Evaluation of fragility functions with potential relevance for use in New Zealand

Abstract

One barrier to adopting seismic loss estimation frameworks in New Zealand engineering practice is the lack of relevant fragility functions which provide probabilities of exceeding certain levels of damage (e.g. cracking of gypsum wallboards) for a given demand (e.g. interstorey drifts). This study seeks to address this need for four different building components; interior full-height steel-framed plasterboard partition walls, unbraced suspended ceilings, precast concrete cladding, and steel beam-column joints with extended bolted end-plate connections. Fragility functions were sourced from literature, and their potential for use in New Zealand is evaluated considering similarities in component detailing with local practices. Modifications to a number of fragility functions, including generalizations for easier adoption in practice, are proposed. A loss estimation case study of a 4-storey steel moment-resisting frame is performed to investigate the significance of fragility function selection. It is shown that the definition of damage states can have a noticeable influence on the assessment of incurred repair cost of individual building components. This indicates that fragility functions should be carefully selected, particularly if the performance evaluation of each individual component is of utmost importance. However, the observed difference in expected annual repair cost of the entire building was small, indicating that in cases where fragility functions are not readily applicable for use in New Zealand, other fragility functions may be used as placeholders without drastically altering the outcome of loss analysis for the entire building.