Whenever I use shell apply command or equivalent FISH function for applying pressure, it works. But whenever I use struct node fix velocity-z command and struct node initialize velocity-z command to apply equivalent velocity controlled loading in shell, it does not work. I am getting output as shown here. Also, the direction vector arrows are also not making sense physically nor are the displacement patterns.
Here is the code I used. I tried running similar code for geogrids and piles but they all seemed to work. What kind of error is this?
Also, the direction of displacement vectors in shell does not change on changing the sign of the applied velocity vectors and the magnitude of displacement vectors is very very small and does not increase even upon applying a large displacement magnitude. I am not able to understand where I made the mistake.
I am not sure why the shell elements won’t move under the velocity conditions you supplied. However, if you switch to a liner structural element and provide coupling properties it does work. I hope that helps.
Thankyou so much for the help ! It worked with liner element, but I am still not sure why it won’t work with the shell element. Is there some reason for shell element to not work as such?
It looks like the problem comes from how velocity-controlled loading interacts with shell elements in FLAC3D. Unlike geogrids or piles, shell elements don’t always respond well to direct velocity inputs like struct node fix velocity-z or initialize velocity-z, which is why you’re seeing almost no displacement and odd vector behavior. The shell apply command works better because it applies pressure in a way that shell elements can actually respond to. If you really need to use velocity, consider applying it to connected structural elements or check that the mesh and boundary conditions allow the shell to move properly. It’s not necessarily a code error—just how shell mechanics work differently in FLAC3D.
