Laboratory investigation of sensors reliability to allow their incorporation in a real-time road pavement monitoring system

Abstract

Unlike other engineering structures, road pavements have a greater monitoring complexity due to their heterogeneous composition and the diverse and increasing loads they are subjected to, hindering the preventive maintenance operations. For that reason, real-time monitoring systems are extremely useful to measure strains/displacements and temperature. Most of the currently applied systems use electric sensors, known as strain gauges, but a new monitoring technology has gained popularity in the last decades. Fibre Bragg grating (FBG) is an optical sensor with great potential that has been introduced on monitoring systems. The attempts to include FBG sensors in pavement monitoring have shown that further investigation is needed. Some factors to be studied are the interaction between the sensor and pavement, the use of coatings, the application method, and the influence of external conditions (e.g., temperature). This article presents preliminary laboratory work on FBG optical sensors vs electric sensors as part of the Rev@Construction project that aims to digitalise the construction industry in Portugal. This work will be essential to assure the reliability of FBG sensors before they are installed in a pavement monitoring system for a highway section. Through a series of controlled strain tests in a four-point bending apparatus, it was possible to conclude that the FBG sensors have a better quality signal than electrical strain gauge (SG) sensors. Furthermore, FBG sensors are not affected by magnetic fields, a clear advantage compared to SG sensors. The importance of temperature calibration on FBG sensors was also demonstrated in this work when analysing the data collected.