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FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Fire Safety => Topic started by: Benzerari on February 01, 2009, 01:05:02 AM
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What is the difference between 'prescriptive-based codes' and 'performance based-design codes' in regards to fire safety standards?
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Is BS5839..., a ‘prescriptive based codes’, or ‘performance based design codes’, or a mixture of both?
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Prescriptive codes or requirements tell you what you should be doing - eg Smoke detectors must be possiitoned no more than 5m apart....
Performance based codes or requirements set a specific performance - eg The fire detection system should be designed so that it detects a fire within 30 seconds (for this you need standard methods of calculation which cannot be varied)
Functional based requirements set out the objectives - eg A suitable fire detection system should be provided...(you can go all the way to - the building should be reasonably safe if there is a fire)
BS 5839 is esentially a prescriptive standard. This kind of standard is used by specifiers and regulators as a kind of shorthand. Rather than describing what they want in infinate detail (which they probably arent qualified to do) they just call up a standard spec. There are sometimes functional nad perfermoance based elements to codes like this.
Most of the Building Regs requirements (in England and Wales) are functional.
A lot of people think that fire safety engineering design is performance based but it isn't (or c ertainly very rarely). FSE is usually used to show compliance with a functional requirement.
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Sorry wee brian for being so thick but your abbreviation FSE what does it mean.
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FSE - Fire safety engineering
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Prescriptive codes or requirements tell you what you should be doing - eg Smoke detectors must be possiitoned no more than 5m apart....
Performance based codes or requirements set a specific performance - eg The fire detection system should be designed so that it detects a fire within 30 seconds (for this you need standard methods of calculation which cannot be varied)
Functional based requirements set out the objectives - eg A suitable fire detection system should be provided...(you can go all the way to - the building should be reasonably safe if there is a fire)
BS 5839 is esentially a prescriptive standard. This kind of standard is used by specifiers and regulators as a kind of shorthand. Rather than describing what they want in infinate detail (which they probably arent qualified to do) they just call up a standard spec. There are sometimes functional nad perfermoance based elements to codes like this.
Most of the Building Regs requirements (in England and Wales) are functional.
A lot of people think that fire safety engineering design is performance based but it isn't (or c ertainly very rarely). FSE is usually used to show compliance with a functional requirement.
Thanks W. Brian, any more refinements guys :)
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A lot of people think that fire safety engineering design is performance based but it isn't (or certainly very rarely). FSE is usually used to show compliance with a functional requirement.
Fire safety engineering design uses engineering solutions such as CFD, PRA... approaches and it's all based on calculations, how that can not be performance based design W.Brian?
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Also, I have heard that amongst the developed world, the British on 1985, followed by New Zealand on 1992, then Australia on 1995 were the first to publish performance-based design codes.
What are the British performance-based design codes, if other than BS5839?
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AD B
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The regs in UK NZ and AU are not performance based, they are functional.
Fire safety engineering is usually carried out using comparative studies against the codes rather than to meet a particular performance.
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The regs in UK NZ and AU are not performance based, they are functional.
Fire safety engineering is usually carried out using comparative studies against the codes rather than to meet a particular performance.
W.Brian;
Your probably right but still, I couldn't get my head round in here, or may be I am confused, since I heard for the first time of the word 'functional codes'.
Do you mean functional is both 'prescriptive' and 'performance-based' combined together?
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In practice you could describe functional systems that way.
For England and Wales there are 5 functional requirements in the building regs relating to fire safety.
Approved Document B (AD B) is essentially a prescriptive code that provides an acceptable way of meeting those requirements.
However designers can adopt alternative approaches to compliance if they can satisfy the Building Control Body that their proposals are acceptable. This is usually done by demonstrating/arguing that the design offers a similar level of safety to the AD solution. You could call this a performance based approach but it isnt really a pure performance based design as performance is not specified in tangable terms.
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In practice you could describe functional systems that way.
For England and Wales there are 5 functional requirements in the building regs relating to fire safety.
Approved Document B (AD B) is essentially a prescriptive code that provides an acceptable way of meeting those requirements.
However designers can adopt alternative approaches to compliance if they can satisfy the Building Control Body that their proposals are acceptable. This is usually done by demonstrating/arguing that the design offers a similar level of safety to the AD solution. You could call this a performance based approach but it isnt really a pure performance based design as performance is not specified in tangable terms.
So no thing else in UK closer to performance-based code apart from AD B, as Colin stated previously?
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I think BS7974 might be close to what you are looking for.
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You've fallen into the trap Civvy. There's no performance specified in 7974 so it can't be a performance based code, now can it.
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Fair comment.
From the document: (From PD7974 part 0)
This conclusion is equally applicable to building design and BS 7974:2001 has been developed to provide an
objectives-based approach to fire safety in buildings.
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BS 7974:2001 provides a performance-based approach to design in which the specific fire hazards and their
potential consequences are identified and fire safety measures can be introduced, as necessary, to ensure
that the design objectives are met. It also enables the results of recent research into fire and human
response to be translated directly into the building design process.
The QDR process stated in BS7974 sets the performance requirements, so while minimal actual performance criteria is in the codes, (Certain criteria such as suitable limits for tenability are included though) it does point the designer towards setting their own.
This criteria will often be linked to the functional requirements of the building regs. If they go for a comparative study then I don't think they are truly looking at performance, but if they go for the ASET vs RSET thing properly then that is heading more towards performance. i.e. It takes people 15 minutes to evacuate, and we can maintain tenable conditions for 30 minutes. The 'performance' required is the safe evacuation of the building, thus complying with part B1.
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Fair comment.
From the document: (From PD7974 part 0)
This conclusion is equally applicable to building design and BS 7974:2001 has been developed to provide an
objectives-based approach to fire safety in buildings.
---
BS 7974:2001 provides a performance-based approach to design in which the specific fire hazards and their
potential consequences are identified and fire safety measures can be introduced, as necessary, to ensure
that the design objectives are met. It also enables the results of recent research into fire and human
response to be translated directly into the building design process.
The QDR process stated in BS7974 sets the performance requirements, so while minimal actual performance criteria is in the codes, (Certain criteria such as suitable limits for tenability are included though) it does point the designer towards setting their own.
This criteria will often be linked to the functional requirements of the building regs. If they go for a comparative study then I don't think they are truly looking at performance, but if they go for the ASET vs RSET thing properly then that is heading more towards performance. i.e. It takes people 15 minutes to evacuate, and we can maintain tenable conditions for 30 minutes. The 'performance' required is the safe evacuation of the building, thus complying with part B1.
Thanks Civvy for this input;
By the way how much cost BS7974 2001?
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It will be particularly expensive as it is a suite of documents. There is the BS7974, then there are the 8 PD's that accompany it. To use it properly you really need the whole suite, as they all interact
BS7974 = £138
PD7974-0 = £158
PD7974 part 1 = £180
Part 2 = £168
and so on to part 7...
Also, BS7974 and PD7974-0 are particularly similar.
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Thank you Guys all, for your inputs;
I forgot that some thing has been mentioned in the article of Belsham in fire risk management journal and has been brought up to the forum by Kurnal in some thread, about BS7974.
Thank you