mhscott wrote: ↑Sun May 29, 2022 12:50 pm
Did you restrain the vertical DOF at the top of the pier? It could be the neutral axis of the section moving away from the geometric center, leading to apparent axial forces.
Dear Dr. Scott,
Thank you so much for your reply. By the way, I am a fan of you and following your blog at "
https://portwooddigital.com". The posts there are very informative and helped me a lot
. Thank you!
Sorry but I am confused about "restrain the vertical DOF at the top of the pier" ... I did not do that, and the pier top is free. Before running the NTHA, I applied the axial force at the top. Do you mean that I should restrain the vertical DOF after the axial loading? Looking forward to your reply, and thank you!
I think I may need to provide more information about the pier:
20m;
3D model;
bottom fixed and top free;
50 elements (to be consistent with other piers);
nonlinearBeamColumn;
section Fiber $SecTag -GJ $TorStif { ... (where concrete and steel fibers are assigned)};
mass lumped at each node and a big mass at the top node;
geomTransf PDelta;
constraints Transformation;
system UmfPack;
numberer Plain;
set TestType EnergyIncr;
set algorithmType NewtonLineSearch;
integrator Newmark 0.5 0.25;
Bests,
Eason