Comparison between point and long-gage FBG-based strain sensors during a railway bridge load test

Strain is a key parameter in laboratory and bridge load testing. The selection of a strain sensor depends on several factors, including the aim of the test and the specimen material. The application of the right sensor is vital to obtain accurate readings, especially in the case of heterogeneous materials such as concrete. This paper focuses on long-gage and point fiber Bragg grating-based strain sensors and their possible applications on concrete elements. First, strain sensors are described, after which long-gage and point fiber Bragg grating strain sensors are compared in a concrete specimen test, a concrete column test and static and dynamic load tests on a concrete railway bridge. Results show that although it is advisable to use long-gage sensors when monitoring heterogeneous materials, there are some particular cases were both sensors type can provide accurate strain measurements.