1. Finite element analysis of effects of asphalt pavement distresses on FWD dynamic deflection basin
Qinglong You
Jinglian Ma
Xin Qiu
Chang’an University

2. Outline Introduction Objective Development of 3-D FE Model
Parameters of pavement structure and material
Three dimensional finite element model
Analysis and Results
Effect of layer interface between AC and BC layers on deflection
Effect of cracking on deflection
Conclusions

3. Introduction
Many asphalt pavements appeared a certain degree of distresses in China
FWD is currently used by most highway agencies to determine the structural condition of the highway network

4. Introduction
The pavement distress such as cracks, the layer interface between an AC layer and a base layer can influence the FWD to evaluate the strength

5. Objective
Development of 3-D FE Model to simulate the distress on the effect of dynamic deflection basin
The effect of interlayer contact between surface course and base course were analyzed
The effect of a single transverse cracks, multiple-transverse cracks, longitudinal cracks and block crack on FWD dynamic deflection basin were analyzed.

6. Development of 3-D FE Model
Material properties of pavement sections
Layer
Thick-
ness
(cm)
Modulus
(MPa)
Poisson ratio
Density
(kg·m-3)
Damping
ratio AC 16
3 000
0.35
2 200
0.05 BC 40
5 000
0.25
2 100
Sub-BC 15
250
1 900 SG －
150
0.40
1 800
The FWD load model
number d1 d2 d3 d4 d5 d6 d7 d8 d9
distance 20 30 60 90
120
150
180
210

7. Development of 3-D FE Model
Build a 3-D FE pavement model
30m in x-direction, 30m in the y-direction, and 10m in the z-direction.
Fixed constraint was assigned to the model bottom, while normal displacement constraint was applied to the side areas of the model
3-D FE Model with Transversal Cracks
3-D FE Model with a block cracks

8. Analysis and Results
Effect of layer interface between AC and BC layers on deflection

9. Analysis and Results
Effect of transverse crack on dynamic deflection basin
Effect of transverse single crack on deflections
d=16cm
d=45cm

10. Analysis and Results
Effect of transverse crack on dynamic deflection basin
Effect of transverse single crack on deflections
d=110cm
d=165cm

11. Analysis and Results
Effect of transverse crack on dynamic deflection basin
Effect of transverse multiple cracks on deflections

12. Analysis and Results
Effect of longitudinal cracks on dynamic deflection basin
Effect of transverse multiple cracks on deflections
Loading Position and Dynamic Deflection Basin
Crack Gap and Dynamic Deflection Basin

13. Analysis and Results
Effect of longitudinal cracks on dynamic deflection basin
Block cracks
The results indicate that the distribution characteristic has an increasing discrepancy between intact pavements and distressed pavements with increase in crack interval.

14. Conclusions
The layer interface has a strong influence on deflection points close to the load center
When the friction coefficient between the layers is greater than 15, the difference of the last 5 points is no more than 2%.
For the transverse multiple crack, the wider the crack width is, the smaller the influence on deflection.
When loading point distance from longitudinal cracks is greater than 35 cm, the dynamic deflection is not obvious.

15. Conclusions (2)
With the increase in block spacing, there is an increasing difference of the deflection for the first four measurement points.
For the transverse single crack, when the distance between the FWD load point and crack is greater than 110cm, the deflection is the same between the cracked pavement and non-cracked pavement.
Influence of crack width on the deflection is increasing with the increase of the distance from the load center.
The impact of different crack width is not obvious.

16. Thank You
Questions ?