# Dynamic Response Analysis of Airport Pavement under Impact Loading
## 5 Result and Analysis  
The impact of the aircraft on the pavement structure has the characteristics of short-time strong loading [25]. The whole landing process is a complex damage process with a short time and a high strain rate, which also involves the transfer and exchange of contact surface impact energy. The damage mechanism is very complicated [26]. In this paper, the same locations of different structures of an airport runway were selected as the research object, with point A on the top of the surface, point B at the bottom of the surface, point C at the bottom of the base, point D on the top of the soil foundation, and point E at the  
Figure 8: Airport pavement dynamic response cloud charts at various sinking speeds. (**a**) Conditions: tire pressure 2.0 mpa, landing pitch angle 3\({}^{\circ}\), sinking speed 1 m/s. (**b**) Conditions: tire pressure 2.0 mpa, landing pitch angle 3\({}^{\circ}\), sinking speed 2 m/s. (**c**) Conditions: tire pressure 2.0 mpa, landing pitch angle 3\({}^{\circ}\), sinking speed 3 m/s. Figure 7: Aircraft track during landing. bottom of the soil foundation. The maximum value and corresponding time of the response parameters such as equivalent stress, effective strain, and the vertical displacement of each layer under different tire pressures, landing pitch angles, and sinking speeds were analyzed, and the impact resistance mechanism of the airport runway was revealed. The maximum effective stress, effective strain, and vertical displacement at each point with different influencing factors, as well as the corresponding time at which the maximum value was reached, are shown in Figures 9-11. From Figure 9, it can be seen that the maximum equivalent stress, effective strain, and displacement in the vertical direction at each layer increased with the increase in the tire pressure at a given landing pitch angle and sinking speed. Figure 9a illustrates the effect of tire pressure on the maximum equivalent stress at each point, in which the maximum stress at 2.0 MPa tire pressure increased by 14.2% and 29.8% compared with 1.5 MPa and 1.0 MPa, respectively. The stress values of the remaining structures also increased with the increase in the tire pressure, but the growth rate was smaller, indicating that the effect of tire pressure on the flexural tensile stress at the bottom of the layers of the airport pavement was more significant. Figure 9b presents the effect of tire pressure on the maximum effective strain of each layer during the impact process of aircraft landing. The maximum value of the effective strain at the top of the soil foundation under 2.0 MPa tire pressure was 7.8% and 19.1% higher than that of 1.5 MPa and 1.0 MPa, respectively. The maximum effective strain value at the top of the soil foundation was the largest under the same tire pressure, which was 1.09 times, 1.22 times, and 1.20 times the strain of the bottom of the soil foundation, indicating that the soil foundation can withstand the largest deformation, followed by the surface and the base. The difference in the strain values of the different layers is closely related to the modulus and thickness of the material. The differences in the strain values have a close relationship with the elastic modulus and thickness, and the effect of the former being more significant. Figure 9c shows the changes in the vertical displacement of each structure during the contact between the tire and the pavement. From the figure, it can be seen that the vertical displacement gradually decreases as the depth increases, and the upper and lower displacements of the surface are similar. Under different tire pressures, the maximum vertical displacement at the top of the surface at a tire pressure of 2.0 MPa is 10.7% and 22.2% higher than that at 1.5 MPa and 1.0 MPa, respectively.