ROC analysis-based optimal design of a spatio-temporal online seismic monitoring system for precast industrial buildings

The aim of this work is to propose an efficient tool for the design of the monitoring system of precast reinforced concrete industrial buildings in seismic hazard zones, enabling the rapid post-earthquake damage assessment. The methodology, designated as spatio-temporal online monitoring (STOM) is performed by analyzing data obtained from a set of bi-directional accelerometers integrated in smart columns within the building. Acceleration records are converted into inter-story drift ratio (IDR) data, designated as engineering demand parameters, by double integration. Then, calculated IDRs are compared to three levels of alert thresholds meaning that, for the selected damage state, the structure is classified as apparently safe, restricted use or unsafe, corresponding to slight damage, moderate damage and severe damage. Finally, the STOM results trigger visual inspections, thus representing the main inputs needed by engineers in order to evaluate the structural health status and eventually decide for further actions. Measurements data are collected across time as well as space to ensure greater robustness and effectiveness. The STOM methodology allows the preliminary design, i.e., number and location of sensors and optimal demand thresholds, by exploiting the receiver operating characteristics (ROC) analysis, which classifies the different options on the basis of their performance in reporting true damage scenarios with respect to false alarms. Hence, seismic monitoring data are used in conjunction with the pre-evaluated alert states as an engineering decision-support tool for the post-earthquake diagnosis of the structure.