A long-term static monitoring experiment on R.C. beams: damage identification under environmental effect

The authors have been conducting a static continuous monitoring experiment to assess the validity of some damage detection algorithms, consisting in non-model-based statistical data processing, previously validated, even for small levels of damage, on numerically simulated 2D finite element models of simply supported and continuous beams. Tests have been conducted in Italy on two specimens of pre-stressed R.C. beams equipped with fibre optic strain sensors and temperature sensors and placed outdoor. During the tests, several events have been artificially produced: a ballast load has been positioned on the beams and various known levels of damage have been introduced. One of the two beams was kept intact for reference. Preliminary data processing has disclosed substantial differences between the numerical simulations and the measurements obtained on the field for the case of simply supported beams. This paper shows that environmental variations have a great effect on measurements and should be correctly removed from the strain time histories before a reliable damage detection procedure can be successfully applied.