Generate Tapered BEAM Properties from Patran

Question

This is in response to Tech Article ID KB8012044. I have some questions in order to understand this.

What does the station distances represents?

Do they need to match with my Grid Location?

Suppose I have cBeam ( ONE bar2 element) between two grid points (GA and GB) (10 units apart) and I need to create a tapered beam

Will my input be

Station distance 0.0 10.0

Cross Section Area 1.0 2.0

Inertia 1,1 10

Inertia 2,2 10

Inertia 1,2 20

Torsional Constant 18

Does the above input means that at grid GA (station 0.0) an area of 1 with the above properties be created and at grid GB (station 10.0) an area of 2 with above properties be created?

Arthur Hickson · Accepted Answer

Yes - 50%constant 50% tapered area. This is a rather fictitious example as changing the areas and not having the Inertias change too is most unlikely.

Patran will only show the "cross section" using the end data - not the intermediate position section data.

There is no need for multiple station locations. Think of it as a historical capability that was required back in the earliest days of FE when the size of the matrices(DOFs) you were solving was severely restricted by the computer power available. If you are introducing no external forces(constraints) at the intermediate positions then you do not need to model them to understand the force/displacement relationship (stiffness) between the end points. The ability to model a beam with changing section properties with just two grid points is a nice way to keep the number of DOFs in the model small. You can also think of this in a similar way to the use of "super elements", where you take a FE model and reduce its stiffness matrix down so it is only referencing the grids (DOFs) that connect it to other parts of a larger structure.

So don't worry about wondering why you would want to use intermediate stations, you probably would not, these days you would just have grid points at the intermediate locations and multiple elements. The complexities of using multiple station locations probably outweighs any possible gain, these days computers are so powerful that I would not contemplate using this quaint feature.

Edwin may well have additional input, and this is of course my personal perspective.