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Numerical and experimental studies on the extraction of bridge mode shapes using vehicle response
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School of Engineering |
Master's thesis
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en
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93
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Over the past two decades, the Vehicle Scanning Method (VSM) has become a cost-effective and scalable approach for assessing bridge condition, offering a potential alternative to conventional monitoring systems. VSM utilizes moving vehicles equipped with a small number of sensors to capture high-resolution spatial information across the structure. This thesis proposes a VSM-based method for extracting bridge mode shapes and systematically evaluates its performance through numerical simulations, laboratory experiments, and field tests. The vehicle dynamic response obtained during vehicle passage on a bridge is processed using the Fast Fourier Transform (FFT) to extract the bridge’s modal frequencies. Bandpass filtering is then applied to isolate individual bridge vibration modes, and the corresponding mode shapes are reconstructed using both Hilbert Transform (HT) and Wavelet Transform (WT). Several parametric studies are carried out to assess the method’s sensitivity to key factors, such as vehicle speed, vehicle damping, bridge damping, environmental noise, and road roughness. The results indicate that the proposed method performs most reliably under low vehicle speeds, minimal bridge damping, and negligible dynamic interference. Experimental validation on a scaled steel simply supported bridge and an operational cable-stayed bridge confirms the method’s practical potential, especially when the vehicle maintains a constant speed and exhibits stable movement. Across all scenarios, WT consistently outperforms HT, demonstrating its superior accuracy for VSM-based modal identification.