Browsing by Author "Liu, Fangyu"

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    Condition Assessment of Civil Infrastructure and Materials Using Deep Learning
    Liu, Fangyu (Virginia Tech, 2022-08-24)
    The abilities of powerful regression and multi-type data processing allow deep learning to effectively and accurately complete multi-tasks, which is the need of civil engineering. More cases showed that deep learning has become a greatly powerful and increasingly popular tool for civil engineering. Based on these, this dissertation developed deep learning studies for the condition assessment of civil infrastructure and materials. This dissertation included five main works: (1) Deep learning and infrared thermography for asphalt pavement crack severity classification. This work focused on longitudinal or transverse cracking. This work first built a dataset with four severity levels (no, low-severity, medium-severity, and high-severity) and three image types (visible, infrared, and fusion). Then this work applied the convolutional neural network (CNN) to classify the crack severity based on two strategies deep learning from scratch and transfer learning). This work also investigated the effect of image types on the accuracy of these two strategies and on the classification of different severity levels. (2) Asphalt pavement crack detection based on convolutional neural network and infrared thermography. This work first built an open dataset with three image types (visible, infrared, and fusion) and different conditions (single, multi, thin, and thick cracks; clean, rough, light, and dark backgrounds) and periods (morning, noon, and dusk). Then this work evaluated the performance of the CNN model based on the accuracy and complexity (computational and model). (3) An artificial neural network model on tensile behavior of hybrid steel-PVA fiber reinforced concrete containing fly ash and slag powder. This work considered a total of 23 factors for predicting the tensile behavior of hybrid fiber reinforced concrete (HFRC), including fibers' characteristics, mechanical properties of plain concrete, and concrete composition. Then this work compared the performance of the artificial neural network (ANN) method and the traditional equation-based method in terms of predicting the tensile stress, tensile strength, and strain corresponding to tensile strength. (4) Deep transfer learning-based vehicle classification by asphalt pavement vibration. This work first applied the pavement vibration IoT monitoring system to collect raw vibration signals and performed the wavelet transform to obtain denoised vibration signals. Then this work represented the vibration signals in two different ways, including the time-domain graph and the time-frequency graph. Finally, this work proposed two deep transfer learning-based vehicle classification methods according to these two representations of vibration signals. (5) Physical-informed long short-term memory (PI-LSTM) network for data-driven structural response modeling. This work first applied the single-degree-of-freedom (SDOF) system to investigate the performance of the proposed PI-LSTM network compared with the existing methods. Then this work further investigated and validated the proposed PI-LSTM network in terms of the experimental results of one six-story building and the numerical simulation results of another six-story building.