Built in 1964-65, 105 The Terrace is a 23-story, 68-metre tall building in central Wellington. This structure features a unique composite design with concrete encased steel lattice columns, a 7-story podium, 16-story tower, and 3-story penthouse. Initial seismic assessments suggested a need for extensive retrofitting, including mid-height base isolation. This conservative approach was estimated to cost approximately 20 million USD and posed significant challenges for building functionality and occupant disruption. Based on the PBE findings, Miyamoto developed a targeted retrofit strategy involving steel jacketing of columns between levels 6 and 8 and installation of 4 viscous dampers on each side of the building at critical levels. This approach resulted in a dramatic reduction in retrofit costs from 20 million to 5 million USD, representing a 75% savings.
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