Fatigue of Airport Pavements

As part of FAA's program for developing a unified methodology for design and analysis of airport pavements, SRI International developed a 3-dimensional, nonlinear, dynamic, finite element capability for analyzing stresses and damage in pavements due to traffic loads. A physically-based constitutive model for pavement including fatigue cracking response was developed and implemented into the public domain version of the three-dimensional, nonlinear, finite element code, DYNA3D.

As a demonstration of our approach, we analyzed the rolling of a pair of wheels configured as the landing gear of a 727 over a Portland cement (PC) concrete pavement, as shown in Figure 1 . In the analysis, the wheels start on the right side of the pavement slab and are moving to the left at a speed of 100 mph (45 m/s).

The peak stresses calculated in the pavement were well below the strength of the pavement, but large enough to cause a small amount of fatigue cracking. Figure 2 shows the accumulation of cracking damage for a single landing gear load cycle. Each loading produced by the passage of the landing gear causes a very small increment in damage. However, using our lifetime prediction technique to account for the nonlinear accumulation of fatigue damage, we can estimate the number of cycles to cause complete fracture of this pavement.

The main objective of the FAA program was to show feasibility of developing a three-dimensional finite element analysis capability for pavements. Our results showed that such a capability is not only feasible, but well on the way to becoming a useful tool for pavement analysis and design.

Figure 1 Runway Fatigue Model Landing gear and runway mesh for the concrete fatigue damage Simulations
Figure 2 Calculated Fatigue Damage Dynamic simulation of a single landing gear load cycle along the runway.

Reference

• L. Seaman, J. W. Simons, D. A. Shockey, R. F. Carmichael, and B. Frank McCullough,"Unified Airport Pavement Design Procedure", Final Report to FAA, contract no. DTRS-57-89-C-00008, July 1991

Contact Us
Don Shockey
Director, Center for Fracture Physics
Phone: 650-859-2587
Email: donald.shockey@sri.com