PSI - Issue 58

Dipendra Gautam et al. / Procedia Structural Integrity 58 (2024) 102–108 D. Gautam et al. / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 6. MAC plot between the mode shapes extracted from 2019 and 2023 measurements.

4. Conclusions Using the parametric system identification technique, we present an insight into damage aggravation in a large masonry building damaged by the 2015 Gorkha, Nepal earthquake. We used a stable and noniterative state space system identification algorithm to estimate modal frequencies and mode shape vectors for two orthogonal directions and to assess the likely damage aggravation in the already damaged Ananda Niketan neoclassical building located in Lalitpur, Nepal. From the vibration records taken in 2019 and 2023, we obtained a sharp decrease in the frequency content along the damaged side of the building. The reduction in the first mode frequency is found to be around 44% and a significant reduction in vibration frequency is obtained for the higher mode frequencies as well. The frequency reduction along the short wall direction that observed significantly less damage is also significant, especially in the higher mode frequencies. A weak correlation between the mode shape vectors between the 2019 and 2023 measurements further justified that the building has sustained significant damage aggravation in five years. For further justification and damage aggravation quantification, sensors can be deployed permanently, and numerical models can be calibrated side by side. Also, damage localization can be performed by deploying many sensors at a time and synchronizing the vibration response. Acknowledgements We acknowledge the support provided by Rabindra Adhikari, Sajan KC, Gokarna Motra, and Arun Bikram Thapa. References Adhikari, R., Jha, P., Gautam, D., Fabbrocino, G., 2019. Seismic strengthening of the Bagh Durbar heritage building in Kathmandu following the Gorkha earthquake sequence. Buildings 9(5), 128. Allemang, R. J., Brown, D. L., 1982. Correlation coefficient for modal vector analysis, in “Proceedings of the First International Modal Analysis Conference and Exhibition”. Union College Press, New York, pp. 110-116.