The Research On The Theory Of Pavement Relatively Roughness Related To Aircraft Type

Pavement is the most important airport infrastructure, and its quality directly affects airports' service level. In order to ensure the safety during operation, airport pavement evaluation must be done regularly to judge if the relative function can meet using requirements continuely. During airport pavement evaluation, the detection and assessment of pavement roughness is a content must be carried out, because the pavement roughness is one of the most important index characterizing pavement quality. Pavement of bad roughness state causes violent vibration of the fuselage, thus affecting the ride comfort and may lead the goods in bad condition, increase mechanical wear of airplane, make aircraft structure fatigue and increase fuel consumption, in addition, the additional vibration will increase the role of the impact and thus reduce the service life of pavement, and the currently used method for pavement evaluation is suitable for the detection and evaluation of highway but not for airport pavement because of its fault in principle, performancing as:quarter car model based on can only represent one measuring line's roughness condition,while civil aircraft has a large geometry scale and its bumping effect depends on pavement roughness condition under all the landing gear wheels and has a poor relevance with single measuring line, so it is unable to measure the coupling effect produced by pavement under all wheels. It provides a new way to solve the above problem by modelling full size aircraft according to the characteristics of its landing gear and solving the vibration equations and evaluating pavement roughness on the basis of the coupling effect produced by pavement under all wheels. But at present, the research of this technology is still in the conceptual stage both here and abroad.Aiming at building the pavement roughness evaluation system through the study of the vibration equation of full-scale aircraft model, the main works are as follows:First, basing on the currently high frequency using models- the Boeing 737-800 aircraft landing gear characteristics and size characteristics, a full scale aircraft vibration model was built, with this as basis, the three degree of freedom vibration differential equation of the aircraft model when taxiing on pavement was derived, then,the standard parameters of the vibration equation was explored and selected.Second, through the study of the characteristics of the airport pavement roughness and the exploring of the distribution rule of pavement random elevation, different level airport pavements was constructed using the harmonic superposition method in MATLAB environment. Taking SIMULINK as the platform, the pavement roughness evaluation system's first subsystem-pavement excitation input subsystem was constructed. To solve the three degree of freedom vibration differential equation of the aircraft, aircraft vibration processing subsystem was developed in the SIMULINK platform and got the aircraft's vibration responses: the vertical displacement of the centroid position, the amount of longitudinal pitch and the amount of horizontal roll.Third, with three vibration response quantities of the aircraft when taxiing on rough pavements as basis, to reflect the pavement roughness degree objectively and considering the dimensional coordination, the concept-Full Size Aircraft Roughness Index FARI was proposed, namely, let the longitudinal pitch angle ? multiply the distance of the airplane model centroid and the front landing gear a, and let the airplane roll angle ? multiply half of the main landing gear spacing l, and make the superposition of absolute value of three vertical displacement of fuselage within unit taxiing distance be the airport pavement roughness evaluation index. And then, the index calculation system of FARI was constructed using SIMULINK function modules.Fourth, by integrating the vibration processing subsystem, the pavement excitation input subsystem and the FARI index calculation subsystem the pavement roughness evaluation system was got. Using this system, with the road surface midline, left and right main wheel tracks section elevation as basic inputs, distribution of the airport pavement roughness index FARI can be obtained. Through the correlation analysis of FARI and IRI with the aircraft vibration response-weighted RMS acceleration aw respectively, it is found that the correlation coefficient of FARI and aw is 0.9806, meanwhile, the correlation coefficient of IRI and aw is 0.8276, and this indicating that it will be more objective and scientific to evaluate pavement roughness by FARI. According to the research above, and in the light of the relationship between weighted RMS acceleration aw and the driving comfort,the pavement grade division standard based on FARI was put forward, and theevaluation process was given out.It not only completed the theoretical research related to the proposed concept but also developed a software system needs to realize the idea, and if we can find a suitable channel which can bring about the method into practical,the status that there are problems in airport pavement roughness evaluation theory will have a big change.