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The use of discrete damping devices in New Zealand buildings is increasing as designers seek to limit damage to both architectural and structural building elements in moderate earthquakes. The overall damping of the structure becomes a combination of inherent material damping, hysteretic damping from yielding of building elements at specific locations and damping from discrete devices. For over 60 years, engineers have used simplified analysis procedures (e.g., modal response spectrum analysis) to predict building response under seismic actions. The design of structures incorporating viscous dampers requires a paradigm shift in approach as the force each damper resists is a function of the relative velocity between its ends. Popular pseudo-static design methodologies promote the use of a viscous strut in the analysis model to represent them. However, it is incorrect to use elastic, mode-based analysis for a structure incorporating damping devices and relying on significant inelastic behaviour. This paper elucidates the complex mechanics of damper-structure interaction by reviewing some of the established classical, modal-based, simplified analysis techniques used in seismic design. A series of numerical investigations demonstrate how these techniques are usually invalid for structures that incorporate viscous dampers because they violate the laws of physics. The reason why mode-based techniques are invalid is explored with reference to the imaginary components of the natural modes of vibration and the effect on them of significant inelasticity within the structure. The dynamic characteristics of viscous dampers challenge conventional design approaches such as displacement-based design. This paper establishes that nonlinear time-history analysis is the only meaningful way of predicting the dynamic response of a structure incorporating viscous dampers when significant inelastic behaviour of the structure is expected. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]