Civil Engineering Reference
In-Depth Information
Stress
Failure point in compression
(peak stress)
Start of inelastic
behavior
Unload/reload response
Idealised elastic unload/reload response
Strain
Cracking failure
Softening
Figure 5.19 Uniaxial behavior of plain concrete as given in ABAQUS [1.29].
an independent “crack detection surface” that determines if a point fails by
cracking. The model uses oriented damaged elasticity concepts (smeared
cracking) to describe the reversible part of the material's response after crack-
ing failure. The model requires that the linear elastic material model be used to
define elastic properties and cannot be used with local orientations; see
Reinforcement in concrete structures is typically provided by means of
rebars, which are 1D strain theory elements (rods) that can be defined singly
or embedded in oriented surfaces. Rebars are typically used with metal plas-
ticity models to describe the behavior of the rebar material and are super-
posed on a mesh of standard element types used to model the concrete.
With concrete smeared cracking modeling approach, the concrete behavior
is considered independently of the rebar. Effects associated with the rebar/
concrete interface, such as bond slip and dowel action, are modeled approx-
imately by introducing some “tension stiffening” into the concrete model-
ing to simulate load transfer across cracks through the rebar. Defining the
rebar can be tedious in complex problems, but it is important that this be
done accurately since it may cause an analysis to fail due to lack of reinforce-
ment in key regions of a model.
Concrete smeared cracking model is intended as a model of concrete
behavior for relatively monotonic loadings under fairly low confining pres-
sures (less than 4-5
the magnitude of the largest stress that can be carried by
the concrete in uniaxial compression); see
Figure 5.20
. Cracking is assumed
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