Extended travel distance in residential apartment building - A comparative risk model

Abstract: Prescriptive building codes have been used for many years and created a common sense regarding what an adequate fire safety design and an acceptable level of risk is. Introducing performance based building codes brought architectural flexibility, more bespoke design, and cost-benefit analysis into fire safety design previously not possible in a number of different building types. Alternative Solutions are now common place in almost every residential apartment building in Australia and often includes a number of typical non-compliances such as extended travel distances between apartments and exits. However, it is not that easy to accurately evaluate the level of safety provided by a fire safety design in a residential building. The reasons for that are many such as the complexity of the system (both active and passive systems), the different aspects affected during a fire (all sub-systems in the IFEG) but also the harsh commercial conditions during a residential building project. The objective of this thesis was therefore to investigate if (or to what degree) the inclusions of passive and active systems compensate for the increased risk due to the extended travel distance for any given (non-compliant) building solution. This was done through the development of a comparative risk model for residential buildings with a focus on the impact of extended travel distance on occupant life safety. The developed risk model indicates that the main contribution to the risk to occupants when travel distances are increased in residential buildings can be derived from the increased number of apartments. By adding more apartments connected to a corridor, the probability of a fire to occur on that level, as well as the consequence for all scenarios when smoke leaks into the corridor are increased. Therefore the relative risk nearly increases as the square of the number of apartments increase. The difference in travel time due to the extended travel distance was shown to not have any measurable impact on the risk level for corridor lengths between 7 m and 25 m in length.