Civil Engineering Reference
In-Depth Information
The classical metal plasticity models use Mises or Hill yield surfaces with
associated plastic flow, which allow for isotropic and anisotropic yield,
respectively. The models assume perfect plasticity or isotropic hardening
behavior. Perfect plasticity means that the yield stress does not change with
plastic strain. Isotropic hardening means that the yield surface changes size
uniformly in all directions such that the yield stress increases (or decreases) in
all stress directions as plastic straining occurs. Associated plastic flow means
that as the material yields, the inelastic deformation rate is in the direction of
the normal to the yield surface (the plastic deformation is volume-invariant).
This assumption is generally acceptable for most calculations with metal.
The classical metal plasticity models can be used in any procedure that uses
elements with displacement degrees of freedom. The Mises and Hill yield
surfaces assume that yielding of the metal is independent of the equivalent
pressure stress. The Mises yield surface is used to define isotropic yielding. It
is defined by giving the value of the uniaxial yield stress as a function of uni-
axial equivalent plastic strain as mentioned previously. The Hill yield surface
allows anisotropic yielding to be modeled. Further details regarding the
5.4.3 Material Modeling of Concrete
5.4.3.1 General
There are mainly two material modeling approaches for concrete in ABA-
QUS [1.29], which are concrete smeared cracking and concrete damaged
plasticity. Both models can be used to model plain and reinforced concrete.
The reinforcement bars can be used with both models as previously
highlighted in
Section 5.2
. In the coming sections, the two modeling
approaches are briefly highlighted to enable modelers to choose the appro-
priate approach.
5.4.3.2 Concrete Smeared Cracking
Concrete smeared cracking model in ABAQUS [1.29] provides a general
capability for modeling concrete in all types of structures, including beams,
trusses, shells, and solids. The model can be used for plain concrete, even
though it is intended primarily for the analysis of reinforced concrete
structures. Also, the model can be used with rebar to model concrete rein-
forcement. In addition, concrete smeared cracking model is designed for
applications in which the concrete is subjected to essentially monotonic strain-
ing at low confining pressures. The model consists of an isotropically harden-
ing yield surface that is active when the stress is dominantly compressive and
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