Rigid Strut

[B.L.Smith]

As you know rigid strut is a support without gap which it can withstand tension and compression, thus the pipe which attached to it, can rotate about the pin attached to the structure.
If two rigid struts attach to a point of a pipe, this point will not move in any direction. But in most documents which I've seen on net, this kind of support call “guide” or “directional Stop”; For instance in Fig.6-4 attached(From samsung compressor & turbine piping design standard), Y direction is mentioned movement direction, but the pipe cannot move in Y direction because, two rigid strut do not have any gap.

 

[pennpiper]

Brad,
You wrote "the pipe cannot move in Y direction"

That may or may not be true.
- What is dimension "L"
- What are the individual components of the two struts(in detail)?
- What size is the pipe?
- What are the two struts attached to (besides the pipe)?

prognosis: Lead or Lag

 

[Compositepro]

It all depends on the tolerances you are interested in. The "rigid" struts are far more rigid in their axial direction than in restraining movement perpendicular to the axial.

 

[C2it]

Ref. the left side diagram ...

Realistically the only direction that should be considered fixed is the Z translation, and if these are rigid struts, one is redundant.

Given that pipe rotations tend to be fractions of a degree, the two struts would not in the real world resist rotation in any direction.

Likewise X and Y translations would only be restrained until local flexibilities came into play.

 

[B.L.Smith]

Reply to Pennpiper: Movement in any direction is independent of those parameters which you mentioned; Because pipe size may be varied and the structures which two struts attached are rigid theoretically.

Reply to Compositepro: Rigid strut is a support without any gap, thus movement of the pipe in perpendicular of strut for using of "two" rigid struts is impossible definitely.

Reply to C2it: Two rigid struts allow rotation around point "A" in fig 6-4, but this point could not move in any direction.

 

[C2it]

BradSmith,

You need to think about the practical aspects of local flexibility and exactly what a directional restraint is meant to do.

Let's put it this way. If you designed a restraint such as I referred to in order to resist movement in any direction other than the Z direction, you would not last long in my firm.