The performance-based fire design process might only represent a portion of a typical project endeavor. Before commencing the PBFD effort, the purpose of the analysis must be established. This is done through various conversations with key project stakeholders, such as the architect, engineers, builder, building owner, and fire/building code officials.
Once the intent of the evaluation is well understood, the next step is establishing and documenting assumptions and justifications for the fire and egress modeling performance criteria. This includes information regarding proposed design fire scenarios, tenability criteria, occupant characteristics, parameters for sensitivity evaluation and other technical assumptions that influence the analysis. All of this information is documented within a Design Brief and formally presented to the authority having jurisdiction (AHJ) for review and preliminary approval.
Once the technical assumptions presented within the Design Brief are accepted by the AHJ, the fire and egress modeling process can begin. Fire and egress models are separate, standalone models developed in different software that can be leveraged independently, depending on the project scope. Often, however, they are overlayed for more meaningful results.
Generally speaking, the process for building each model is similar. First, the building geometry must be created within each modeling software. Next, various technical parameters must be specified within each software (this aligns with the justified assumptions within the Design Brief). This initial process is known as the model build and can take quite a bit of effort, ranging from 20 hours up to hundreds of hours for both the fire and egress models. This largely depends on the complexity and size of the building.
Once the modes are built, the next step involves an iterative process of running various simulations and making adjustments until the model shows that design objectives are satisfied. Simulation time can range from a couple of hours to a couple of weeks, depending on many factors. The most influential factors in simulation time include the overall mesh count and computer performance. This phase of the modeling often requires coordination with project stakeholders and can take a few days for everyone to get on the same page.
After baseline conditions are satisfied, a sensitivity analysis is performed. This is where the baseline results are tested against a wide range of environmental factors to ensure that the proposed solution is robust. Finally, the results are documented within a Final Report for AHJ approval. All-in, fire and egress modeling could take a few weeks or a few months, depending on many different factors.
