compliance checking, things like that. It is a fairly complex and involved arena, no question about it.

In the same way that the commercial structural analysis packages should not have re-invented the 3D modeler wheel, I agree with what has already been said, no reason to re-invent the wheel if a suitable FEA engine can be found and integrated with SU via Ruby scripting.

Has anyone hear ever looked at LISA? http://www.lisa-fet.com/ This really looks like it could fit the bill for static structural analysis. What is interesting is that it also seems to do other things like hydraulics, which could be interesting for wind loading. OpenSees also looks interesting, that could perhaps be used for the non-linear/dynamic (e.g.) siesmic side of things.

pilou · 29 Aug 2010, 22:16

A free one: Z88 (not for SU)

glro · 1 Dec 2010, 19:01

It seems that somebody is trying to write something similar

http://sites.google.com/site/teclait/home

the structural part is still not available... but it will probably include some finite elements program...

@qpik said:

Since I'm an architect I've been looking for an easy way to incorporate FEA into SU. This would add a completely new dimension to design in SU.

After browsing through some books I found the math a bit to hard so I decided to start off with a simple spring-mass model (to be exact it's not 100% real, instead of a=F/m, s~F/m)

[attachment=0:2f7ju4i2]simple_springs.rb[/attachment:2f7ju4i2]
Here is a video example:
[flash=425,344:2f7ju4i2]http://www.youtube.com/v/ojtHu1yZSUQ&hl=pl_PL&fs=1&rel=0[/flash:2f7ju4i2]

I hope someone with strong mathematical background would take this on or help me to go on.
What about SketchyPhysics? I tried it couple of times but I'm not sure it's suitable for this purpose.

Kuba

bomastudio · 2 Dec 2010, 12:24

@glro said:

It seems that somebody is trying to write something similar

http://sites.google.com/site/teclait/home

the structural part is still not available... but it will probably include some finite elements program...

Yes, of course ... I'm a structural engineer .... I want to extend TECLA (see the project home

http://sites.google.com/site/teclait/home

to build a FEM software based on SU. Ad the moment I'm developing the Architectural modulus (that will be, with some changes, the Pre_processor).
I'm looking for some FEM software open-source and find some:

Calculix, GmsH, FreeFEM++ but nothing in ruby!!! Someone has news?

glro · 6 Dec 2010, 16:19

@bomastudio said:

@glro said:

It seems that somebody is trying to write something similar

http://sites.google.com/site/teclait/home

the structural part is still not available... but it will probably include some finite elements program...

Yes, of course ... I'm a structural engineer .... I want to extend TECLA (see the project home

http://sites.google.com/site/teclait/home

to build a FEM software based on SU. Ad the moment I'm developing the Architectural modulus (that will be, with some changes, the Pre_processor).
I'm looking for some FEM software open-source and find some:

Calculix, GmsH, FreeFEM++ but nothing in ruby!!! Someone has news?

i am afraid you won't find anything in Ruby; the language has not been used for structural analysis, as far as i know

but it might not be a problem; you could link a program in Ruby, to another program in another language, by exchanging information through text files

i did it between Ruby and Basic, and it worked...

bomastudio · 25 Jan 2011, 08:49

@unknownuser said:

i am afraid you won't find anything in Ruby; the language has not been used for structural analysis, as far as i know
but it might not be a problem; you could link a program in Ruby, to another program in another language, by exchanging information through text files
i did it between Ruby and Basic, and it worked...

yes, it could be done....

But, as I'm tryng to develop a FEM engine by myself (I wrote a 2D fem program in MATLAB at University some years ago...), I need a solid matrix/linear algebra library in Ruby. Now the aim is to use it inside SU both in Windows (& Linux+wine) and OSX. I found Matrix.rb but I don't like it ... any suggestion and how use with SU?

tjlahey · 20 Feb 2011, 09:01

I've just started to use SketchUp, but I have a lot of experience in writing FEA code. One thought I had was to link SketchUp with FEMhub which is being developed with a web-based interface so it could be used in a web view via a plugin. They are working on 1D, 2D, and 3D solvers. Their web interface is a bit much for a plug-in, but it's probably a good place to start.

sbolin · 8 May 2011, 07:25

@bomastudio said:

@glro said:

It seems that somebody is trying to write something similar

http://sites.google.com/site/teclait/home

the structural part is still not available... but it will probably include some finite elements program...

Yes, of course ... I'm a structural engineer .... I want to extend TECLA (see the project home

http://sites.google.com/site/teclait/home

to build a FEM software based on SU. Ad the moment I'm developing the Architectural modulus (that will be, with some changes, the Pre_processor).
I'm looking for some FEM software open-source and find some:

Calculix, GmsH, FreeFEM++ but nothing in ruby!!! Someone has news?

Very interesting idea to have a FEA ruby. I'll be watching to see if anything develops on that front. I sort of agree with the general idea that it may be better to write a translator from SU to an existing FE program, but if it can be done within SU all the better. It does seem like a huge amount of work, though

bomastudio · 2 Jul 2012, 09:24

Update: I found (thanks to Google!!) this project

Frame3DD - Static and Dynamic Structural Analysis of 2D and 3D Frames

Free software for static and dynamic analysis of 3D moment-resisting elastic frames and trusses. Written in ANSI C. Source code includes: frame analysis with elastic and geometric stiffness, LDL' decomposition, LU decomposition, Newton-Raphson iteration, sub-space iteration, Stodola iteration, static condensation, Guyan reduction, dynamic condensation, Matlab support and spreadsheet support. Graphical output and mode shape animation via Gnuplot.

(frame3dd.sourceforge.net)

released under GPL for Linux (wow!!!), Mac and Windows.
It seems very good...... now I'm asking to the author if Frame3DD supports rigid link to model unaligned elements (colums and beams as in the following image