Identifying damage mechanisms of gymnasium structure damaged by the 2011 Tohoku earthquake based on biaxial excitation

During the 2011 Tohoku Earthquake, gymnasium buildings sustained unexpected structural damage, preventing their use as evacuation shelters. This study examines one such severely damaged structure with fewer connections between steel roof and reinforced concrete columns. Results of eigenvalue, pushover, seismic response analyses elucidate observed damage. The out-of-plane deformation is prominent because slight constraint at column top, leading to severe damage base. Moreover, a parametric peak ground acceleration suggests that biaxial excitation produces different failure modes top from those under uniaxial excitation. variation mechanisms evidenced by variety motions broad range frequency characteristics. Pushover analysis results demonstrated predictability initial connection failure. However, discrepancies pushover became greater subsequent failures. base can be assessed accurately based on analyses.