This article presents a study of the seismic behavior of the Old Municipal Chambers building in Christchurch, which was damaged by earthquakes in 2010 and 2011. In view of its seismic vulnerability and retrofitting, finite element and equivalent frame models were used for pushover analysis. Predictions allow identifying the weak parts of the building and its expected failure modes, which are in agreement with the observed damage. Computations seem conservative, however, because the building capacity curves provide insufficient strength to survive the registered earthquakes. By considering the floors as bidirectional diaphragms in the simplified model, a better behavior is observed. © 2013 A. S. Elnashai & N. N. Ambraseys.