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Finite Element Simulation of the Response of No-Tension
Materials
Alieh Alipour & Tom ScarpasDelft University of Technology
Section of Pavement Engineering
Alieh Alipour & Tom Scarpas
Simulation No-Tension
characteristics of aggregates
No-Tension Materials
Prediction pavement performance
Decreasing load-induced stress transferred to subgrade
Providing support for the surface layer
Drainage
Protection subgrade against frost
Unbound aggregates (Base & Subbase Layer)
Alieh Alipour & Tom Scarpas
Unbound aggregates modelling (FEM)
Cross-anisotropic
Different Horizontal and vertical moduli
Not suitable for thin AC layer
Unable to predict the nonlinear & stress dependent response of aggregates
Wrong prediction of tensile stresses at bottom of base layer
Linear isotropic elastic model
Nonlinear Stress dependent response
Different Horizontal & vertical moduli
Difficulties in determining anisotropic material properties
Nonlinear cross anisotropic model
No-tension Model
Alieh Alipour & Tom Scarpas
Constitutive Model: Modified Hook’s Law
1D
Alieh Alipour & Tom Scarpas
Principal Strains
Strain
Constitutive Model: Principal Strains
Alieh Alipour & Tom Scarpas
Constitutive Model: Special Operator
Special
Operator
Alieh Alipour & Tom Scarpas
Constitutive Model: Special Operator
Special
Operator
Alieh Alipour & Tom Scarpas
Constitutive Model: Strain energy function
removal of the stiffness & stress along
principal tensile strain direction
Alieh Alipour & Tom Scarpas
Principal Stresses
Stresses
Constitutive Model: Principal Stresses
Alieh Alipour & Tom Scarpas
Tangent Moduli
Constitutive Model: Implementing in FEM
Stresses
FEM
Alieh Alipour & Tom Scarpas
(a) (b)
Validation of the Model
No-Tension
Hyperelastic
Hor
izon
tal s
trai
n
Time (sec)
Alieh Alipour & Tom Scarpas
Tire
Horizontal strain
Compressive strain
AC layer
Base layer
Material Type Model E (MPa) Poisson’s ratio
AC layer Hyperelastic Material
3500 0.35
Base Hyperelastic Material
600 0.35
Base No-tension Material
600 0.35
Results of Flexible Pavement Simulation
Alieh Alipour & Tom Scarpas
Results of Flexible Pavement Simulation
Hyperelastic material No-Tension material
Alieh Alipour & Tom Scarpas
Results: Deflection of AC layer
No-Tension
Hyperelastic
Def
lect
ion
(mm
)
Distance from CL ( mm)
Alieh Alipour & Tom Scarpas
Results: Horizontal Strain (bottom of AC layer)
No-Tension Hyperelastic
Hor
izon
tal s
trai
n
Distance from CL ( mm)
Alieh Alipour & Tom Scarpas
Results: Vertical strain (top of base layer)
No-Tension
Hyperelastic
Vert
ical
str
ain
Distance from CL ( mm)
Alieh Alipour & Tom Scarpas
Results: Effect of Poisson’s ratioD
efle
ctio
n (m
m)
Distance from CL ( mm)
Poisson’s ratio=0.1Poisson’s ratio=0.35Poisson’s ratio=0.45
Alieh Alipour & Tom Scarpas
Results: State of stress (Base Layer) St
ress
in Y
dire
ctio
n
Distance from CL ( mm)
No-tension Y=1450 mmHyperelastic Y=1450 mmNo-tension Y=1350 mmHyperelastic Y=1350 mm
Alieh Alipour & Tom Scarpas
Conclusion
No-Tension Material Model is implemented in FEM.
Effect of using no-tension model for base layer on pavement performance is significant.
The deformation at top and horizontal strain at bottom of AC layer are higher when no-tension model is used.
No-Tension Material Model is sensitive to Poisson’s ratio.
Alieh Alipour & Tom ScarpasDelft University of Technology
Section of Pavement Engineering
Thank You for Your Attention!
