100^th Anniversary of the Monitoring of Stevenson Creek Experimental Dam: Reflections on the Past and Future Advancements on Strain Sensing and Strain-Based Monitoring of Civil Structure

Stevenson Creek Experimental Dam was bult near Fresno, California, in 1924-1925, with the aim of studying the structural behavior of arch concrete dams. To achieve the project objectives, six types of sensors were deployed: four types of sensors were based on mechanical devices that were operated manually, but two novel types of sensors, deflection (relative displacement) sensors and embeddable strain sensors (consisting of a stack of carbon discs), were both based on electrical resistance and were assessed remotely, via wires. While the use of mechanical manual sensor technologies in real-life applications can be traced back to the 19th century, what makes the application of novel sensors in Stevenson Creek Experimental Dam paradigm changing, is the fact that the readings of resistive deflection (relative displacement) and strain sensors were performed from a remote room. The centenary of this technological achievement, which represents the first application of modern monitoring technique in the United States of America (to the author’s best knowledge), stimulates reflection on the past accomplishments and the future advancements on strain sensing and strain-based monitoring of civil structures. Hence, the aim of this paper is to summarize the progress in strain sensing technologies and their impact on strain-based monitoring over the first hundred years, and to give a few glimpses about directions of future developments.