Abstract. Advanced simulations are becoming a common approach for dealing with complex fire safety problems. The use of specially developed software for fire and evacuation modelling allows fire safety problems to be solved in a way that was not possible just a few decades ago.
Performing advanced simulations requires a deep knowledge of both Fire Engineering and Fire Engineering Modelling. Engineers are often responsible for the life safety analysis, and are equipped with a number of tools to aid the design process. One challenge is to understand how to use such tools, but of equal and paramount importance is understanding their limitations, and thus when their use is not appropriate.
Nowadays advanced modelling forms a natural part of a Performance Based Design approach. Common areas of practice are Evacuation modelling and Fire & Smoke modelling and often a combination of both when assessing the fire safety performance of a building. Although both the means of escape for a building and a smoke control system could be designed following prescriptive requirements, many examples exist where a performance based approach is the only way forward and advanced computer models become an essential part of the Fire Safety Design.
Safe, robust, and practical solutions that account for human behaviour as well as advanced tools that predict the fire and smoke behaviour in a building are an essential component of any building design. Designers need to provide innovative designs whilst providing safe buildings.
In particular, the paper shows a series of case studies when advanced modelling were successfully utilized, these are:
The computer models used to perform the analyses were Pathfinder and Fire Dynamics Simulator. JVVA has used such models to evaluate, optimize and design singular buildings. The intention of this paper is to show how advanced modelling has been a vital part of the design process.
The increased use of performance-based design to develop fire safety solutions requires, for complex buildings, the use of advanced tools in order to get answers that would not have been possible using hand calculations and simplified models. Spaces can be particularly vast, evacuation paths particularly complicated and the architectural layout might impose restrictions in such a way that the prescriptive requirements cannot be fulfilled or, in some case, are just the wrong approach for a particular space and use. Within a complex performance-based fire safety project, advanced modelling covers an important part but only when it is well integrated into the overall design process. The graph below, from the SFPE Handbook, shows the Performance based design flowchart and in red where advanced modelling is situated within the overall process.
Each element of the flow chart are essential and responsible for the final outcome. An analysis undertaken through advanced modelling can be right or wrong depending on how those earlier elements were introduced in the overall analysis itself. Once the evaluation phase is reached in the performance base design process, it is time to get into the modelling exercise. Figure X, below, shows the process of determining the right model to be used in the analysis. The model can be a simple algebraic correlations that can be solved with a calculator, a zone models or lumped parameter models that represent a space as a small number of elements, to computational fluid dynamics or field models which approximate a space as a large number of discrete volumes.
Story of success exists where the use of performance-based design solutions has leaded to truly advanced solutions which have benefited the client and the building. Four examples have been selected and shown in this paper, outlining the role of the advanced modelling in the overall design process.
The first example is the largest and busiest airport in Spain. The overall objective of the project was to evaluate the current fire safety level for all existing terminals. The study was specifically orientated at fire risks, the main objective was to identify additional fire safety measures that could be incorporated into the building and also quantify how these measures impacted on the current fire safety level.
Specifically for this example, the largest terminal (T4) is shown. Due to the complexity and dimension of the building, advanced modelling was necessary. Both advanced evacuation analysis and Fire and Smoke modelling were performed for the terminal with the aim of evaluating the efficiency of the current evacuation routes together with the efficiency of the smoke control system, when available. For this analysis, Pathfinder 2015 was used for the evacuation modelling and FDS v.6.2.0 for the fire and smoke modelling. The first step in the analysis was to evaluate the existing configuration. The following image shows an example, commercial area in the airside departures level, during a simulated evacuation. As can be seen on the image a few large bottleneck areas were created using the current evaluation strategy for this level.
The analysis of the current configuration shown various conflictive points where people were stuck or simply the evacuation was not as fluid as it could have been. Minor changes have been introduced to the evacuation routes with almost no impact to the building with a substantial improvement of the building safety. By the increment of two corridors width together with the redirection of the part of the occupants toward the bridges instead of into a long corridors that was currently in use, the overall evacuation time was reduce by means of 30%.
In addition, there were several exits that were sub-utilized and did not really add value to the evacuation. By the introduction of a clearer wayfinding system (signage), omitting exits and creating additional exits (using existing non-used routes), there was a clear improvement in both evacuation time (reduced about 40 %) and in regards to the bottlenecks (which were heavily reduced as well). Together with the evacuation analysis, conditions for the occupants in case of fire have been assessed through fire and smoke modelling. The whole terminal has been modelled since it represented a single unique large compartment. The model was processed with FDS v.6.2.0, the domain was split into 30 different meshes assigned to 30 MPI processes, with a resolution varying from 0.10 m in the fire region up to 0.40 m in the regions far from the fire.