Reflections on New Zealand's earthquake resistant design approach

Perceived shortcomings in NZS 1170.5 [1] and some other Standards are highlighted and areas for improvement are suggested. A particular focus is placed on achieving the principal objective of achieving life safety at the limit state at which structural collapse is to be avoided. Topic areas commented on include:

The objectives of earthquake resistant design, especially that of avoiding the collapse of structures

The appropriateness of current classifications of buildings into importance levels

The currency and adequacy of the design seismic hazard spectra requirements

The justification for, and application of, a structural performance factor

The force-based and displacement-based methods of analysis and design, and the effects of plastic hinging relieving member permanent load moments at plastic hinges adjacent to points of support

Consideration of displacement effects, and effects on displacements, at the limit state at which collapse is to be avoided

Achieving reparability

Some shortcomings in the material Standards for both structural steel and reinforcing steel

Consideration of site conditions, and in coastal locations the tsunami risk

Comparability of New Zealand design requirements with other major design codes.