Abstract
Post-disaster reconnaissance reports frequently list non-structural components (NSCs) as a major source of financial loss in earthquakes. Moreover, minimizing their damage is also of vital significance to the uninterrupted functionality of a building. For efficient decision making, it is important to be able to estimate the cost and downtime associated with the repair of the damage likely to be caused at different hazard levels used in seismic design. Generalized loss functions for two important NSCs commonly used in New Zealand, namely suspended ceilings and drywall partitions are developed in this study. The methodology to develop the loss functions, in the form of engineering demand parameter vs. expected loss due to the considered components, is based on the existing framework for the storey level loss estimation. Nevertheless, exhaustive construction/field data are employed to make these loss functions more generic. In order to estimate financial losses resulting from the failure of suspended ceilings, generalized ceiling fragility functions are developed and combined with the cost functions, which give the loss associated with typical ceilings at various peak acceleration demands. Similarly, probabilities of different damage states in drywall partitions are combined with their associated repair/replacement costs to find the cumulative distribution of the expected loss due to partitions at various drift levels, which is then normalized in terms of the total building cost. Efficiencies of the developed loss functions are investigated through detailed loss assessment of case study reinforced concrete (RC) buildings. It is observed that the difference between the expected losses for ceilings, predicted by the developed generic loss function, and the losses obtained from the detailed loss estimation method is within 5%. Similarly, the developed generic loss function for partitions is able to estimate the partition losses within 2% of that from the detailed loss assessment. The results confirm the accuracy of the proposed generic seismic loss functions.
Highlights
Non-structural components (NSCs) make up a considerable proportion of the total building cost [1], often outweighing the cost of structural components in most building uses
The existing methodologies for floor level loss functions are extended in combination with component distributions to develop generalized functions for engineering demand parameter (EDP) vs. expected loss per square metre of floor area
Using the drawings of a 725 rooms from 29 different reinforced concrete (RC) office buildings in Christchurch Central Business District (CBD), a large data set of suspended ceilings and drywall partition sizes was collected
Summary
Non-structural components (NSCs) make up a considerable proportion of the total building cost [1], often outweighing the cost of structural components in most building uses. Even at small to moderate levels of ground shaking, where no noticeable structural damage occurs, damage to non-structural components (such as acoustic ceilings) and services can cause a substantial downtime resulting in a significant loss of income. Studies have shown that damage to non-structural components such as drywall partitions and acoustic ceilings (as well as generic components) comprise a significant proportion of the total loss in moderate earthquakes where no structural collapse occurs, and loss due to structural damage contributes little to the total loss [3]. The weeks-long closure of the modern BNZ building in Wellington, New Zealand, primarily due to ceiling damage during the Mw 6.5 Seddon earthquake on 16 August 2013 is a recent example. Recent earthquakes in New Zealand have directed the attention of engineers, policy makers and insurance companies toward NSCs and their significant contribution to the overall financial loss caused by such disasters, and significant progress has been made lately in understanding and improving seismic performance of NSCs [4]
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