Monitoring system of buildings with high vulnerability in presence of slow ground deformations (The Campi Flegrei, Italy, case)

Abstract

In this work we illustrate the results of some laboratory and full scale experiments which have the purposes of analysing the performance of different types of monitoring equipments in detection of damage level in masonry buildings. Such experiments involved monitoring, by means of optical fibre strain-metre and total laser station, of a selected building that, owing to its position in the active caldera of the Campi Flegrei (Southern Italy), could undergo remarkable ground shaking and large, although very slow, ground movements (bradyseismic crises) of volcanic origin. The field geodetic monitoring has been realised by an automatic system of topographical 3D survey, based on two automatic Total Station Leica TCA2003 and by increasing the number of benchmarks of the levelling network in the area near the building. The experiments have shown that structure deformations caused by elastic phase, when the building undergoes elastic deformation, is close or under the limit of detection through laser total station (about 1–2 mm), while, when the damage occurs, deformations increase up to values beyond 10–20 mm easily detectable by geodetic methods. The optical fibre monitoring provides good results in elastic phase, whereas as the damage level rises up the data become more and more difficult to understand. In conclusion the paper shows that the geodetic techniques are very useful in structural quasi real-time monitoring for analysing the behaviour of masonry buildings damaged by ground movements induced by landslide phenomena, bradyseism or intrinsic structural yielding.