Residential RC Building Damage Trends After 2015 Nepal Earthquake

Abstract eng:
The Mw 7.9 Nepal Earthquake at AM11：56, April 25, 2015 (also known as the Gorkha Earthquake) resulted in a lot of injured people and caused numerous buildings, including world heritage sites, to collapse. In its aftermath, damage investigations were conducted around the nation’s capital of Kathmandu Metropolitan City and Lalitpur Sub-Metropolitan City (commonly referred to as Patan). In the course of our investigation, 21 reinforced concrete (RC) residential buildings that were more than 10 floors high were examined. Some of these were under construction when the earthquake occurred. The investigation process included visual examinations, listening surveys, quick post-earthquake inspections for damaged buildings, and natural period evaluations based on microtremor measurements. This report begins with a presentation on our study objectives and the characteristics of RC high-rise residential buildings in Nepal, after which a summary of damage trends is provided. Our results show that while most of the RC frame structures examined suffered minor damage, more significant destruction was found in nonstructural infill brick walls both inside and outside inspected buildings. Damage types included shear failures as well as cracks along the masonry joints and boundary surfaces between RC frames and brick walls. It was also found that damage levels tended to be more severe in the lower floors than the upper floors. The same tendencies were noted in Japan when comparisons were made to building damage during the Great East Japan Earthquake, which occurred on the Pacific coast of the Tohoku region on March 11, 2011. Specifically, damage levels inside high-rise buildings were found to be more severe than could be seen from the outside, while numerous low-rise buildings in the examined areas showed no damage at all. Additionally, damage was found in buildings equipped with expansion joints that seemed to be caused by pounding behavior resulting from inadequate expansion joint clearance. Next, because existing methods tend to underestimate damage levels, an original method of conducting quick post-earthquake inspection of damaged buildings was proposed. It is believed that life continuity plans based on the results obtained via our original method would more closely match actual damage levels. In addition, microtremor vibration observations were carried out in seven buildings, one of which had no installed non-structural walls because it was under construction at the time, and vibration properties were evaluated based on the results of those observations.

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