SEISMIC DAMAGES OF RC FRAMES IN NEPAL MS 8.1 EARTHQUAKE

A half-month seismic reconnaissance survey has been conducted two months after Nepal Ms. 8.1 earthquake. This paper reports the seismic hazards observed in reinforcement concrete (RC) frame structures at three sites. Only a few important RC frame buildings are anti-earthquake designed, such as hospitals, government buildings and schools, while the rest are non-engineered residential buildings and commercial buildings. All these RC frames were casted in-site, and the infilled walls are clay brick masonries. Typical damages include compression-flexure combined failure in the first storey or in the storey parallel with the street, cracking and collapse of infilled masonry walls, damages close to construction joint in columns and beam-to-column joints, shear failure of the columns due to adjacent infilled walls, falling of the parapet, and total collapse of several RC frames. Detailed survey was given to six damaged RC frames in Charikot, with dimensions, material strength, and failure modes being physically measured and acquired. It is shown that a good seismic performance is always associated with frames having smaller axial force ratios and larger stiffness-to-weight ratios. Finally, considering the measures stipulated in Chinese seismic design codes and seismic hazards in recent strong earthquakes, it is necessary to prevent RC frames from shear failures, nonstructural damages and collapses, while safety assessment after earthquake are also discussed.