【作者】 张鹤；

【导师】 谢旭；

【作者基本信息】 浙江大学 ， 桥梁与隧道工程， 2010， 博士

【摘要】 随着交通运输的发展,交通荷载引起的桥梁结构振动问题日益突出,尤其是复杂异形桥梁的车桥耦合振动、交通荷载作用下斜拉桥及斜拉索的振动问题以及由车桥振动衍生的低频噪声问题等,这些问题为桥梁工程的相关理论研究提出了新的挑战。传统方法和理论模型已无法满足复杂结构、新结构、新问题提出的新要求,因此有必要发展新的理论模型和计算方法。本文针对复杂异形钢管混凝土拱桥,建立考虑吊杆局部振动影响的空间索-拱-梁组合有限元模型。针对吊杆采用空间铰接杆模型,并引入自由度凝聚概念,以吊杆基本振型代替索单元体系的所有自由度,从而克服传统以索单元直接计算吊杆振动所造成的计算效率低的缺点。以宁波长丰大桥的设计方案为对象,应用新型桥梁模型结合多质点体系车辆模型的车桥耦合振动理论,研究路面粗糙度、行车速度、结构阻尼对车辆轮压荷载、拱肋和主梁的挠度及拉索张力冲击系数的影响。针对中等跨径斜拉桥的交通振动问题,建立考虑拉索侧向振动的有限元方法,以杭州湾跨海大桥北航道桥为例,分析该类斜拉桥的交通振动特性和动力冲击效应。针对超大跨径斜拉桥的拉索振动问题,建立基于车桥耦合振动理论的柔性拉索在支点激励下非线性振动理论,以跨径1400 m的斜拉桥设计方案为对象,分析不同行车条件下钢和CFRP拉索的非线性振动响应,探讨CFRP拉索在斜拉桥中的应用前景。针对车桥耦合振动辐射低频噪声问题,本文开展了细致深入的研究。首先采用基于点声源的解析解法对简支钢板梁桥振动辐射低频噪声进行数值模拟,这里建立考虑剪切板影响的格子梁模型并采用有限单元法(FEM)计算得到车桥耦合振动响应。其次,针对桥梁辐射声场推导三维边界积分方程,并采用边界元法(BEM)进行求解并自行开发BEM程序代码,从而与钢板梁桥结构动力分析的FEM构成车桥耦合振动辐射低频噪声的FEM-BEM混合求解体系。最后,采用镜像法考察地面边界对声波的反射作用,综合评估车桥耦合振动辐射低频噪声在桥梁附近空间的分布特性和声压水平。将所提FEM-BEM混合求解体系用于简支和连续钢板梁桥车桥耦合振动辐射低频噪声的稳态和瞬态响应分析。通过与桥梁振动辐射噪声现场实测数据的对比,验证三维边界积分公式和BEM程序的正确性以及FEM-BEM混合求解方法的计算精度。给出了振动桥梁附近噪声水平的数值结果、声压的空间分布及其随时间的变化规律。详细讨论了路面粗糙度、车速度以及桥面距地高度的变化对声压水平和声场分布特性的影响。利用所提FEM-BEM混合方法开展桥梁减振降噪研究。以连续钢板梁桥为例,提出桥梁减振降噪设计方案,并采用该方法评估各方案的可行性和降噪效果,最终提出有效的减振降噪措施。更多还原

【Abstract】 With the rapid development in transportation of China, bridges have encountered increasing new dynamic problems due to heavy traffic load, including vehicle-bridge coupling vibration (VBCV) of bridges with complex configurations, vibration of cable-stayed bridges and stay cables due traffic load, and low-frequency noise induced by vehicle-bridge vibrations, etc. The traditional methodologies are not always applicable for these new problems, for which great endeavor should be made to establish new models and methodologies.In this thesis, a finite element (FE) model of spatial cable-arch-beam system including the effects of local vibration of cables is developed for concrete-filled steel tube arch bridges having complex profiles. For each hanger cable, the multiple degrees of freedom (MDOF) are reduced to two end nodes by replacing all of inner nodes using the eigen-functions of the whole cable, thus avoiding heavy computational costs in the traditional FE simulations with direct use of cable elements. Based on the theory of VBCV with a vehicle model of MDOF, the newly proposed model is then applied to simulate the Changfeng Bridge in Ningbo. Intensive investigations are performed to the effects of road surface roughness, vehicle velocity, and structural damping on wheel load and impact factors of arch ribs, main girder, and cable tension.The VBCV of cable-stayed bridges (CSB) are also studied using the proposed FE model considering the effects of local vibration of stay cables. As a case of medium-span CSB, the subpart of Hangzhou Bay Bridge over the north channel is analyzed with emphasis on the impact effects on its dynamic responses. For super long-span CSB, attentions are focused on the vibration of stay cables. The equations of motion in incremental forms are established for the nonlinear vibration of long and flexible stay cables based on the theory of VBCV. A long span CSB with span of 1400 m is investigated as an example. Both nonlinear vibrations of steel and CFRP cables are analyzed comparatively, and the potential applicability of CFRP cables in long-span CSB is evaluated.A major part of the thesis is devoted to the low-frequency noise induced by the vibration of bridges. Firstly, numerical results based on the analytical solutions for acoustic radiation of point source are presented for a simply supported steel girder bridge. Here, the bridge deck is modeled as a beam-plate system considering merely the shear deformation of the plates fully supported by beams. Secondly, the boundary integral equations are derived for three-dimensional sound field, which is solved using the boundary element method (BEM). Thus, a combined method of FEM-BEM is developed for the problem of VBCV-induced low-frequency noise for steel girder bridges. Finally, the image method is adopted to incorporate the effects of reflection of acoustic waves by the ground on the sound field near the bridge deck.The proposed hybrid FEM-BEM is employed to analyze to the steady-state and transient acoustic radiation by the VBCV of simply supported or continuous steel girder bridges. By comparing numerical results to the on-site tested data, the correctness of the present formulations and BEM code, as well as the effectiveness and efficiency of the proposed method, is firmly validated. Numerical results are given both for the noise level around the bridge deck and for the distribution of sound pressure in spatial and time domains. Comprehensive analyses are carried out against the effects of road surface roughness, velocity of vehicles, and distance of bridge deck away from the ground on the noise level and distributions of sound field. Finally, the hybrid FEM-BEM is applied to evaluate and verify effective strategies for noise reduction for continuous steel girder bridges.更多还原