Journal of Engineering Mechanics ASCE, 124 (1998), 277-284.
ROTATING CRACK MODEL
WITH TRANSITION TO SCALAR DAMAGE
Milan Jirásek and
Thomas Zimmermann
Swiss Federal Institute of Technology
LSC
-DGC,
EPFL,
1015 Lausanne,
Switzerland
Abstract
Traditional smeared-crack models for concrete fracture are known to
suffer by stress locking
(meaning here spurious stress
transfer across widely opening cracks), mesh-induced directional bias,
and possible instability at late stages of the loading process.
The present paper develops
a new model based on a combination of the standard rotating crack model
with the scalar damage concept. The combined model keeps the anisotropic
character of the rotating crack but it does not transfer spurious
stresses across widely open cracks. This is documented by several
examples.
The model is then
extended to a nonlocal formulation, which not only acts as an efficient
localization limiter but also alleviates mesh-induced directional bias.
Transition to damage can prevent
a special type of material instability arising due to negative shear
stiffness terms in the rotating crack model.
Summary and Conclusions
A model combining the advantages of the standard rotating crack model and the
isotropic damage model has been developed. The new rotating crack model with
transition to scalar damage (RC-SD) keeps the anisotropic character of the RCM
but it does not transfer spurious stresses across widely
open cracks. The model has been tested on several examples,
and it seems to provide reasonable results if the
transition from rotating crack to damage takes place at the point
where the bilinear stress-separation curve changes its slope.
The RC-SD model has been extended to a nonlocal formulation.
Transition to damage
not only removes spurious stress transfer across widely opening
cracks but also prevents the model from losing material stability
due to negative shear stiffness terms that may arise in the standard
RCM formulation. The nonlocal formulation substantially alleviates
mesh-induced directional bias.
Please send me an email
if you wish to receive the complete paper.
EPFL /
13 December 1996 /
Milan.Jirasek@epfl.ch