Modelling the effectiveness of retrofit to legacy houses requires a quantitative estimate of the houses’ vulnerability to severe wind and how the vulnerability is affected by mitigation work. Historical approaches to estimating vulnerability through either heuristic or empirical methods do not quantitatively capture the change in vulnerability afforded by mitigation. To address this information gap the Bushfire and Natural Hazards CRC project “Improving the Resilience of Existing Housing to Severe Wind Events” has augmented a software tool which models damage from wind loads and associated repair cost. In this paper the development process is described including the establishment of a suite of test cases to assess the effectiveness of the software. An example of the validation work is presented along with the augmentation of the software from the previous version. Finally, use of the software in assessing the incremental effectiveness of a range of mitigation strategies in economic terms is described. Abstract submitted to/presented at the19th Australasian Wind Engineering Society Workshop.

Modelling of the risk posed by the impacts of extreme weather events requires knowledge of the vulnerability, or performance, of building assets. Furthermore, to assess the benefits of mitigation an ability to quantitatively model the change in vulnerability associated with mitigation actions is required. In Australia past efforts at establishing vulnerability relationships between building damage and severe wind have centred on empirical techniques, using data from damage surveys or insurance losses, and heuristic techniques. Neither of these methods permits the change in vulnerability afforded by mitigation work to be quantitatively modelled. The Bushfire and Natural Hazards CRC project “Improving the Resilience of Existing Housing to Severe Wind Events” is developing a software tool, Vulnerability and Adaption to Wind Simulation (VAWS), to provide a quantitative vulnerability model for Australian house types. It is based on the premise that overall building damage is strongly related to the failure of key connections. The software uses a Monte Carlo approach whereby numerous realisations of a single generic house type are subjected to an increasing gust wind speed and the loss at each wind speed is calculated. Each realisation of the house varies from others as many key building parameters, such as connection strength, are sampled from probability distributions. For each instance, at each wind speed, the number and type of failed connections are related to damage states and extents of damage which permits the repair cost to be calculated. The repair cost is adjusted for the repair of debris impact damage and water ingress damage. The modelling of mitigation is easily accomplished by rerunning a house modelled with the probability distribution of an upgraded connection’s strength substituted. The software tool provides quantitative measures of reduced vulnerability that can be used in assessing the incremental effectiveness of a range of mitigation strategies in economic terms. Abstract submitted to/presented at AMOS-ICSHMO 2018 (https://www.ametsoc.org/index.cfm/ams/meetings-events/ams-meetings/amos-icshmo-2018/)