Description
Rayleigh based fiber optic sensing enables quasi-continuous strain measurements with high spatial resolution over extended ranges up to 100 m per sensor. The dense strain readings provide valuable insights into the structure, both locally and globally. On the global scale, deformation and load redistribution within a structure can be observed. On the local scale, even the smallest cracks, with widths below the human perception range can be detected. The durability of concrete structures depends to a large extent on the existing crack widths. Hence, early age monitoring of structures can have a decisive influence on the long-term infrastructure maintenance costs. The distributed nature of distributed fiber optic sensors (DFOS) enables monitoring of concrete structures from the beginning of their existence, where the precise locations of future damages are not known. Deployment of DFOS into the formwork enables monitoring the (precast) concrete structure through all production stages, from pouring, its curing phase, through stripping the formwork, prestressing, transport, up to its montage on site. Used for quality control, manufacturers can harness this early age monitoring for internal quality control or even proof the agreed quality to the owner by issuing birth certificates.
As part of the IDA-KI research project, a large-scale demonstrator bridge – the openLAB – is built with precast girders. These are equipped with an extensive monitoring system, including cast-in DFOS. Preliminary tests are carried out on 15 m long prestressed precast elements, before the final assembly of the bridge. In this contribution, we present some results of experiments on these large-scale specimens.
