Advancing Structural Understanding: System Identification of Steel Plate Girder Bridges in Nepal

Efficient infrastructure management relies on accurate bridge system identification, crucial for societal well-being and economic prosperity. This research pioneers a method to determine the fundamental frequency of steel plate girder bridges using smartphone accelerometers and Finite Element Method (FEM) modelling. Conducted along the East-West Highway in Nepal, this study focuses on 12 motorable bridges, employing the Android app Phyphox to gather vibration data induced by highway traffic. By applying operational modal analysis and peak picking techniques, the natural frequencies of these bridges are pinpointed, while a detailed FEM model in SAP2000 aids in correlating field observations. Notably, the study reveals that a bridge's span significantly influences its frequency, with longer spans exhibiting lower frequencies and vice versa. Close alignment between FEM predictions and smartphone-acquired data underscores the method's reliability, with disparities generally limited to 10%, primarily attributed to simplifications in modelling assumptions. Moreover, the investigation identifies structural issues like girder cracks on Pasaha Bridge, elucidating instances where field observations diverge from FEM predictions. This comprehensive approach not only enhances our understanding of bridge dynamics but also furnishes invaluable insights for maintenance and infrastructure planning, essential for ensuring the longevity and safety of critical transportation networks.