Improving the Nepalese Building Code Based on Lessons Learned From the 2015 M7.8 Gorkha Earthquake

The evaluation of the damage and impact after disastrous events offers a unique learning opportunity to improve existing earthquake risk reduction measures or implement new strategies. Damage observations and building surveys after the 2015 M7.8 Gorkha earthquake revealed structural deficiencies in low-rise reinforced concrete (RC) buildings with masonry infills, which are the prevalent building type in urban areas in Nepal. In particular, statistical analyses from damage data of more than 100 RC buildings have indicated a strong correlation between a wall index (WI) and damage level, which is a structural feature not currently controlled by the Nepal Building Code. This correlation was analytically verified through nonlinear dynamic analyses considering four typical Nepalese RC buildings with increasing WI levels. These analytical results were combined with a seismic hazard model for Nepal to calculate the distribution of the average annual collapse probability across the country. The findings of the study were used to provide recommendations concerning the minimum WI that could be incorporated by the building code.