Dear Atena community

I am currently working with 1D-Beam elements to simplify the simulation of a big structure. However i stumbled about a problem when looking at the cutting forces (Element Nodes : M N Q Beam : N/MY) when using 2IPs along the beam elements longitudinal axis. The displayed cutting-forces are clearly wrong in my opinion and do not represent the forces acting on the beam. However the behaviour of the beam and the calculated stresses and strains at the elements cross-sectional IPs are correct!

When the number of integration points in the longitudinal axis is changed to 3 or more the cutting forces are displayed correctly and coincide with the stresses displayed at the integration points of the cross section.

I also looked up the ATENA Example library and found a similar one in "1Dbeam_middleforced.ccs" where also 4 IPs for the beam elements longitudinal axis are used. When i change this value to 2 the same effect happens.

I am now wondering if i understand or model something wrong as the atena-input file documentation recommends the use of 2 IPs along the beams axis and just increase this for strong material nonlinearity.

Or is this a little bug in atena because i said the behaviour is calculated correctly in my opinion but just the postprocessing does not give the corresponding cutting forces for 2IPs.

Here is a link to a working example to test in case someone is interested:
https://www.dropbox.com/sh/3b3g2hw7m8wk … RbJba?dl=0