Field Evaluation of Sensing Sheet Prototype Exposed to Cracking

Reliable crack detection and characterization is challenging. Sparsely spaced discrete strain sensors are insensitive to cracks if placed at even modest distances from damage. Improving spatial density of sensors significantly improves reliability in crack detection and characterization, but also significantly increases the costs associated with hardware, sensor installation, and data analysis and management. In the case of very large structures, one-dimensional distributed fiber optic sensors can be applied with reasonable costs, and while they significantly improve reliability in crack detection and characterization, they still cover only one dimension of a structure. In order to address the above challenges, two-dimensional sensor, called sensing sheet, have been developed. It consists of dense array of discrete sensors patterned over thin-film substrate, with integrated computational and power management circuits. The aim of this paper is to present field test performed on the sensing part of sensing sheet and evaluate its performance in crack detection and characterization in real-life settings. Two prototypes of sensing sheet were manufactured and tested. Each of them consisted of eight discrete full-bridge resistive strain sensors. One prototype was installed on the underside of the superstructure of a deck stiffened arch and the other over existing shrinkage cracks on the foundation of Streicker Bridge. The behavior of the sensors was observed under daily temperature change. The test confirmed applicability of sensing sheet in real-life settings and its excellent performance in crack detection and characterization.