大跨度CFRP斜拉桥非线性动力学模型和特性的理论与实验研究

CFRP cables can significantly increase the span of bridges due to their high strength and low density, which make CFRP cable-stayed bridges a promising prospect in bridge construction. However, the whole structure of large-span CFRP cable-stayed bridge becomes more lighter and flexible than conventional bridge, which would lead to the serious nonlinear vibration and bring hidden trouble to bridge safety. Research of the mechanism and control method on the large spatial motion of CFRP cable and CFRP cable-stayed bridges is a key scientific issue that must be addressed before promoting their application. Using the linear and nonlinear dynamic theories and methods, this project aims to establish respectively the linear dynamic model and nonlinear mutli-CFRP cable-shallow arch model of CFRP cable-stayed bridges based on their material, mechanical and structural characteristics. The comprehensive study on the linear and nonlinear dynamics of CFRP cable-stayed bridges will be conducted separately by theoretical and experimental methods. Especially, on the condition of resonance and non-resonance, the nonlinear dynamic behaviors such as the instability, bifurcation, and chaos of motion and mixed-modal interacton of/between CFRP cable and shallow arch under the wind load, vehicle load and earthquakes, is the focus of the project. Some new nonlinear dynamic phenomena maybe be found. The scientific assessment of the natural frequency, deformation, internal force, stress and their law of the CFRP cable-stayed bridges will also be carried out and some effective control strategies for their spatial motion will be proposed. Therefore, the project not only has an important scientific significance but also lays the theoretical foundation of design and construction of large-span CFRP cable-stayed bridges.

CFRP索的高强度和低密度特性能显著提高桥梁跨越能力，使CFRP斜拉桥在桥梁建设中具有广阔的应用前景。大跨度CFRP斜拉桥的结构将更轻、柔性更大，可能出现大幅度的非线性振动，危及桥梁安全。研究大跨度CFRP斜拉桥的大幅空间振动机理和控制方法是推动其应用必须研究的一个关键科学问题。项目拟采用线性和非线性振动研究方法，针对大跨度CFRP斜拉桥的材料、受力及构造特点，建立线性振动模型和多CFRP索-浅拱非线性振动模型。通过理论和实验，研究CFRP斜拉桥整体动力学特性，重点研究在风、车辆和地震等荷载作用下CFRP索与桥面产生共振与非共振时的混合模态相互作用、运动失稳性态、分叉和混沌等非线性动力学行为，可能发现一些新的非线性动力学现象，科学评估结构频率、位移、内力和应力等力学指标的变化规律，并提出有效的控制策略。因此，本研究项目具有重要的科学意义，可为大跨度CFRP斜拉桥的设计和施工奠定理论基础。

过去二十年来，随着斜拉桥在跨度和材料的不断创新，在桥梁工程和力学领域，其复杂的动力学问题一直备受关注。本项目针对斜拉桥的复杂动力学问题，经过4年的理论和实验研究主要取得了以下研究成果：建立了大跨度CFRP斜拉索动力学模型和面内面外线性和非线性动力学理论，并发现在一定条件下系统的单模态和多模态运动可能相互转化；为研究索与边界耦合运动问题，建立了索-质量块和索-梁力学模型，通过构造可解条件建立了索-边界系统多尺度耦合的边界调制方法；通过斜拉桥实验模型，测试和验证了理论研究成果，发现了索、索与索、以及斜拉桥整体多种复杂运动现象并揭示了背后的内共振机制；建立了无背索斜拉桥、漂浮式斜拉桥、半漂浮式斜拉桥和固结式斜拉桥的整体动力学模型和理论，以及大跨度斜拉桥竖弯刚度评估的新方法；建立了大跨度斜拉桥多索-浅拱动力学平面和空间动力学模型和理论，揭示了索与索、索与梁的多种内共振机制；建立了大跨度斜拉桥考虑弹性支承的多索-浅拱平面动力学模型和理论，揭示了斜拉桥复杂动力学行为与支承条件的内在力学规律。该项目的研究，不仅为大跨度斜拉桥的设计奠定了理论基础，更为斜拉桥的振动控制提出了基于非线性动力学新思想和方法，具有重要的科学意义。