随机激励飞机荷载作用下道基空间变形行为

Due to the characters of complex landing gears and high taxi speed of the new generation large aircrafts (NGLA), and the excitation by pavement roughness, the aircraft loads enhance superimposition of additional stresses in subgrade, increase stress level and influence depth, hence result in more settlement and decrease of pavement roughness performance, threatening pavement structure and flight safety. The design methods, which ignore aircraft load or utilize static load, cannot take the forementioned influences of NGLA into account. In the project, firstly, the 3D time domain character of in-field pavement roughness will be obtained to simulate stochastic excitation, and full size aircraft models by virtual prototype technology will be established to investigate aircraft dynamic load spectrum under different conditions, such as rising, landing, taxiing and braking. Secondly, the spatial distribution characteristics of additional stress in subgrade will be investigated by three-dimension finite element simulation and structure influence surfaces method, and then spatial deviation of aircraft and superimposition of multi-wheels load will be highlighted. Lastly, available accumulated plastic strain model of compacted and soft soil will be compared and chosen, and in the view of dynamic load enhancement effect induced by subgrade deformation, cyclic iterative calculation method and three-dimension graphic presentation technique will be utilized to address the spatial and temporal characteristics of subgrade deformation. The results will be useful not only for subgrade design, but also for pavement roughness analysis and evaluation.

受道面不平整的激励，新一代大型飞机的复杂起落架构型和高速滑跑特征，将增强道基附加应力的叠加效应，提升应力水平和影响深度，致使道基变形对总体沉降和平整度劣化的影响更为突出，进而对道面结构和飞行安全造成巨大威胁。忽略飞机荷载或仅以静载考虑的设计方法，则难以适应飞机大型化和航班密集化的新挑战。项目利用现场实测数据构建道面不平整三维时域激励，采取虚拟样机技术，研究起降、滑跑和制动等飞机多态地面动力行为下的荷载谱；面向飞机地面动力行为的位置偏移和多轮荷载的空间叠加，运用三维有限元仿真和结构影响面法，研究随机激励动载下道基附加应力的空间分布特征；甄选适用于压实土与软弱土的塑性累积应变模型，并进一步考虑道基变形导致的动载增强效应，运用循环迭代算法和三维图形表达技术，揭示和演绎道基空间变形的动态演化行为。预期成果不仅可为场道地基设计提供借鉴，亦可为道面平整度分析与评价提供支撑。

受道面不平整的激励，新一代大型飞机的复杂起落架构型和高速滑跑特征，将增强道基附加应力的叠加效应，提升应力水平和影响深度，致使道基变形对总体沉降和平整度劣化的影响更为突出，进而对道面结构和飞行安全造成巨大威胁。本项目克服传统车载式激光平整度仪难以捕获长波的缺陷，提出了“长波+短波”的跑道全波段不平整检测新方法，并在全国20条跑道进行现场应用，揭示了道面不平整频谱参数统计特征，发现道面不平整系数C主要集中在0~0.4之间，频率指数w主要分布在2.0~2.6之间，从而基于统计特征构建了典型道面不平整激励时域模型。结合虚拟样机技术，建立了民用机型的整机仿真模型库，获得了不平整激励下飞机随机动力荷载谱并提出了飞机动荷载预估方程，在道面不平整频谱参数的主要分布范围内最大动载系数可达1.20。采用三维道面-道基有限元模型，构建了复杂荷载条件下道基应力响应影响面，揭示了道面不平整、升力作用和速度放大效应综合影响下的道基应力分布特征，表明随着道面平整度的劣化，飞机荷载对道基应力的主导因素逐渐由升力转化为道面激励与速度效应的增强作用。综合考虑飞机轮迹分布、道面不平整、速度分布、交通参数等因素，提出了分块分层的道基空间变形计算方法，并揭示了道面平整度、道基结构和机型对道基空间变形特征的影响；进一步，基于道基空间变形与道面平整度的相互作用，开发了道基空间变形的循环迭代算法，揭示了道基空间变形动态演变规律。研究成果不仅可支撑道基长期沉降预估和道面平整度检测与评价，还可为场道地基处理与设计提供借鉴，延长跑道服役寿命。依托项目研究，共计发表学术论文8篇，参与国际学术交流2次，申请发明专利2项，培养博士后1名，博士研究生2名，硕士研究生3名。