Frame Analysis

[rjmacpherson]

Morning all,

I am currently running two models in Patran/Nastran which are to represent a simple frame structure. In the first model, I use two beam elements which have a common node. Each free end I have restrained in all 6DOF and the joint node is restricted in 3, Z Translation. I am using the default coordinate system. For each beam, they have the same rectangular cross section and this is input using the beam properties area. I apply a XY load to the joint node and run the analysis. When I get the results of this, I get reactions at each of the fully fixed nodes, and bending moments in each of the members in plane 1 only.

The second model is similar however instead of rectanular sections, has L Sections. When I run the analysis, as before I get bending moments in plane 1, but now also in plane 2.

Am I now getting BM in Plane 2 as the sections are non-symmetrical? Also if I am using the default coordinate system, how do I tell what is Plane 1 and Plane 2?

Any help would be greatly appreciated!

Many thanks,

Rich

 

[corus]

Plane 1 is obviously the XY plane from your 1st model. In the 2nd case the deflection of a non-symmetric beam is away from the axis. Look in the Structural Steel Designer's Handbook for examples.

Tata

 

[rb1957]

read the manual ... in my experience beam orientations are frequently confused.

i would also make a simple model to test what i think i understand from the manual.