How a performance-based approach to fire safety improves stadia design

An interview with Stephen Logan, Design Director, Buildings

1. Why should fire safety be so important in stadium design?

Often, the conversation between the lead architect and engineering team and the fire safety engineer is one of the last to be had. In my opinion it should be one of the first!

The reason for this is that, done well, fire safety engineering opens up so many design possibilities that the rest of the team may not have appreciated. Design teams so often constrain themselves by wrongly perceived building code compliance.

Fire safety engineering done poorly is passive and reactive, merely addressing problems that others bring. Fire safety engineering done well is seeking opportunity for better, safer design. Done well, fire safety can improve the overall design and amenity of the stadium.

2. How does fire safety engineering enhance safety?

You have to think about how the existing prescriptive codes have evolved. In a way, they arise as a result of ’codifying by catastrophe’. Historical adverse outcomes, such as loss of life in fire, are responded to (quite reasonably) by more onerous building regulations. But these regulations, built up over time, can become illogical for some types of buildings.

The English Green Guide (also known as The Guide to Safety at Sports Grounds) is a classic example of codifying by catastrophe as it was produced following the horrific Bradford and Hillsborough stadium disasters in the UK, in the 1980s.

Many building codes and regulations around the world initially evolved in the same way. Numerous modern building codes (including the Australian National Construction Code) recognise the limitations of a purely prescriptive approach and instead simply require a series of performance requirements be met.

A performance-based approach demonstrates fire safety.

This is where the expression ‘performance-based fire engineering’ emanates. As it would not be cost effective or sensible to adopt a different performance-based solution for every routine project and every fire safety system, there are also prescriptive clauses. In effect, this is a recipe book of measures that are ’deemed to satisfy’ the performance requirements.

The language of this is revealing. You can say that if you follow the prescriptive clauses, you are assuming that this gives you a safe building, because the codes are deemed to satisfy the performance codes. By comparison, a performance-based approach demonstrates fire safety.

Some people seem to think that adopting a performance-based approach is about cutting cost or getting away with things. In fact, it is about demonstrated, rather than assumed safety.

3. Are there other benefits of fire safety engineering?

Apart from proving that the building design is safe, fire safety engineering offers:

• Improved life safety
• Greater architectural flexibility
• Less waste
• Less complex systems to maintain
• Less cost

4. Why haven’t we always utilised fire engineering methods?

Fire engineering has only existed in any significant form since the 1980s. Part of the reason is that fire engineering is heavily reliant on computing power and software tools.

Another part of the reason is the gradual worldwide trend away from building approval by local government and towards more uniform, performance-based codes. This is a good thing because local authorities sometimes don’t have the capability to deal with large complex projects.

5. What are the big issues in stadium fire engineering?

The main issue is the number of people and their behaviour. The fire safety strategy in a stadium should be considered from a behavioural perspective. There are also other significant issues:

Architectural flexibility – Following prescriptive codes would limit fire compartment sizes, requiring the architect to put walls and doors where they might not otherwise be desirable. It can lead to requirements for very large fire escape stairs.

Protection of steel – Steel structures are common in stadium design and they are also often comprised of very large steel sections. So, it doesn’t make sense to clad them in fire spray, because they are never going to fail. They just can’t get hot enough in a fire.

Escape paths – Populations in stadiums are high. If escape paths are calculated in the normal way, the perimeter of the stadium can be dominated by escape stairs and concourse widths can become excessive. A better way is to simulate egress flows using computational modelling and optimise the escape paths.

A significant issue is thinking about the behaviour of the occupants and designing the fire safety systems from there.

6. How do people behave in a fire situation? Is panic a big problem?

To the contrary, panic is not usually a problem. In general, people don’t panic. In fact, in a few situations a bit of panic would have improved things – like in the Bradford Stadium fire when people remained in their seats waiting for the game to restart, when they should have been evacuating.

In a fire emergency, most people go through four behavioural steps before they even begin to evacuate:

1. Disbelief – Patrons don’t believe it is happening. If they hear an alarm, they will tend to assume it is a false alarm.
2. Commitment – Patrons typically finish what they are doing. If they are buying a snack, they will finish doing that before they investigate further. In the Kings Cross Underground fire in the 1980s people were observed stepping over hoses deployed from fire trucks to get to escalators to go underground. They were committed to getting their train home. In numerous tests in the retail environment, patrons observing actual smoke will take their goods to the check-out, rather than move to a fire escape.
3. Affiliation – Patrons assemble in friends/family groups, and won’t evacuate until then. This is a huge issue in stadiums. If a patron away from their seat is convinced that there is a fire emergency, they will not evacuate – they will return to their seats to re-unite with family members first.
4. Seek authority figures – Once they have formed their social and family groups, they will look for authority figures to tell them what to do. However, they must be perceived as having authority. A teenage usher employed on the day of the event may not be perceived as an authority figure. Where do people in a sports stadium look if they don’t know what is going on? The scoreboard!