Structural assessment of a school building in Sankhu, Nepal damaged due to torsional response during the 2015 Gorkha earthquake

This paper discusses the structural assessment of a red-tagged four-story school building in Sankhu, Nepal. The building had a masonry-infilled reinforced concrete frame which was severely damaged during the 2015 Gorkha Earthquake. The concentration of damage in the west end of the first story indicates that the frame exhibited torsional response to the ground excitation. The authors visited the structure 2 months after the earthquake, collected LiDAR scans, and recorded the ambient vibrations of the damaged structure. The LiDAR data has been used to create a three-dimensional point cloud of the building which has allowed the identification of the locations and geometry of the major cracks but also the measurement of the permanent deformations of the building. The structure was also instrumented with four unidirectional accelerometers on every floor; two at opposite corners, to capture the translational and torsional motion. The translational and torsional modes have been identified with an operational modal analysis method and have been used to validate a finite element model of the structure. The comparison indicates that the model can capture the modal properties of the structure utilizing the strut modeling approach for the infill panels.