Studies On Vibration Response Of Rigid Pavement Based On Aircraft-Pavement Coupled System

According to the provisions of the International Civil Aviation Organization, each member should conduct a comprehensive assessment of the airport runway every four years,but Civil Aviation Administration of China regulates that a comprehensive assessment must be conducted every five years. At present, in most cases the carrying capacity of airport runway are tested using the heavy weight deflectometer technology, in this method the heavy hammer’s percussion is used to simulate effect of the single wheel load acting on pavement,however, there is no comparability in the effect between the simulation load and the actual aircraft total load. In addition, the test can only be conducted in conditions that runway is closed, therefore great economic and social influence will be brought in large and busy airports in which aircrafts taking off and landing day and night. So how to reasonably evaluate carrying capacity of the runway without suspending flight is still a big problem for aviation engineering. Supported by National Science Technology Foundation and National Supercomputer Center in Tianjin, the mathematical relationship between the fundamental frequency and structural parameters of the aircraft-pavement is established, and the bearing capacity evaluation measure which is based on pavement PCN calculated by measured fundamental frequency to provide theoretical basis for the rapid evaluation of airport runway capacity is proposed. The main work and achievements are as follows:1.After comparing the different numerical simulation methods of the airport pavement roughness, trigonometric series synthetic method is selected to generate the airport pavement roughness under the conditions of different pavement levels. Meanwhile the model of pavement and aircraft is analyzed, and the vibration differential equations between them is setted up, based on this, the aircraft-pavement coupling vibration differential equation is built by analyzing the coupling effect between the aircraft and the pavement under the aircraft loads.2. On the basis of the elastic layer system theory, three dimensional finite element analysis model of the pavement structure is built. Considering the pavement random roughness and the aircraft-pavement coupling effect, aircraft moving random loads are obtained when the aircraft acts on the runway, which are loaded on the pavement finite element model with the help of ANSYS, and the corresponding simulation results, such as acceleration and stress, are extracted. The laws of the dynamic response parameters changing with depth under the aircraft moving random loads are systematically analyzed.3. During the process of aircraft taxiing, the excitation load under the aircraft-pavementcoupling effect has an impact on the runway, through simulating the impact and with MATLAB as the tool to do the Fourier transform of the acceleration signals coming from simulation calculation, the first order frequency of the remote observation point is obtained,and the laws that how pavement fundamental frequency is influenced by aircraft landing gear configuration, rebound modulus of sub-grade, airplane carrying capacity and other parameters are also discussed systematically. On this basis and Combining with a large number of finite element calculations, the relationship which is between pavement fundamental frequency with modulus, thickness of the pavement and equivalent modulus of elasticity of foundation is regressed by means of orthogonal test designs.4. A field test was done in an airport, the pavement fundamental frequency is obtained by the analysis of the measured acceleration data, and the pavement bearing capacity PCN which is back-calculated based on the above frequency is well correlated with the airport bulletin PCN, so the theoretical results is proved to be applicable and effective.