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Matrix analysis using spreadsheets.

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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


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