Detection of Local Buckling in Thin-Walled Hollow Structural Steel Sections Using Fibre Optic Cables

Fibre optic cable-based techniques have recently been introduced in the steel construction industry. This is due to their high sensitivity, ability to resist electromagnetic interference, be lightweight and efficiently multiplex. However, fibre optic cable sensors are still limited due to their initial high cost and unfamiliarity to the users. This paper compares fibre optic cable sensors to traditional strain gauge sensors via an experimental program comprising four-point bending and three-point bending tests. The sensors were used to detect the location and initiation of local buckling in thin-walled polygonal hollow section (PHS) and rectangular hollow section (RHS) beams. The results showed that for these deep thin-walled beams with similar cross-sectional dimensions, the PHS beams were able to reach their yield moment capacities, while the RHS beams failed due to local buckling at about 40% below their yield moment capacities. In addition, unlike the strain gauges, the fibre optic cable sensors were able to detect the location and initiation of local buckling along the length of the tested beams.