基于响应传递比的桥梁结构应变模态参数识别方法研究

Output data only parameter identification is a challenge issue in the bridge health monitoring. The transmissibilty function is unique independent from excitation nature and location, while the strain mode is more sensitive to structural local damage. In this project, the strain power spectral transmissibility is conceived from measured dynamic strains. Based on the efficient computation and inherent property analysis of the strain power spectral transmissibility, a new strain modal parameter identification method is proposed for the bridge under operational conditions. The inherent properties of the strain power spectral transmissibility at the poles will be mathematically proved and the relationship between those inherent properties and strain modal parameter will be investigated. Regarding the measurement errors and spectral estimation leakage, an efficient algorithm will be proposed to select the window function and overlapping points for the purpose of improving the accuracy of strain power spectral transmissibility computation. Singular value decomposition technique will be used to strain power spectral transmissibility matrix to achieve the strain modal parameter identification. The stabilized diagram by using least square fitting in the frequency-domain is implemented to delete the false modes. The project is aimed at proposing a new strain modal identification method through the transmissibility. The outcomes will be served as a basis for the damage detection, health monitoring and assessment of bridges under operational conditions.

仅基于振动响应信号的参数识别是桥梁健康监测的发展方向，响应传递比函数具有不依赖于激励的性质和作用位置的优越特性，而应变模态对结构的局部损伤更为敏感。项目利用应变响应测量构建应变功率谱传递比，以应变功率谱传递比的固有特性分析和高精度计算为突破口，建立工作环境下桥梁结构应变模态参数识别新方法。项目需要从数学上严格证明应变功率谱传递比在系统极点处的固有特性，揭示其与应变模态的本质物理关系；针对测量误差和谱估计泄露的特点，在误差影响规律分析的基础上，提出高效算法选择窗函数和重叠点数等参数，从而提高应变功率谱传递比计算精度；充分利用应变功率谱传递比固有特性，研究基于应变功率谱传递比矩阵奇异值分解技术的应变模态参数识别算法；基于最小二乘频域法(LSCF)，绘制稳定图剔除虚假模态。项目旨在桥梁结构应变模态参数识别方法取得实质性突破，为更好的研究重大桥梁灾变机理、健康监测和安全评估提供基础和依据。

仅基于振动响应信号的参数识别是桥梁健康监测的发展方向，响应传递比函数具有不依赖于激励的性质和作用位置的优越特性，应变模态比传统的位移模态在结构损伤识别领域具有显著的优势，仅基于应变响应测试的工作应变模态参数识别，由于不需要对外激励的测试，更具有工程实用价值。项目利用应变响应测量构建应变功率谱传递比，以应变功率谱传递比的固有特性分析和高精度计算为突破口，建立了工作环境下桥梁结构应变模态参数识别新方法。选取一个应变响应测点作为参考点，定义了响应应变功率谱密度传递比（Strain Power Spectrum Density Transmissibility, SPSDT），从理论上证明了SPSDT在系统的极点处为应变振型系数之比，从数学上严格证明应变功率谱传递比在系统极点处的固有特性，揭示其与应变模态的本质物理关系；针对测量误差和谱估计泄露的特点，在误差影响规律分析的基础上，提出高效算法选择窗函数和重叠点数等参数，从而提高应变功率谱传递比计算精度；充分利用应变功率谱传递比固有特性，研究基于应变功率谱传递比矩阵奇异值分解技术的应变模态参数识别算法；基于最小二乘频域法(LSCF)，绘制稳定图剔除虚假模态。项目旨在桥梁结构应变模态参数识别方法取得实质性突破，为更好的研究重大桥梁灾变机理、健康监测和安全评估提供基础和依据。