Sahani Hendawitharana

Early evacuation during bushfires remains the safest strategy; however, in many realistic scenarios, timely evacuation is challenging, making safe sheltering a last-resort option to reduce risk compared to late evacuation attempts. However, most Australian homes in bushfire-prone areas are neither designed nor retrofitted to provide adequate protection against extreme bushfires, raising safety concerns. This study addresses this gap by investigating the concept of retrofitting a part of the residential buildings as attached safe rooms for sheltering and protection of valuables, providing a potential last-resort solution for bushfire-prone communities. Numerical simulations were conducted using the Fire Dynamics Simulator to assess heat transfer and internal temperature conditions in a representative residential building under bushfire exposure conditions. The study investigated the impact of the placement of the safe room relative to the fire front direction, failure of vulnerable building components, and the effectiveness of steel shutters in response to internal temperatures. The results showed that the strategic placement of safe rooms inside the building, along with adequate protective measures for windows, can substantially reduce internal temperatures. The findings emphasised the importance of maintaining the integrity of openings and the external building envelope, demonstrating the potential of retrofitted attached safe rooms as a last-resort solution for existing residential buildings in bushfire-prone areas where the entire building was not constructed to withstand bushfire conditions.

Sheltering in place is identified as an accepted behaviour during disasters while safe rooms are purpose-built buildings used for sheltering or storage of valuables under these circumstances. However, ensuring the integrity of safe rooms in bushfires is complex and challenging due to many factors. This study aims to advance the understanding of the bushfire fire heat transfer in steel framed bushfire safe rooms using a numerical modelling approach. Both small-scale models of individual external walls and full-scale models of safe rooms were developed and validated using the results of an experimental study of a full-scale safe room. Then the study was extended to address the identified challenges in the design of safe rooms influenced by the factors such as, the fire exposed area, internal compartment arrangement, location of the safe room in the bushfire-prone areas, and the external environmental temperatures during summer on the tenability requirements. The results of this study provide considerable details of the performance of above-ground bushfire safe rooms detached from the associated dwelling under realistic fire conditions. They showed that the integrity of the doors is very important and that having multiple internal compartments is favourable for the bushfire performance of safe rooms. This study shows that safe rooms can be constructed using available building materials to satisfy the bushfire heat transfer requirements and provides conditions for their usage. Furthermore, the modelling methods emphasise their applicability to evaluate safe rooms and modular buildings in bushfire and building fire related scenarios.

This research investigated the heat transfer in safe rooms exposed to bushfires and their bushfire resistance using full-scale laboratory and out-door experimental studies of external wall systems and a safe room, and associated advanced numerical studies. It has advanced the knowledge and understanding of the heat transfer and the performance of the critical external building envelope and the safe rooms with different configurations exposed to bushfire flame conditions. Suitable solutions and methodologies have been proposed, addressing various complexities and challenges, which can be used in any bushfire-prone country like Australia. This will improve life safety and community resilience during bushfires.