Performance of Residential Buildings During M7.8 Gorkha (Nepal) Earthquake of April 25, 2015

Abstract eng:
The rapid urbanization has led to construction activities that often ignore long-term concerns of safety in extreme natural events such as earthquakes. These vulnerable structures add to the seismic risk of the region and have been responsible for losses and damages caused during the earthquake events. The M7.8 earthquake of 25th April, 2015 was a significant event in the long seismic history of the Eastern Himalayas which caused more than 8000 casualties, widespread destruction of residential, commercial and cultural heritage structures, surface fissures and landslides in the western and central regions of Nepal. It was followed by a strong aftershock of M7.3 after 17 days of the main event which caused further damages. These events provided a unique opportunity to study the vulnerability of the built environment and re-assess the risk exposure of the region which is undergoing rapid urbanization without adequate preparedness for seismic safety. A field trip was undertaken by the authors covering the affected regions of Nepal and adjoining Indian states of Uttar Pradesh and Bihar. This paper discusses the general observations in the earthquake-affected regions, with special emphasis on the seismic performance of masonry and concrete buildings in the Kathmandu valley region. The level of damage was consistent with the intensity of shaking experienced; however, some structures suffered dramatic collapse which could have been mitigated by good earthquake resistant practices. Widespread damage was observed in unreinforced masonry and reinforced concrete structures which lacked adequate lateral strength and seismic load resisting features. Lack of engineering input was evident from the poor structural and geometric configuration of the buildings and non-compliance with the building codes, which aggravated the seismic vulnerability of these structures. Cultural heritage structures, such as temples and palaces, were severely affected, as many of them were reduced to rubble. Since the maximum shaking intensity on Indian side was between V and VI, most structures did escape serious damage, but they continue to remain vulnerable for future design level earthquakes. Despite the knowledge of the high seismicity of the Himalayan region, the present lack of preparedness is unacceptable and it is necessary to implement good earthquake resistant practices to minimize losses in future earthquakes.

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