Calculation Points in Steel Design

[dieter]

Hi, I would like to know how the "Calculation points" are considered in the Steel Design > Calculations dialog > Configuration. One has the possibility to indicate the number of points and optionally some characteristic points. By default only "3" is indicated. Help file indicates that "the points are evenly distributed along a member length". But I still assume that RSA takes the max set of forces into account. What is the use than of indicating characteristic points. Or am I wrong and should I always indicate the characteristic points for max Fx, max Fy, ... to be sure that all max forces are taken into account? Please, can you assist me on this. Thx. Best regards, Dieter Vermeulen Product Manager AEC i-Theses bvba Belgium

[Rafal.Gaweda]

---

Dieter,

Hi, I would like to know how the "Calculation points" are considered in the Steel Design > Calculations dialog > Configuration. One has the possibility to indicate the number of points and optionally some characteristic points. By default only "3" is indicated. Help file indicates that "the points are evenly distributed along a member length".

Yes, it is like that.

But I still assume that RSA takes the max set of forces into account. What is the use than of indicating characteristic points.

http://forums.autodesk.com/t5/Autodesk-Robot-Structural/Steel-design/m-p/3340849/highlight/true#M288...

Or am I wrong and should I always indicate the characteristic points for max Fx, max Fy, ... to be sure that all max forces are taken into account?

This must be indicated by user.

[dieter]

So, what about the next scenario:

- the Calculation points are set to 3, so a bar of 3 m is diveded in 2 x 1,5 m to have start, mid and endpoint.

- the max My is at 1 m from startpoint of the bar

How am I sure that RSA takes the value of My,max @ 1m into account and not the ones calculated at the three points, which are less?

So again,

Or am I wrong and should I always indicate the characteristic points for max Fx, max Fy, ... to be sure that all max forces are taken into account?

[Rafal.Gaweda · Accepted solution]

So, what about the next scenario:

- the Calculation points are set to 3, so a bar of 3 m is diveded in 2 x 1,5 m to have start, mid and endpoint.

- the max My is at 1 m from startpoint of the bar

How am I sure that RSA takes the value of My,max @ 1m into account and not the ones calculated at the three points, which are less?

Activate addidional check for extreme My.

[dieter]

So that means, by default, RSA does not look at the max moment, axial force and ... for making the code verification.

The user has to check those checkboxes each time then?

[Rafal.Gaweda]

So that means, by default, RSA does not look at the max moment, axial force and ... for making the code verification.

The user has to check those checkboxes each time then?

Yes.

The reason was the time of calculations for large models, large numer of combinations, especialy with seismic

[dieter]

Strange. In next screen capture, I use 3 points and didn't check the characteristic points checkbox.

Still, RSA takes into account the max moment, which is at 0,135 * L of the bar, which is also indicated in the Point/Coordinate field of the Results dialog, which is correct, and - don't get me wrong - is great !

Still I don't understand the goal of characteristic points than. With the explanantion of above answers, I would have expected in this case, the maximal moment My,Ed would be the one from the middle of the bar.

Can you clarify this please?

[Artur.Kosakowski · Accepted solution]

Dieter,

Looking at the diagram I assume that you defined a bar force at this point. If you look at it definition dialog you can see that by default the generation of a calculation node in the force location is switched on. This point 'splits' the bar into two calculation elements and check is done in 3 points for each of these elements. By the way this is the reason why this check box (and this functionality) has been introduced to the bar force definition