equations for a hellicoidal stringer-any? 2

[IJR]

Pals

I am looking for equations to determine at least reactions for a simply supported hellicoidal beam (similar to a stringer in hellicoidal stairs) supporting uniform distributed loads.

any literature reference will do.

respects
ijr

 

[ishvaaag]

http://www.ieindia.org/publish/cv/0205/feb05cv9.pdf

https://workshop.cvut.cz/2007/download.php?id=STA078

http://nels.nii.ac.jp/els/110003881...der_no=&ppv_type=0&lang_sw=&no=1255523665&cp=

http://scitation.aip.org/getabs/ser...00132000002000312000001&idtype=cvips&gifs=yes

http://www.springerlink.com/content/pt44tx13428t2884/

http://www.springerlink.com/content/w2r04p0q31336020/

 

[BAretired]

A helicoidal beam cannot be simply supported or it would be unstable. If the minimum number of reactions are used, the structure is statically determinate, otherwise it is indeterminate.

BA

 

[IJR]

BA retired

how determinate? can you please elaborate a bit

respects

ijr

 

[racookpe1978]

BA retired

how determinate? can you please elaborate a bit

---
How do you determinate?

Well you bolt it down real good at one end, then you determinate where de holes are at the other end, then you drill all de holes in all de pieces so dey all fit. 8<)

 

[IJR]

racookpe1978

you got me wrong. I mean how can you make a space system determinate when you need 6 degrees of freedom

respects
ijr

 

[BAretired]

You do not need 6 degrees of freedom. You have, potentially 12 degrees of freedom, assuming two support points. There are 6 at each point of support, namely Fx. Fy, Fz and Mx, My and Mz.

You stipulated the loads were uniformly distributed, and I interpreted that to mean gravitational, i.e. parallel to the Z axis. The support points could be, for example a hinge and roller, eliminating the Fx and Fy components and leaving us with two Fz components. But that would be unstable as the applied load will likely not align with the two vertical reactions. This may be resolved in several ways.

One is to add another vertical reaction which does not align with the first two. In this way, the beam becomes statically determinate and can be analyzed for moments and stresses at every cross section.

Another method is to provide a restraint in the form of a moment whose vector aligns with the two vertical reactions. Again, this makes the structure both stable and statically determinate.

Or, you could provide a horizontal reaction above or below the support points. And there are numerous other methods which shall be left to the imagination of the reader.

What you cannot do is to build a simply supported helicoidal beam.

BA