Kalymnos island power station, Hellenic P.P.C.

The power station’s main building was constructed in the mid 70s from reinforced concrete. It is of rectangular shape 42.0 by 35.5 meters. There is also a 15 meter long crane carrier across the building’s main span. In 2013, three columns were reinforced with shotcrete (gunite).

To cover the needs of the buildings reinforced bearing skeleton static and dynamic analysis, CRD Group installed a structural monitoring system consisting of 31 strain FBG (Fiber Bragg Grating) optical sensors.

The sensors were installed on the structure’s most critical points (maximum stress or strain). These positions were chosen on three main structural frames, in order for the main columns’, beams’ and crane carrier beams’ measurements to be comparable and symmetrical. Sensors were placed both on the old concrete, inside the shotcrete and on top of it.

The sensors’ spectral response was completely satisfactory, even on those undergone the shotcrete work’s stress. For the sensors layouts’ data acquisition, CRD Group utilized its own sensor monitoring software.

Measurements were taken during several crane carrier’s crossings (dead load only). A noteworthy change of strain was recorded from the crane carrier beam sensors. This fact is due to the old structural members’ lesser stiffness, because of old material quality and richer crack network. The newly reinforced columns showed smaller strain, as expected. As a conclusion, the structure’s monitoring indicates the good quality of the structural reinforcing (shotcrete works).