Types of alternative solution and analysis principles
Alternative solutions can take a number of different forms that can be simply classified depending on their level of complexity. This level of complexity depends on the extent the proposed design deviates from the Acceptable Solutions or Verification Methods.
Alternative solutions for fire design can be broadly categorised as one of the following:
- single minor departure from the Acceptable Solutions
- single major or multiple departures from the Acceptable Solutions
- departure from a Verification Method
- specific fire engineering design.
It is specifically noted that the clauses contained within the Acceptable Solutions and Verification Methods are not stand-alone. There are interdependencies across clauses in separate sections of those documents. When developing an alternative solution it is critical to identify any flow-on or secondary affected clauses and ensure these are also robustly addressed in the proposed solution.
For example, an alternative solution to C/AS6 4.13.7 (‘The total area of the intermediate foors within the firecell shall not exceed 35 m2’) to extend the permitted area of mezzanine must also include due consideration of clauses relating to the proposed:
- detection systems
- occupancy
- egress width
- floor fire rating
and appropriate justification must be provided.
The required consideration of all appropriate Acceptable Solution, Verification Method and Building Code clauses highlights the importance of early stakeholder involvement and a thorough FEB process.
Fire Engineering Brief has more information.
Expertise needed for alternative solutions for fire design
Fire engineering principles relate to the interaction between fire dynamics and human behaviour. An alternative solution proposal can require complex understanding of fire and smoke development and the behaviour and interaction of occupants. Protection of other property requires understanding of structural behaviour in fire, large fire development and radiant heat.
For these reasons even a seemingly simple alternative solution should be undertaken by a suitably qualified or experienced building professional.
Approaches and methods of analysis
There are many and varied approaches to the development of analysis to support an alternative solution. The key is to establish at an early stage of the project, ideally through the FEB process, the appropriate analysis approach or approaches.
International Fire Engineering Guidelines 2005 on the Australian Building Codes Board website provide guidance on approaches – these are:
- comparative or absolute approach
- qualitative or quantitative approach
- deterministic or probabilistic approach.