Asphalt Overlay Design Theory and Method for Airport Runway Pavements under Complicated Conditions
|Course||Road and Railway Engineering|
|Keywords||airport runway asphalt overlay complicated conditions structural design method three-dimensional finite element method mechanical response multi-layered pavement structure cumulative damage pass-to-coverage ratio complex gear configuration|
With rapidly increasing of air traffic and the emerging of new generation large aircraft, some early built airport runway pavements mangle, which results in the decreasing of pavements performance. Reinforcement and covering are urgently needed to improve performance and prolong life span of pavements. Asphalt overlay is an effective way to improve pavement structural and function performance of runway. This technical means has been already widely implemented in many airports runway pavements overlay projects in the world, and a lot of successful experience is accumulated. However, overlaying faces so many problems on theory, method et al, because of increasingly complicated conditions of traffic, climate, pavement structure and operation, which restricts the development of internal airport engineering.At present, overlay design method of airport runway pavements has already turned to mechanics-experience method based on elastic-layer theory or finite element method from experience method which is familiar with us. Rational design method does not form yet, while internal overlay design method still uses overseas design method or highway engineering experience for reference chronically. In order to guide the similar airport engineering, establishing runway pavements overlay design theory and method is urgently and necessarily under increasingly complicated conditions of traffic, climate, pavement structure and operation.Relying on overlay project of Hongqiao international airport in 2005, analyzing various complicated conditions this project faced, asphalt overlay design theory and method for airport runway pavements is established under complicated conditions by experiments, in-situ testing, data counts, theoretical analysis, numerical simulation, experience summary et al. Firstly, the index of pavements evaluation and standard of decision making factors are put forward, which is related to structure performance, function performance and distress conditions. Based on the analysis of decision making factors, determination criterion of overlay is proposed which divided structure or functionality separately. In the foundation of the classification of existing pavement using, the influence on asphalt overlay which distress on existing pavement brought from is analyzed, and then the corresponding partial repair measure is proposed. Then, a three-dimensional numerical analysis model is established by use of ABAQUS, which consists of nine blocks full-scale slabs, considering joint loading-transfer and contact effect sufficiently. This model can be used to analyze mechanical responses bring from aircraft ties. Computing results indicate there is no notable difference of maximum tensile stress on the bottom of upper overlay, even the gears load on different locations of pavements, therefore, critical loading position may not be considered in design procedures. On the other hand, over-loading effect the complicated landing gear configuration adding to the overlay is obvious. So, interaction between landing gears should be considered sufficiently when design. Asphalt overlay design theory and method is established, by which cumulative damage theory of Miner Law and pass-to-coverage ratio theory are adopted, fatigue cracking strain flexural-tensile stress, the shear stress of asphalt pavement on joint, fatigue equation brought forward by FAA. Lastly, this new method is made use of calculation of existing pavements of Hongqiao international airport, which indicates that the pavement can be survived to 2013 while enforcement is not needed.Asphalt overlay design theory and method under complicated conditions is established via the study on airport runway pavement overlay design to solve the common problem when implementing overlay. The gains will provide the scientific basis for relevance projects.