Performance objectives for non-structural elements

Abstract

The recent earthquakes in New Zealand have raised awareness of the seismic vulnerability of non-structural elements and the costly consequences when non-structural elements perform poorly. Impacts on business continuity due to the damage of non-structural elements has been identified as a major cost and disruption issue in recent earthquakes in New Zealand, as well as worldwide. Clearly improvements in performance of non-structural elements under earthquake loads will yield benefits to society. This paper explores the intended and expected performance objectives for non-structural elements. Possible historic differences in performance objective expectations for non-structural elements between building services engineers, fire engineers and structural engineers are discussed. Wider construction industry expectations are explored along with our experience of client and regulatory authority views. The paper discusses the application and interpretation of the New Zealand earthquake loadings Standard NZS1170.5:2004 for the design of non-structural elements including possible differences in interpretation between building services, structural and fire engineers leading to confusion around the expected performance of non-structural elements under different limit states. It is based on the experience of several of the authors as members of the Standards committee for NZS1170.5:2004. The paper concludes by discussing changes to NZS1170.5:2004 the authors have proposed as members of the NZS1170.5 Standards committee to clarify and address the identified issues. These changes clarify the classification of parts, requirements for consideration earthquake imposed deformations, parts supported on ledges, potential falling of parts, the combination of fire and earthquake loads, and the requirement for parts to be designed for both serviceability and ultimate limit states along with the effective introduction of a serviceability limit state for parts for occupational continuity.