Back-analysis of the Collapse of a Tetrastyle Canopy during the April 25, 2015 Nepal Earthquake

Abstract

A monumental tetrastyle canopy (four columns topped by a hollow cap overlaying a statue), built in 1948 at the centre of Kathmandu, Nepal, has suffered full collapse during the April 25, 2015 Mw7.8 earthquake. Two video camera recordings let us recover the most important movements of the structure. At a distance of 2.9 km from the monument, an accelerometric station (KATNP) recorded the motion which we used as input of a model structure made with DEM. Geometry and dimensions of main elements were mostly obtained from satellite images. Concrete and steel in columns were considered as the common practice at that time. We performed some sensitivity analyses varying the mechanical properties due to the possibility of aging alterations in concrete and steel and to incorporate uncertainties on the geometric characteristics. Albeit the response has a significant variability, results show that it is possible to reproduce well the video images, attesting the importance of video cameras to capture the dynamic performance of structures, providing insight into their behaviour and data to support numerical investigations.