Concise Historic Overview of Strain Sensors Used in the Monitoring of Civil Structures: The First One Hundred Years

Abstract

Strain is one of the most frequently monitored parameters in civil structural health monitoring (SHM) applications, and strain-based approaches were among the first to be explored and applied in SHM. There are multiple reasons why strain plays such an important role in SHM: strain is directly related to stress and deflection, which reflect structural performance, safety, and serviceability. Strain field anomalies are frequently indicators of unusual structural behaviors (e.g., damage or deterioration). Hence, the earliest concepts of strain sensing were explored in the mid-XIX century, the first effective strain sensor appeared in 1919, and the first onsite applications followed in the 1920′s. Today, one hundred years after the first developments, two generations of strain sensors, based on electrical and fiber-optic principles, firmly reached market maturity and established themselves as reliable tools applied in strain-based SHM. Along with sensor developments, the application methods evolved: the first generation of discrete sensors featured a short gauge length and provided a basis for local material monitoring; the second generation greatly extended the applicability and effectiveness of strain-based SHM by providing long gauge and one-dimensional (1D) distributed sensing, thus enabling global structural and integrity monitoring. Current research focuses on a third generation of strain sensors for two-dimensional (2D) distributed and quasi-distributed sensing, based on new advanced technologies. On the occasion of strain sensing centenary, and as an homage to all researchers, practitioners, and educators who contributed to strain-based SHM, this paper presents an overview of the first one hundred years of strain sensing technological progress, with the objective to identify relevant transformative milestones and indicate possible future research directions.

A Systematic Review of Optimization Algorithms for Structural Health Monitoring and Optimal Sensor Placement

“…Over the years, researchers have developed a variety of sensors suitable for SHM based on the latest advances in sensor technology. Generally, sensors in SHM systems fall into two categories: advanced [ 96 ] and conventional [ 97 ]. The most widely used sensors for SHM include fiber optic sensors (FOSs), accelerometers, vibrating wire traducers, linear variable differential transformers (LVDTs), load cells, strain gauges, inclinometers (slope indicators), tiltmeters, acoustic emission sensors, microelectromechanical systems (MEMSs), and temperature sensors.…”

Structural health monitoring of inland navigation structures and ports: a review on developments and challenges

“…70 Strain can also be measured using vibrating wire SGs (VWSGs), which are based on the change in the vibrating frequency of tensioned wire. 71…”

“…70 Strain can also be measured using vibrating wire SGs (VWSGs), which are based on the change in the vibrating frequency of tensioned wire. 71 Accelerometers are used to measure motions of a body with the respect to an inertial reference frame. In principle, they have a seismic mass that moves with the motion, a transducer element (e.g., Piezoelectric) attached to the mass, and measuring electrodes.…”

Piezoelectric Materials and Sensors for Structural Health Monitoring: Fundamental Aspects, Current Status, and Future Perspectives

“…Sensors with high sensitivity, good reliability, and low cost are the cornerstone for the structural health monitoring (SHM). Various kinds of sensors have been developed to realize the SHM, such as strain gages [ 5 ], accelerometers [ 6 ], fiber optical sensors [ 7 , 8 ], displacement sensors [ 9 ], piezoelectric sensors [ 10 ], and laser Doppler vibrometers [ 11 ]. Piezoelectric materials are capable of becoming electrically polarized upon the application of external stress or deform in response to electrical stimuli.…”