@article {bnh-6819, title = {Physics-based simulation of firebrand and heat flux on structures in the context of AS3959}, number = {560}, year = {2020}, month = {04/2020}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

Firebrand is known as one of the most dangerous airborne components of wildfires having the potential to ignite structures in Wildland-Urban Interface (WUI). Quantifying the firebrand and heat flux on structures is essential to determine the wildfire risks and prepare strategic plans to mitigate the hazard. We endeavor to use a physics-based model, Fire Dynamic Simulator (FDS) to map firebrand and heat flux to determine the vulnerability of structures in WUI. In this study, we have validated FDS{\textquoteright} tree burning and firebrand transporting sub-models against the experiment conducted in no wind condition at the National Institute of Standards and Technology (NIST). The experimental data of firebands were processed to use as inputs in the numerical simulation and the grid convergence was appraised in terms of mass loss rate (MLR). The intial velocity and direction of firebrands, the number of generations were determined as model inputs by a reverse analysis through comparing firebrand distribution with the experiment. As the FDS{\textquoteright} sub-models were validated, we attempted to quantify the heat flux and firebrand risk on a structure at three different driving wind velocities. Increasing wind speed showed more firebrands transported towards the structure but none of them landed on the house because of the low height of the tree and insufficiency of fire-induced buoyancy to lift them enough to carry a longer distance by the wind field. Similarly, heat flux computed on the structure is well below Australian building standard AS3959{\textquoteright}s bushfire attack level (BAL). it is due to the low heat release by single tree burning instead of a 100m wide fire line assumed in the standard. In future study, simulations will be conducted with a cluster of taller trees (100m wide) to quantify the heat flux and firebrand hazard on structures to apprise AS3959.

}, keywords = {firebrand, heat flux, physics simulation, structures}, issn = {560}, author = {Amila Wickramasinghe and Nazmul Khan and Khalid Moinuddin} } @conference {bnh-6407, title = {Modelling the vulnerability of a high-set house roof structure to windstorms using VAWS }, booktitle = {Bushfire and Natural Hazards CRC Research Day AFAC19}, year = {2019}, month = {12/2019}, address = {Melbourne}, abstract = {

Modelling the vulnerability of houses in windstorms is important for insurance pricing, policy-making, and emergency management. Vulnerability models for Australian house types have been developed since the 1970s and have ranged from empirical models to more advanced reliability based structural engineering models, which provide estimates of damage for a range of wind speeds of interest. This paper describes recent developments in the engineering based vulnerability modelling software: {\textquoteleft}Vulnerability and Adaption to Wind Simulation{\textquoteright} (VAWS), which uses probability based reliability analysis and structural engineering for the loading and response coupled with an extensive test database and field damage assessments to calculate the damage experienced by selected Australian house types. A case study is presented to demonstrate the program{\textquoteright}s ability to model progressive failures, internal pressurization and debris impact.

}, keywords = {debris, simulation, structures, VAWs, Vulnerability, wind}, url = {https://knowledge.aidr.org.au/resources/australian-journal-of-emergency-management-monograph-series/}, author = {Korah Parackal and Martin Wehner and Hyeuk Ryu and John Ginger and Daniel Smith and David Henderson and Mark Edwards} }