Gauss point location

[BigBanana]

Hi,

I have a simple model of cantilever beam under tip horizontal load, which consists of two displacement-based beam elements. Each displacement-based beam elements have two integration points and following Gauss-Legendre quadrature rule. The location of Gauss points should be inside the beam element (v.s. force-based beam follows Gauss-Lobatto rules that Gauss points are at the beam ends). The beam elements are prismatic and the analysis is elastic. I provided my tcl code below for reference.

Code: Select all

wipe
model basic -ndm 2 -ndf 3 

node 1 0 0 -mass 1.0 1.0 1.0
node 2 0 150 -mass 1.0 1.0 1.0
node 3 0 300 -mass 1.0 1.0 1.0

fix 1 1 1 1 
fix 2 0 0 0
fix 3 0 0 0

uniaxialMaterial Elastic 1 29000

section Fiber 1 {
   patch rect 1 1000 2 -25.0 -10.0 25.0 10.0
}

geomTransf Linear 1

element dispBeamColumn    1    1     2     2      1        1
element dispBeamColumn    2   2    3     2       1       1

timeSeries Linear 1

pattern Plain    1         1 {
   load 3 2.0 0.0 0.0
}

 recorder mpco "SKTO_elastic.mpco" \
 -N displacement rotation reactionForce reactionMoment \
 -E force stress strain material.force material.stress material.strain \
 section.force section.stress section.strain section.fiber.stress section.fiber.strain


constraints Penalty 1e15 1e15
numberer Plain
system BandGeneral
test NormDispIncr 1.0e-8 100
algorithm Newton
integrator LoadControl 0.01
analysis Static

analyze 100

When I visulize the result in STKO post-processor, the Gausspoint plot shows the Gauss points are located at beam ends, see the screenshot attached.
And when I plot the beam bending moment diagram, you can see the bending moment is dis-continuous between two elements. I output the bending moments at end of beam element and noticed they equal to the moment value at Gauss points. However, as I mentioned above, the Gauss point for displacement-based element should be inside the element.

Any comments are welcomed

[kesavapraba]

Indeed, you are correct in noting that the integration points are displayed at the ends of the beam. In the current scenario, STKO relies on OpenSees to gather information about integration points. However, due to the absence of standardized rules for outputting the location of integration points in OpenSees, STKO assumes that they are situated at the ends of the beam. We acknowledge this challenge and are actively working on identifying a workaround. Subsequently, this workaround will be incorporated in future releases of the STKO software. Thank you.