A cost-effective approach for assessment of pre-stressing force in bridges using piezoelectric transducers

Electromechanical impedance (EMI) technique based health monitoring has emerged as a promising technique over conventional monitoring techniques in the last two decades. This paper presents an experimental and statistical investigation to monitor residual post-tensioning force in the pre-stressed reinforced concrete (PSC) bridge using piezoelectric patches through the EMI technique. Lead Zirconate Titanate (PZT) sensors were bonded on the commercial load cells and their EMI signatures were captured in the laboratory using an impedance analyser (E4980AL, Keysight) in the frequency range of 20 kHz to 250 kHz for different axial load values ranging from 0 ton to 42 tons. Assessment models were developed and validated in the laboratory for three PZT-based load cells. The calibrated PZT-based load cells were installed on a four-span continuous PSC bridge to estimate the externally applied post-tensioning force during its rehabilitation. EMI signatures were captured once the full load was applied on the post-tensioned cables and then after 24 h of loading. Using the developed assessment models and the mot mean square deviation (RMSD) values of the PZT-based load cells, the residual load in the post-tensioned cable was predicted and found a good agreement (overall error less than 14%) with that measured by the commercial load cell. This established the feasibility of a cost-effective approach of using inexpensive PZT-based load cells as an alternative to the well-established technique of using commercially available expensive load cells for the assessment of residual pre-stressing force during the increasing age of a prestressed concrete bridge.