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This thread is not about which is the best calculator.

Its about programming the HP35s with all its limitations.

I don't doubt that an HP70, and HP50, an HP426-and-a-half or a Cray Bitz would be better but I don't have any of those and I'm not planning to buy one. I have an HP35s and I am interested in programs for THIS model. Please everyone, don't bang on about how much better it would be to use a different one!

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STRUCTURAL FRAME ANALYSIS FOR AN HP35s

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I would very much to write such a program.

But I can't.

(Explained below).

The HP35s seems to be limited to 26 direct and 100 indirect storage locations, which limits the maximum size of structure. I've just looked at this a little more closely and I estimate that the calculator could possible solve a structure with eg 4 lines of columns and 3 upper storeys, which is 16 nodes and 21 members.

This would be a seriously useful tool for structural engineers.

It would be possible only by three tricks.

(1)Use a simple member numbering notation

that eliminates node numbering.

(2)Assuming infnite axial stiffness

and analysing only shears and moments.

(3)Storing only the equations halfbandwidth.

This would eliminate lengthy input routines (making for a short program). It would also need a clever equation solver with a simple algorithm to retrieve stiffness matrix terms from packed halfbandwidth storage. The solver would also need to solve the equations in-situ, by which I mean that the original coefficients become gradually over-written by the solution, and to do this entirely in the half bandwidth of a banded symmetrical matrix. Such solvers do exist in eg Fortran or c but would need porting to HP35s machine code (not hard to do).

All the above seems very tempting... but just when can I ever find the time to do it? Answer: I can't!

Would anyone else be interested in having a go at it? Probably we need a structural or aeronautical engineer who enjoys numerical modelling to tackle it. I would be happy to help with suggestions - in particular with the member numbering convention referred to above, which facilitates direct assembly of stiffness equations.

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John