In situ monitoring on prestress losses in the reinforced structure with fiber-optic sensors

Measurement and evaluation of the prestress losses in the reinforced structures are essential issues for structural design and healthy assessment. In the present work, an optical-fiber-sensor-based monitoring technique was introduced to evaluate the prestress loss quantitatively in the steel-strand reinforced structures. A total of 14 fiber-optic sensors were employed and fixed on the steel-strand through the pre-designed windows on a sewage treating tank. The output signals were collected and analyzed via the secondary meters and computer. Results indicate that the optical-fiber-sensor-based system is feasible for on-line monitoring of the prestress losses of the reinforced concrete structures in practice. The value of the short-term prestress loss is apparently related to the arrangement of steel strand in concrete. For the measured sewage treating tank, the value of prestress loss due to deformation of anchor is greater than that due to relaxation of steel–strand during ten days after tensioning. The whole loss of prestress due to relaxation, deformation and creep at point A is only 1.4% after ten days since tensioning.