System Identification and Damage Detection of Beam-like Structure Under Moving Vehicles Using SSI-WPT Method

• Main Authors: Tzu-Yun Hung, 洪慈韻
• Other Authors: Chin-Hsiung Loh
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/r2s9c5

碩士 === 國立臺灣大學 === 土木工程學研究所 === 103 === Application of system identification technique, known as Covariance-driven stochastic subspace identification (SSI-COV), cooperated with Wavelet packet transform (WPT), to identify the dynamic characteristics of bridge under bridge-vehicle interaction with considering random road surface roughness. In the first portion of this study, numerical simulation of a two-span continuous bridge using finite element model is presented with the consideration of bridge-vehicle interaction and road roughness. From the response signal collected in different locations, SSI-COV was applied to identify the bridge vibration frequencies. In order to eliminate spurious poles due to the tuned effect of bridge and vehicle vibration phenomenon, wavelet packet transform was used to reconstruct signals of possible spurious modes and observed the phase difference among the measurements. The second part of this study is using the proposed SSI-COV method to identify the dynamic characteristics of a bridge in its operating condition: Guan-du Bridge. Discussion on the stability diagram from different measurement time is discussed. In addition, damage detection of bridge-like structure are also proposed: (1) Subspace-Null space damage indices (DIn、DIs、DI), (2) Hilbert Amplitude Assurance Correlation, and (3) Change in system flexibility. Through numerical simulation of damage scenarios: (1) Stiffness reduction in one of the bridge element, (2) Stiffness reduction on the bridge bearing system, the proposed damage indices were applied for damage assessment of the bridge.