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

Abstract

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.