Shell undergoing finite rotations

Geometrically nonlinear analysis of a cantilever rolling up under the action of a point moment, performed with shell finite elements.

Here we investigate the roll-up problem previously considered for frames, now with corotational shells.

As always, we begin by creating a Model (see for example this problem).

import opensees.openseespy as ops

model = ops.Model(ndm=3, ndf=6)

model -ndm 3 -ndf 6

Next we create an ElasticShell  section.

E = 1e4
thickness = 1.0
nu = 0.0
model.section("ElasticShell", 1, E, nu, thickness)

#                          E      nu  thick
section ElasticShell  1   1.0e4  0.0   1.0

The loading will be applied in 40 increments.

In the Python version, we’ll create a veux.Artist  before starting the analysis in order to draw snapshots of the deformed shape throughout the deformation.

# Render the reference configuration
artist = veux.create_artist(model, vertical=3)
artist.draw_surfaces()
artist.draw_outlines()

Now we proceed to analyze  :

u = []
load = []
for i in range(nsteps):
    if ops.analyze(1) != 0:
        break
    ctime += dt
    if ctime > dt_record:
        ctime = 0.0
        artist.draw_outlines(state=ops.nodeDisp)

    load[i+1] = ops.getTime()
    u[i+1]   =  ops.nodeDisp(tip, 3)

After running the Python variant of the analysis, the following plot is generated: