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Matrix analysis using spreadsheets.[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaint(--nospam--at)seaint.org
- Subject: Matrix analysis using spreadsheets.
- From: G Vishwanath <gvshwnth(--nospam--at)yahoo.com>
- Date: Fri, 20 Jun 2003 04:28:18 -0700 (PDT)
Yes, it is possible. I did it about 7 years ago. I did it for truss structures but the same could be done for rigid jointed plane frame or skeletal space structures also. I had to analyse a number of latticed trestle structures that supported conveyor galleries. The heights, base widths, top widths varied considerably. The member patterns also varied but could be grouped into a few basic types. I got tired of inputing joint coordinates and member information and loading information for each of the innumerable types of trestles into STAAD which was our Analysis tool at that time. It was then that the idea of using a spreadsheet struck me. Basically there were about three to four standard trestle shapes we used in that project and I "parametrized" them in the spreadsheet. The inputs were the width of the trestles at the top and bottom, number of vertical bracing panels and the height. That took care of geometry and topology. By specifying the properties of the column and the brace member, in each panel, the member property information was ready. The loading information was the point loads delivered at the top of the trestle from the conveyor gallery (vertical loads due to DL and LL and horizontal due to wind) Thus with just a few numbers input into the appropriate cells, I had enough information to generate the joint coordinates, member connectivity information, member property and loading information that the analysis program needs to proceed. I wrote simple formulas to generate the joint coordinates and member informaton from this basic information. This was neatly formatted and tabulated in the sheet. And now for analyis. It was simple. I already had the complete text of a truss analysis program in Basic which I had been using in the late seventies and early eighties before the advent of personal computers. I simply copied the entire text of this program into the VBA editor and created a "Mega Macro". VBA can read almost all of good old GW Basic and Quick Basic source code. I had to modify only the input and output statements of the original source code. The Read/Input statements were replaced by giving reference to VBA statements that read data from cells and stored them in the variable names used by the matrix analysis program. The print statements of the program were replaced by the the relevant VBA statments that transferred the values of the output variables to predetermined cells neatly arranged in a designated area of the spreadsheet. The spread sheet worked like a charm. I did hundreds of trestles over a period of two years using this simple spreadsheet technique while previously I had used Staad to write long data files for each of these standard shaped truss structures. I could do "what if" easily and conveniently. I had forgotton about it and I no longer do analysis of structures now. But your mail brought back fond memories of highly satisfying moments which I had enjoyed when I finally got the the spread sheet working. I hope this helps you to take this idea further and even better it. I don't know if I can locate this spreadsheet now. It may still be gathering dust be on some old floppy disk or CD rom on which I have been backing up my hard disk. I don't have it on my hard disk now. The disk crashed some time back and I lost everything. I need to rummage through my cd roms and floppy disks and if I am lucky, I may chance upon it somewhere. I will consider looking for it and even sharing it if anyone is genuinely interested. While it may not be usable directly now, after a lapse of so much time, it could serve as a starting point for any one who wishes to take this further. Modifying the formulas in the sheet will make it adapt to another type of truss configuration. But the macro itself will need total rewriting if the idea is to be extended to plane or space frames. Mail me privately if you want me to share this sheet with you. Regards G Vishwanath Bangalore India __________________________________ Do you Yahoo!? SBC Yahoo! DSL - Now only $29.95 per month! http://sbc.yahoo.com ******* ****** ******* ******** ******* ******* ******* *** * Read list FAQ at: http://www.seaint.org/list_FAQ.asp * * This email was sent to you via Structural Engineers * Association of Southern California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, please go to: * * http://www.seaint.org/sealist1.asp * * Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you * send to the list is public domain and may be re-posted * without your permission. Make sure you visit our web * site at: http://www.seaint.org ******* ****** ****** ****** ******* ****** ****** ********
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