FINITE ELEMENT MODELING AND UPDATING OF A FIVE-TIERED PAGODA STYLE TEMPLE

Historical pagoda style temples demonstrate different dynamic behavior than traditional unreinforced masonry (URM) structures due to the unique construction practices and ornate architectural detailing. Recently, the 2015 Gorkha Mw 7.8 earthquake resulted in widespread structural damage and collapse of similar historic temples in Nepal. However, one temple did not collapse. This is the five-tiered pagoda style Nyatapola temple built in 1702 and located in Bhaktapur, Nepal. Understanding the seismic vulnerability and structural behavior of these pagoda-style temples can lead to more efficient retrofit solutions and conservation practices for similar heritage structures. This study developed and calibrated the pre- and post-earthquake finite element (FE) models of the Nyatapola temple that are based on post-earthquake reconnaissance efforts. This includes lidar data, visual damage assessment, and ambient vibration test results. A detailed linear time history analysis is conducted to simulate the seismic demands during the 2015 event, and give insight into the performance of pagoda style temples for future seismic events. The pre-earthquake fundamental frequency of 1.68 Hz is higher than similar Nepali temples, indicating the usually stiff behavior of this temple. The eigenvalue analyses on the calibrated finite element models demonstrated an 11% reduction in fundamental frequency between the pre- and post-earthquake states. This frequency shift indicates a significant reduction of structural stiffness, as evident in the observed post-earthquake shear cracking. Linear time history analysis results demonstrated maximum displacement and acceleration demands of 67 mm and 0.6 g respectively, under the bi-directional aftershock record pair (Mw 7.3). For this structure, this aftershock record produced the largest seismic demands on the structure. Significant damage to the earthen URM walls of the Nyatapola temple was observed and is likely a result of induced torsion and poor structural detailing between the wall wythes or layers. Accordingly, this study recommends that strength-based retrofit schemes may be able to increase the connectivity between the wall layers and subsequently reduce future damage to pagoda style structures. These retrofit schemes are anticipated to enhance the resilience of these heritage structures. Advisor: Richard L. Woo