Preliminary analysis of instrumented Wellington building responses in the July/August 2013 Seddon/Lake Grassmere earthquakes

This paper investigates the dynamic response of five instrumented structures in the greater Wellington region during the July/August 2013 Seddon/Lake Grassmere earthquakes. Six events ranging from Mw 5.6 6.6 were considered in the analysis of five different structures: GNS Science at Avalon, BNZ Centre Port, Majestic Centre, Victoria University Te Puni Village Tower, and Wellington Hospital. This preliminary investigation firstly involved determination of the fundamental period of each structure in the principal horizontal directions, and comparison with the simplified method proposed in NZS1170.5:2004. Secondly, the peak floor level acceleration distributions over the height of the structures were analysed and compared with the design provisions in NZS1170.5:2004 and ASCE/SEI7:2010., The results illustrate that the simplified equation for fundamental period in NZS1170.5:2004 often underestimated the fundamental period and could result with unconservative design forces when using forced based design, and that both NZS1170.5:2004 and ASCE/SEI7:2010 provisions for floor acceleration contain significant deficiencies due to the omission of the dependence of peak floor acceleration variation with height on vibration period.