## 3 Case Studies
### Objectives and Performance Requirements  
The first proposed design (Case 1--ABCB) is a 20-storey residential occupancy building with twelve units per floor. The performance solution provides a single fire stair for each floor while the DTS solution provides a double exit stair in compliance with the requirements from NCC. Both designs are taken from the FSVM Handbook and are shown in Figure 2. Table 1 summarizes the main characteristics and differences between the two solutions. When examining the floor plan of a single floor, space saving by using a single fire stair does not appear to be significant, however the space savings over twenty floors can be quite significant. Additionally, construction cost savings from not constructing the second stair compartment is also substantial. The comparison of the two designs shows that the performance requirement that is not met by the proposed design is the DP6 (Paths of Travel to Exits) requirement. The building is classified as a Class 2 building according to the NCC, Volume 1. Given the height of more than 25 m, the DTS design shall have at least two exits from each storey. The second element of non-compliance for the performance solution is the exit travel distance (D1.4) [21]. The DTS condition requires that the 'entrance doorway of any sole-occupancy unit must be not more than 6 m from an exit or from a point from which travel in different directions to two exits is available'. Moreover, the distance between alternative exits must be not less than 9 m and not more than 45 m.  
These DTS requirements are expected to be compensated by introducing other safety measures that are not contemplated in the DTS solution. The method used to compare the risk in the two buildings is the T-H-O-Risk method. The output from the application of the method to the two solutions will generate two risk values that will be compared to assess the level of safety of the performance solution. Using the FSVM, a selection of the design scenarios can be made based on the performance requirement that is violated (using Table 1.2 of the Handbook for FSVM [21] as a guide). Consequently, the design scenarios that need to be modelled are as follows: \begin{table}
\begin{tabular}{c c c} \hline \hline
**Building Characteristics** & **ABCB DTS** & **ABCB Performance** \\ \hline Occupants per floor & 36 & 36 \\ Number of floors & 20 & 20 \\ Floorplate area (m\({}^{2}\)) & 702 & 702 \\ Number of units per floor & 12 & 12 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Characteristics of Case #1- Australian Building Codes Board (ABCB) Deemed-to-Satisfy (DTS) and Performance solutions. Figure 2: Two solutions for Case #1 Australian Building Codes Board (ABCB) model residential building. * BE--Blocked Exit, a fire blocks the evacuation route; it is necessary to demonstrate through ASET/RSET and ERL analysis that the level of safety is at least equivalent to the DTS provisions. * CS--Concealed Space, a fire starts in a concealed space that can spread and harm several people in a room. The solution might include fire suppression or automatic detection. * SF--Smouldering Fire, a fire is smouldering close to a sleeping area. The solution may provide a detection and alarm system. * IS--Internal Surfaces, interior surfaces are exposed to a growing fire that potentially endangers occupants. * CF--Challenging Fire, the worst credible fire in an occupied space. * RC--Robustness Check, failure of a critical part of the fire safety system will not result in the design not meeting objectives of the NCC (modified ASET/RSET analysis to demonstrate that the remaining floors or fire compartments are robust). For each of the fire scenarios, a fire modelling simulation based on fast t-squared fire (\(\alpha\) = 0.0469) up to flashover will be performed to determine ASET based on tenability limits.