spreadsheet for truss design-request for algorithm 4

[IJR]

Pals

I want to write a VBA or a spreadsheet that calculates bar forces in a statically determinate truss of any configuration. I do a lot of truss calculations and a spreadsheet would be handy

Anyone knows a good algorithm or a reference

respects
IJR

 

[GregLocock]

Bowes notation

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[yakpol]

IJR,

What structural software is in your possesion? Does it allow text file input? Use excel to pre-process input and to post-process the results of commercial program. Writing your own solver even for statically determined structure will take lots of efforts, much more than you wish to spend.

yakpol

 

[UcfSE]

I've done what you're asking for frame analysis using MATLAB. As yakpol says, even with no GUI and a lot of user-unfriendly input requirements, it was an incredible amount of effort.

I don't know of a free solver from the net. You can write one yourself using matrix analysis methods.

 

[rb1957]

maybe a cheap fe program would do it for you ?

 

[IFRs]

I used to use a program called Imaes 3D which would accept ASCII data input created from a VB program I wrote that solicited a configuration for analysis. The output was also ASCII and easily post-processed. Same for an old version of SAP4. Good luck!

 

[Dinosaur]

If your geometry is fairly similar each time, then I would use Excel or Mathcad or something and make my own using their matrix inversion routines. If the geometry changes radically from one problem to another, I might have STADD or something. This can be upgraded by creating your input file with the help of Excel to compute your geometry and stuff. I once used these methods to analyze OH sign structures. Good Luck.

 

[PJHudson]

Matrix Analysis of Structures by Weaver and Gere has a nice fortran routine. I translated the plane frame program into visual basic for a school project. It runs inside excel. I made a lot of changes, additions and (improvements?). I still use it at work. It is very quick to set up frames. I wish I could release it under something like a GNU public license, maybe someone would help improve it, 3-d plates etc., but I am unsure of copyright issues. I might try to rewrite the core with a public domain solver etc.

I also saw a simple plane frame and truss program by an Australian professor. It works fine with a relatively slow gaussian solver. I will look for the author if anyone is interested.

 

[IJR]

PJHudson

Go on if possible to get us some authors

respects
IJR

 

[MiketheEngineer]

I actaully wrote that program over thirty years ago using a matrix solution. Got a copy of a college handbook and just followed it. Worked great.

That software evolved into a leading package used by one of the largest truss plate suplliers around.

It took a couple of hundred hours getting it to work and adding a bunch of enchancements to make the input much more user friendly.

I think you could find some cheap software on the Net that will solve your problem or spend a few thousand and buy a ready made package.

Good Luck

 

[PJHudson]

Dr. Andrew Deeks of the University of Western Australia used to have a few Excel spreadsheets for truss and frame analysis using visual basic macros on his class website. I couldn't find them when I looked the other day. He seems to be on sabatical in England at the moment. If someone asks, you never know, he might be willing to send a copy.

I won't post my spreadsheet as I'm uncertain about software copyright issues. Does anyone know how to judge when something is altered enough to no longer be a copyright infringement? Also does any know of an open source matrix analysis code that could be translated to visual basic to run inside Excel? I have seen a few open source programs out there but they are a bit more involved than I have time to deal with.

 

[KiwiMace]

Try looking for this book:

Numerical Methods for Engineers. Griffiths and Smith
Blackwell Scientific Publications.

Covers Linear Algebra and the matrix operations/solutions you requested, non-linear, eigenvalue, interpolation, integration, ODEs and PDEs - all with Fortran 77 subroutines for you to convert to VBA.

This was a third year eng school text which I found quite usable and useful later on.

 

[PJHudson]

Numerical Methods for Engineers. Griffiths and Smith

I think I read some of this book in school. If it is the book I think I used it was very helpful. I don't think I could distribute a program using the code legally though, even though it is in the book. Doesn't redistribution of a published work constitute copyright infringement?

I am leaning towards a federally written bit of software, BLAS or TNT that is in the public domain, but I haven't found more than the solver yet. Otherwise I might look into using/modifying a GNU GPL license program like OOFEM. Has anyone worked on or is anyone interested in developing a GPL finite element package oriented towards civil engineering? Seems a bit daunting but it might be fun.