Structural Health Monitoring for the Assessment of the Dynamic Response of Existing Masonry Structures in Seismic Areas

摘要

Structural health monitoring is becoming increasingly popular in the field of construction management and maintenance of civil structures, especially those of strategic importance or relevant from a cultural heritage point of view. In Italy, through the national network of the Seismic Observatory of Structures (OSS), the Department of Civil Protection (DPC) monitors the oscillations caused by earthquakes in 160 constructions of public property. The paper reports the research activities performed on three monitored structures of the OSS, affected by the 2016 Central Italy earthquake swarm (max Mw=6,5). The three buildings (i.e. a school in Visso - MC, a former law court in Fabriano - AN and the city hall of Pizzoli - AQ) were constructed between 1920 and 1940 and are made of unreinforced masonry, with a good regularity in plan and elevation. Even though they present similar constructive features, the observed seismic-induced damages were largely different: heavy damages, near collapse, for Visso school; slightly damages for Pizzoli Municipality; and almost no damages for the building in Fabriano. The dynamic behavior of the monitored structures was studied through modal analysis techniques both under ambient vibrations and during the earthquake swarm. Data recorded by the monitoring systems are used to assess modal parameters variation and in particular to study the phenomenon of frequency and damping wandering during strong motion. Some severity indexes and dynamic parameters are calculated as well, including peak accelerations, structural amplifications, interstory drifts and elastic spectra. The results of modal identification will be used to assess the reliability of numerical models and their possible development to improve the predictive capacity in estimating the level of safety of existing structures.