桥上公路车辆非定常风荷载及对行车安全性的影响研究

Strong winds are one of the main factors threatening the safety of road vehicles driven on the coastal long-span bridges. The refinement model of the unsteady wind loads for road vehicles, caused by crossing event, overtaking and passing through the local area of bridge tower, is of great significance to accurately assess the vehicle driving safety. Combining the methods of wind tunnel model test and CFD numerical simulation, the main research contents of the project include: to overcome the limitations the relative yaw angle method for the static model adopted by the existing research, the steady and unsteady transient aerodynamic effects on vehicles, during the process of crossing, overtaking and passing through the local area of bridge tower under crosswind, are investigated, and it reveals the variation of the transverse transient aerodynamic loads on vehicles driven on bridge; considering the influence of vehicle movement on the local flow field characteristics of bridge deck, the mathematic models reflecting the characteristics of the flow field such as the power spectrum and coherence function of the fluctuating wind are established, it obtained the aerodynamic admittance functions for different types of road vehicles, the unsteady aerodynamic load models for road vehicles are proposed taking into account the influence of the transient crosswind; based on the theory of wind-vehicle-bridge coupling vibration system, the Hilbert Huang transform is employed to analyze the variation characteristics of the time-frequency and spectrum of the bridge-vehicle system, the influences of the transverse transient unsteady aerodynamic loads on the running safety of road vehicles are investigated. The contents are intended for practical needs, research results would be referred for practical guidance or reference.

强风是威胁沿海大跨度桥梁桥上车辆行车安全性的主要因素之一，研究会车、超车及通过桥塔局部区域引起的车辆非定常风荷载精细化模型，对于准确评估车辆行车安全性具有重要意义。本项目采用风洞模型试验和CFD数值模拟相结合的方法，主要研究内容包括：克服现有研究采用的静态模型相对风偏角法的局限性，研究横风环境下桥面汽车在会车、超车及通过桥塔局部区域过程中车辆所受的定常和非定常瞬态气动效应，揭示桥上车辆瞬态横风气动荷载变化规律；考虑车辆运动对桥面局部流场特性的影响，建立脉动风功率谱、相干函数等反映流场特征的数学模型，得到不同类型车辆的气动导纳函数，提出考虑瞬态横风影响的公路车辆非定常气动荷载模型；基于风—汽车—桥耦合振动分析理论，采用希尔伯特—黄变换，分析桥梁—车辆系统的时频和能谱变化特性，研究瞬态横风非定常气动效应对车辆行车安全性的影响。本研究内容面向实际工程需求，研究成果对实际工程有指导或借鉴意义。

强风是威胁沿海大跨度桥梁桥上车辆行车安全性的主要因素之一，本项目围绕侧风环境下车辆会车、超车过程中引起的车辆非定常风荷载特性及桥上车辆行车安全性等关键性问题展开。通过模型风洞试验开展了大型集装箱车和厢式货车在桥面超车、会车过程中的气动荷载特性研究，揭示了车辆超车、会车过程中风载突变的特性及变化规律。开展了桥面局部流场的气动特性研究，根据桥面流场的分布特性，采用车辆气动力和气动力矩等效的方法，通过定义等效风速和比例系数，以反映主梁扰流特性对桥上车辆气动效应的影响。基于COOPER理论，推导了移动车辆的各向脉动分量的自相关系数函数和互相关系数函数，得到了考虑车辆运动的各向脉动风速谱，为车辆非定常气动响应分析奠定了基础。车—桥系统随机振动分析中将自适应高斯积分技术与虚拟激励算法相结合，形成一种高效率的随机振动求解方法，探讨了车—桥系统随机特性对车—桥系统随机动力响应的影响。建立了风-车-桥耦合振动分析框架，提出了车辆行车安全性和舒适性评价标准，分析了不同影响因素（风速、车速、路面不平度等）对车辆和桥梁动力响应的影响。本研究可以为公路管理部门对沿海及内陆强风区桥上车辆的行车安全性和舒适性评估提供一定的理论基础和科学依据。