Allowing for second-order effects in New Zealand design

In design for the ultimate limit state, the New Zealand Loadings Standard requires second-order effects to be considered at the analysis stage of structural design and requires the most adverse distribution of variable gravity loading to be considered for load combinations involving gravity loading alone. New Zealand is a seismically active country and, when designing seismic-resisting systems, second-order effects for both seismic and non-seismic load conditions must be considered. This paper provides a brief and general overview of New Zealand practice in these areas, with reference to design of rigid moment-resisting sway frames (MRSFs). These systems are chosen because they most clearly highlight the differences required between seismic and non-seismic conditions. Reference to the appropriate clauses of design standards and to other relevant sources of design guidance are given.