Analytical Study of Structural Health Monitoring Using Piezoelectric Ultrasonic Guided Waves for Bridge Infrastructure in Benue State

Bridge infrastructure in Benue State, North Central Nigeria, is subjected to significant structural stress from seasonal flooding, heavy truck loading on agricultural commodity transport routes, and deferred maintenance, creating a need for reliable structural health monitoring systems that can detect damage accumulation before catastrophic failure. This study presents an analytical and experimental investigation of piezoelectric transducer-based ultrasonic guided wave structural health monitoring for steel bridge girders in Benue State. A network of PZT piezoelectric wafer active sensors is bonded to three instrumented steel I-beam specimens representing bridge girder cross sections typical of the Benue River bridge inventory. Lamb wave propagation signals are excited and received across sensor paths, and signal processing algorithms including continuous wavelet transform and baseline subtraction are applied to detect and localize introduced defects including notches and simulated crack growth. The detection sensitivity of the guided wave SHM approach is quantified as a function of defect size, defect location relative to sensor network geometry, and temperature variation. Defects with area exceeding 40 square millimetres are detected with 95 percent probability at temperatures between 20 and 40 degrees Celsius. A compensation algorithm for temperature-induced baseline signal drift is developed and validated. An outdoor pilot monitoring installation is implemented on the Makurdi River Road bridge approach span, and continuous data collection over three months confirms the system's operational stability under field environmental conditions. Keywords: structural health monitoring, piezoelectric, guided waves, bridge inspection, Benue State