Strand7 Beam-columns with applied moment and axial load
Strand7 Beam-columns with applied moment and axial load
(OP)
Hi,
I am trying to model a beam-column in Strand7 that is simply supported, and has applied compressive axial load and equal and opposite end moments at each end.
After I run the linear static analysis I get the warning 6 (Node force/moment component at node xxxx is ignored) for each of the four applied loads. So the analysis is not considering any of the loads.
Does anyone know why this is happening and how to fix it?
Many thanks.
I am trying to model a beam-column in Strand7 that is simply supported, and has applied compressive axial load and equal and opposite end moments at each end.
After I run the linear static analysis I get the warning 6 (Node force/moment component at node xxxx is ignored) for each of the four applied loads. So the analysis is not considering any of the loads.
Does anyone know why this is happening and how to fix it?
Many thanks.





RE: Strand7 Beam-columns with applied moment and axial load
RE: Strand7 Beam-columns with applied moment and axial load
If you would like to upload the model I will have a look at it.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Strand7 Beam-columns with applied moment and axial load
I have modeled the beam using plate elements.
RE: Strand7 Beam-columns with applied moment and axial load
Restraining every node will also stop the end faces from rotating, so any applied moments will be fully restrained. I suggest you adjust the restraints as follows.
Restrain the bottom flange at both ends in the Y direction.
Restrain the bottom node under the web at one end in all three directions.
Restrain the bottom node under the web at the other end in the X and Y directions (leaving Z free).
That will provide simply supported conditions.
The middle web plates at each end, where you have subdivided them, are not properly connected to the rest of the model. You should replace them with a single plate at each end, connected to other plates at each node.
Finally the transverse axis is X, so you should apply the moment as MX, not MZ, but I would suggest applying the loads as plate edge pressures, to the top and bottom flange anyway.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Strand7 Beam-columns with applied moment and axial load
How does the model look now?
RE: Strand7 Beam-columns with applied moment and axial load
For the moments, create a second load case, and apply just the moments, then have a look at the resulting stresses and deflections.
It would be a good idea to do some background reading to work out what is going on.
I'm not trying to be unhelpful here, but you will learn more if you play with the alternative ways of applying the load yourself.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Strand7 Beam-columns with applied moment and axial load
RE: Strand7 Beam-columns with applied moment and axial load
RE: Strand7 Beam-columns with applied moment and axial load
That's why I suggested you separate out the moment loads in a second load case :)
Unlike beam elements, the in-plane strains of plate elements are defined by the translational deflections of the nodes. They do not have an in-plane curvature, so you cannot apply in-plane moments as node loads or point loads. You can apply a moment as equal and opposite nodal loads, but this will cause large local strains if you apply them to the web. You could apply equal and opposite loads to the flanges, or create rigid links to connect the node at the centre of the web to the nodes at the centres of the flanges, and apply the moment to the central node. The rigid links will then create a couple with loads applied to the top and bottom nodes.
With your units, your moment of 1000 Nmm is equivalent to a 1000N load with an eccentricity of 1 mm, so the effect of the moment will be very small compared with the axial load.
Also note that your resultant axial load (in load case 1) is applied at mid height, but the beam is restrained at the base, so the axial load will generate a moment.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/