The LWF Blog

Fire Safety Engineering for Design – Evacuation Modelling – Part 127

April 11, 2023 10:36 am

LWF’s Fire Safety Engineering blog series is written for Architects, building designers and others in the construction industry to highlight and promote discussion on all topics around fire engineering. In part 126, LWF looked at how the exit capacity of a stairway can be calculated. In part 127, we discuss evacuation simulation models.

The use of computational evacuation modelling allows those people working in the field to assess the response and movement of people in emergency situations, as well as illustrating the flow of people and crowd movement and allowing assessment.

There are many different models available, all of which have different methods, capabilities and outputs. The common elements tend to be as follows:

  • A representation of the building’s layout
  • Occupants’ physical characteristics including size, walking speed etc.
  • Occupant behaviour, e.g. exit selection and response time
  • Occupant dynamics, e.g. occupant movements and interactions

Often the output includes a visual model of the movement of occupants within the building spaces. Time histories for such variables as occupant density, walking speed, door flow rates, door usage etc. are usually available. Some modelling software is able to incorporate the effects of fire and smoke on the occupants using data from computational fluid dynamics software.

As there are currently no standards pertaining to the assessments undertaken by the modelling software, each model is only able to represent the developer’s validation and verification of human behaviour. It is therefore imperative that the approach taken by the developer is clearly stated, along with any limitations of application.

The user must also make every effort to understand and address the limitations and to ensure their chosen model is suitable for purpose. Where possible, the computational evacuation model should be calibrated to most accurately reflect the building in question (particularly where the building is existing) and the people movement data gathered when on site.

Each system will no doubt also contain various user-adjustable parameters and the default option for each should not be assumed to be recommended or ‘standard’. Indeed, the use of settings which are not adjusted to suit the scenario in question can result in a simulation which does not reflect what may transpire in a space. Careful consideration should therefore be given to the parameters chosen for any situation.

Computational evacuation modelling tools can be a most effective and helpful tool when used properly and the visual outputs can allow design improvements which may not otherwise have been obvious.

In part 128 of LWF’s series on fire engineering, we will look at information and wayfinding systems. In the meantime, if you have any questions about this blog, or wish to discuss your own project with one of our fire engineers, please contact us.

Lawrence Webster Forrest has been working with their clients since 1986 to produce innovative and exciting building projects. If you would like further information on how LWF and fire strategies could assist you, please contact the LWF office on 0800 410 1130.

While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.

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