H. Kit Miyamoto (1) and Amir SJ Gilani (2)
(1) President, Miyamoto International, Inc.
(2) Manager Earthquake Engineering, Miyamoto International, Inc.
The magnitude-7.8 earthquake on April 25, 2015 and its many aftershocks, including the magnitude-7.3 aftershock on May 12, 2015, caused massive damage to the built environment in Nepal. Near the epicenter, it had a maximum Mercalli Intensity (MMI) of IX. It is estimated that it caused over 9000 fatalities and resulted in more than 20000 injuries. The cost associated with the earthquake is estimated at roughly $US 5B, which is nearly a quarter of Nepal’s GDP. This event is considered the worst natural disaster in Nepal in the past eight decades. In Katmandu, which is far from the epicenter, it is noted that the maximum peak ground acceleration was order of 0.15 g. However, the response spectrum has a pronounced peak at the high period portion of the spectrum. The large spectral acceleration at periods of 2 to 5 sec caused significant damage to midrise to tall buildings (with characteristic period in the range of ground motion amplified response.). In the aftermath of the earthquake, the authors surveyed survey the damage for two areas for importance of national agenda, tourism: the Everest and Annapurna regions. It is estimated that these regions experienced PGA of 0.1 g or less. ATC 20 (ATC 1987) methodology was used for the rapid assessment. This was followed by seismic retrofit design of modern midrise buildings damaged in the earthquake. For a number of buildings, seismic viscous dampers were selected as the retrofit option. These buildings served as the first application of passive energy dissipation in Nepal
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