Introduction to DIANA

DIANA and ATENA General p

purpose
p finite element analysis
y p program
g
Special features for analysis of concrete, soil and soil-
structure interaction
CEE561
UIUC Almost 200 types of element library

General features 2-Danalysis examples

Analysis Type Material Models Beam-column

Beam column joint Deep beam analysis

Linear static analysis Elasticity

Cracking models
Non linear analysis
Plasticity
Potential flow analysis
Soil specials
Coupled
C l d flow-stress
fl Viscoleasticity
analysis Interface non linear models
Dynamic analysis Temperature or concentration
Euler stability analysis dependent material parameters
Viscoplasticity
Etc.
User-supplied
User supplied material models
 Two pile cap experiment Two pile cap analysis

Failure: 800 kN

Strain profile Stress in rebars

 Animation of wall temperature analysis Material models for concrete

T
Tensile
il behavior
b h i C
Compressive
i behavior
b h i
Strain decomposition Total strain Total strain
= elastic strain = elastic strain
+ strain due to cracking + plastic strain

Total strain Total strain is used for calculation of stress

Di
Discrete
t crack
k U iinterface
Use t f element
l t El ti
Elastic

The first two models belong to smeared crack concept.

The first two models can deal with multiple cracks.

Strain decomposition model Total strain model

Strain is decomposed
p into: Developed
p along
g the lines of MCFT
elastic + plastic for compressive response using plasticity theory The original MCFT does not identify the loading and
elastic + cracking for tensile response using fracture mechanics

concept
unloading, so that one total strain always gives one
stress.
Each strain part has its own stiffness.
In this model, loading and unloading is identified
One total strain can have more than one stress states
andd th
thus one total
t t l strain
t i can hhave ttwo stress
t states.
t t
according to the contribution of each component.
 Discrete crack model Tensile behavior based on fracture mech.

Interface elements are

placed along the Strain decomposition Total strain
anticipated crack line

Difficult to implement as a
new mesh is necessary
when crack propagates

Well suited to the analysis

of very lightly reinforced
or plain concrete

Compressive behavior of total strain crack Fixed and rotating crack modeling

One of the left

In DIANA, both of fixed and rotating crack models are
constitutive relationships available.
can be selected.
Fixed crack model
The direction
Th di i off crackk is
i fi
fixed
d at the
h iinitiation
i i i off crack
k
Compression softening, Shear stress develops along the crack surface.
lateral confinement Shear stiffness is calculated by shear retention factor. G cr G
effect are implemented. is reduced with the increasing crack width.
More appealing to physical nature.
 Fixed and rotating crack modeling Other concrete model (Maekawa model)

Rotating crack model In compression

p regime,
g , damage
g and p
plasticityy
The direction of newly developed crack has different direction than behavior are combined.
initial crack.
The direction of current crack coincides with the p
principal
p tensile The model was derived from cyclic loading data.
stress of concrete.
No shear modeling along the crack surface.

Rebar modeling Introduction to ATENA

Truss element Embeded bar modeling Developed

p byy Cervenka consulting
g
Dr. Cervenka was the winner of competition of
Used in discrete rebar Mesh can be generate without panel test prediction.
modeling antecipating
t i ti th the llocation
ti or size
i
of the reinforcements Nonlinear finite element analysis program
Well suited to model
specialized for structural concrete.
lumped rebars
Element nodes of concrete Provide specialized material models for 2D and 3D
should be coincident with analysis respectively.
the end nodes of rebar Useful information can be found in
element. Difficult to
model http://www.cervenka.cz/Web/
Material models in ATENA Sbeta model

For p
plane stress element
Non-linear behavior in compression
Fracture of concrete in tension based on nonlinear
fracture mechanics
Biaxial strength
g failure criterion
Compression softening
Tension stiffening
Rotating and fixed crack model
Very similar to the total strain crack model in
DIANA

Equivalent uniaxial response Biaxial failure criteria

Defined in the principal According to Kupfer

direction (1969)
fcef and ftef are calculated In here, failure line means
from biaxial stress failure the maximum stress
criteria. envelop
Unloading is a linear Used to determine fcef and
function to the origin.
origin ftef of equivalent uniaxial
Reloading follows the response for given load
path of unloading
p g until it ratio
meets the envelope. Note that there is no
Note that no strain biaxial effect in biaxial
d
decompositioniti tension (Tension cut-off)
tension.
 Fracture plastic model Example tension stiffening 2D

Experimental Setup
For 3
3D analysis
y
Combination of fracture for tension and plasticity
for compression
Strain is decomposed into elastic, plastic and
cracking strains
Very similar to the strain decomposition model in Finite Element Mesh
DIANA

Analysis result Example tension stiffening 3D

Fixed Crack Model Experimental Setup

Rotating Crack Model Finite Element Mesh

 Analysis result Example prestressed beam 3D

Experiment Setup

Crack Width Diagram Crack inside of the Beam

Finite Element Model

Analysis result

Stress and Crack Diagram Stress of Tendons