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Re: Pushover

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Rudra -

You can get reasonable results using bilinear materials. Done properly it's
probably a better simulation of reality, since members don't suddenly pop free
diring a collapse until the deformations become enomous.

In fact, bi-linear model will pop members free suddenly when tangent modulus
changes at the kink from a finite value to zero.

Bi-linear is not necessarily elastic-perfectly plastic.  It just
requires that there be two slopes, not that the second one be zero.

It's done with ANSYS, LS-DYNA and ABAQUS (to name only 3) every day.
It's not for the newbie and requires a solid understanding of the physics
involved, but that's the way non-linearities are done these days.

'Continue increasing the load' and 'single nolinear model of every thing'
refers to algorithm of pushover analysis and not what a user does. Software
takes care of 'increasing the load' and making 'multiple non-linear models'.

What multiple nonlinear models?  For most decent FEM software,
one creates a *single* model for the material and the software
simply iterates on a convergence metric (for example unbalanced
load) until the residuals are within tolerance.  I can see how
one might think of the stifness matrix updating as "creation of
multiple models", but that is not typically what one means when
describing creation of multiple nonlinear models.  In fact, one
might better refer to that process as the creation of multiple
locally-linear models.

Just my $0.02,

Charley

--
Charles Hamilton, PhD EIT               Faculty Fellow
Department of Civil and                 Phone: 949.824.3752
    Environmental Engineering           FAX:   949.824.2117
University of California, Irvine        Email: chamilto(--nospam--at)uci.edu




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