Dynamic Identification and Damage Detection for a Greco-roman Monument

Dynamic identification is the process of the development of mathematical models for a system based on the vibration response. We considered a complex monumental building damaged by the 2015 Gorkha earthquake for system identification using ambient vibration records taken after the earthquake. The operational modal analysis technique implemented was carried out using Numerical Algorithm for Subspace State Space System Identification (N4SID). Ambient vibration records were taken in seven locations of the 113.26 × 85.27 m and 16.7 m tall monument initially constructed in 1910. The results of system identification highlighted that the first mode natural frequencies varied between 1.63–4.37 Hz for the seven setups, whereas the dominant vibration always occurred parallel to the short wall direction. The variation within a wing likely indicates the localized damage that was not morphologically identified. For a complex construction system such as Greco-Roman monuments without construction details, several sets of measurements are found to be more informative in terms of preliminary damage detection. We compared the results of system identification with the codal provisions to estimate vibration frequencies and found that the codal formulas give rise to a highly unrepresentative first mode frequency.