Large area electronics based sensing sheet for strain monitoring and damage detection of bridges

Damage detection, localization and prognosis are fundamentally important for a comprehensive structural health monitoring (SHM) process. Damage is often associated with an anomalous strain changes or jumps. These changes are best captured if sensors are in direct contact with the damage. However, one-dimensional direct sensing is often expensive to cover the whole structure. Two-dimensional sensors, on the other hand, show promise to allow direct sensing on a large scale. Researchers at Princeton University have developed a flexible thin-film resistive strain sensor based on the principles on large area electronics (LAE). These two-dimensional sheets are suitable for covering large areas (≈10m²) and, hence, could be used for direct damage detection. In this work, the authors explore the suitability of such sheets for real-life applications. Results of laboratory experiments conducted using an aluminum cantilever beam for evaluation of performance in ideal conditions are presented. The strain measurements show an excellent match with analytical results with acceptable standard deviations. Strain measurements on Streicker Bridge at Princeton University campus obtained using these sheets are compared with those obtained from pre-installed fiber-optic sensors. The results show a close agreement between the two, inspiring confidence in the use of sensing sheets for cost-effective strain measurements and direct damage detection for long-term infrastructure structural health monitoring. Finally, the paper is concluded with limitations, sources of error and future possibilities.