Calculating how long a building can be evacuated in an emergency is an important consideration for human life during building design. Analytical methods are available to calculate in fire codes and standards (SFPE, NFPA, BS, DIN, etc.). These codes and standarts set minimum requirements for the safe design of multi-storey buildings. However, additional safety measures are often required to reduce the risks associated with the complexity of such buildings and potential difficulties in fire fighting and rescue operations. Also, recent events such as the evacuation of the World Trade Center have raised awareness. Inquiries about the adequacy of existing emergency procedures for buildings have increased. In order to evacuate multi-storey buildings, inquiries were made as to which output components (eg stairs, elevators, shelters, sky bridges, etc.) were most appropriate. What emergency procedures should be used to improve evacuation efficiency? These questions do not have simple answers and usually depend on the characteristics of the building under investigation.
In the analysis studies, modeling of each room, zoning, defining the number of users and their many features (shoulder width, walking speeds, behavior types) is calculated by simulating how many minutes the place can be evacuated. The consistency of performance-based calculations has been reported in the literature with many case studies conducted for validation and verification so far. With this approach, it is quite possible that the architectural design can detect the critical crowd zones that may occur with quick and simple changes, and see the improvement of the results by making simple arrangements in the corridors that will cause clogging.
Evacuation analysis: performance-based egress time calculation
Short answer: Evacuation analysis calculates how long a building can be evacuated in an emergency through a simulation that models each room/zone; it delivers a performance-based assessment within the framework of standards such as SFPE, NFPA, BS and DIN.
The consistency of performance-based calculations has been established in the literature through many validation and verification case studies to date; this approach lets the architectural design catch critical crowding zones early through quick, simple changes and correct corridor arrangements that would otherwise cause clogging, before construction.
When is this needed?
- When the building or its use is more complex than the code calculation covers — for example when several exit components (stairs, elevators, refuge areas, sky bridges) need to be assessed together
- For large mixed-use volumes such as atriums, malls or stadiums
- When an elevator-based evacuation strategy (vertical circulation) needs evaluating
- When approval for a performance-based design is sought for a non-code solution
Input parameters
| Parameter | What it represents |
|---|---|
| Room/zone definition | Defining the modelled areas and boundaries of the building |
| Occupant count and distribution | The number and location of people present at the moment of evacuation |
| Shoulder width, walking speed, behaviour type | Physical and behavioural characteristics of occupants; values are scenario-based per project |
| Exit components (stairs, elevators, refuge areas, etc.) | The capacity of the available evacuation routes |
Worked case: Orbi Group — Batumi
The high-rise mixed-use projects of Orbi Group — Georgia’s leading developer — in Batumi, with their shopping-centre, hotel and residential components, carry intense pedestrian use. Combining a high-density mall with multi-storey towers calls for emergency evacuation scenarios and elevator (vertical-circulation) traffic to be optimised through advanced simulation. Alkazar carried out human-evacuation and daily pedestrian-traffic analyses for these projects — an integrated safety and comfort assessment, from peak-hour pedestrian flow to emergency egress times.
Process and deliverables
| Steps | Deliverables |
|---|---|
| Building the room/zone model → defining occupant counts and behaviour parameters → evacuation simulation → identifying congestion/bottleneck zones → design and/or elevator-strategy recommendations | Scenario-based evacuation-time results, congestion maps, comparison of corridor/exit arrangements |
Reference project
- Orbi Group — Batumi: Human-Evacuation and Pedestrian-Traffic Analysis; Emergency Evacuation Scenarios; Elevator (Vertical-Circulation) Optimisation.
As on the Orbi Batumi project, evacuation analysis is usually handled within the same study as daily pedestrian-traffic assessment: normal peak-hour flow and emergency evacuation behaviour are run on the same model, as different scenarios.
Frequently asked questions
- How is evacuation time calculated?
- By modelling each room/zone, defining zoning and the number of occupants together with their characteristics — shoulder width, walking speed, behaviour type — a simulation calculates how many minutes it takes to evacuate the space.
- How does it differ from a code-based calculation?
- Code calculations set minimum requirements for the safe design of multi-storey buildings; performance-based simulation instead shows, from the building’s own geometry, occupant distribution and behaviour assumptions, how many minutes evacuation actually takes and where critical crowding zones occur.
- For which buildings is it recommended?
- For buildings whose complexity goes beyond the code, for large mixed-use volumes such as atriums, malls or stadiums, when an elevator-based evacuation strategy (vertical circulation) needs evaluating, and when approval for a performance-based design is sought.
- Is it combined with smoke/fire analysis?
- It can be combined where needed; criteria such as smoke movement and visibility fall under our Fire Physics and Smoke Control page.
- How is the reliability of the results validated?
- The consistency of this type of performance-based evacuation calculation has been established in the literature through numerous validation and verification case studies to date; simulation results can therefore be read not as a mere estimate but as a complement to the code calculation.
Related content
- Fire Physics and Smoke Control: Sibling service covering smoke movement and visibility analyses.
- Pedestrian-Level Wind Comfort: Related service for daily pedestrian traffic and outdoor usage.
