Performance-Based Fire Safety Design in the UNITED KINGDOM · –Allows for alternative Fire Safety Engineering solutions –References other codes and standards for design of specific

Performance-Based Fire Safety

Design in the UNITED KINGDOM

Cecilia Abecassis Empis

1

TÆCRESEARCH • DEVELOPMENT • DESIGN • EDUCATION


OVERVIEW

2ORADOR

• Performance-Based Design

or Fire Safety Engineering

• Framework within Regulations

– AD B

– BS 7974

• Fire Safety Engineering designers

• Licensing Process & Legal Context

• Competence for Fire Safety Engineering Process


Goals

Functional

Objectives

Performance Requirements

Approved

Calculation

Method

Acceptable

Solution

Performance-Based

Alternative Solution

Prescriptive Standards:

Dictates how a building

should be designed/built

Performance-Based

Design Standards:

Stipulates how a building

should perform under a

number of different

conditions/scenarios

Under

development

Life Safety (& property/environmental protection)

Limit Fire Spread

Appropriate means of

detection and evacuation

Evacuation

times

Compartmentation

Guarantee structural

stability

Limit smoke toxicity

Smoke management

Structural protection

* Buchanan, A.H. (2002) Structural Design for Fire Safety, John Wiley & Sons, Ltd.,

U.K.

PERFORMANCE-BASED DESIGNaka FIRE SAFETY ENGINEERING


Prescriptive Standards:

Dictates how a building should be

designed/built

Performance-Based Design Standards:

Stipulates how a building should perform

under a number of different conditions

- Group of clauses often

based on empirical values

- No explicit evaluation of

level of safety

- In general appropriate for

generic buildings

- Analytical engineering

calculations

- Provides an explicit measure of

level of safety

- In general appropriate for

unique/singular buildings

* Buchanan, A.H. (2002) Structural Design for Fire Safety, John Wiley & Sons, Ltd.,

U.K.

PERFORMANCE-BASED DESIGN

Goals

Functional

Objectives


Approved

Calculation

Method

Acceptable

Solution

Performance-Based


aka FIRE SAFETY ENGINEERING


FRAMEWORK WITHIN REGULATIONS

• General Fire Safety requirements set out in

Approved Document B (AD B):

– Prescriptive standard

– Allows for alternative Fire Safety Engineering solutions

– References other codes and standards for design of

specific sections

• Alternative Fire Safety Engineering approach set out

in BS 7974:2001:

– Applications of fire safety engineering principles to the

design of buildings – Code of Practice

5

AD B & BS 7974



• Approved Document B (Fire

Safety), introduced in 2000

• Two volumes:

– Vol.1 Dwellinghouses

– Vol.2 All other building types

• Clearly states functional

objectives

• Initial guidelines emphasise

alternative fire safety engineering

solutions can be used

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AD B



• Functional Objectives (AD B):

– B1. To ensure satisfactory provision of means of giving and alarm of fire and a

satisfactory standard of means of escape for persons in the event of a fire in a

building

– B2. To ensure fire spread over the internal linings of buildings is inhibited.

– B3. To ensure the stability of buildings in the event of fire; to ensure that there

is a sufficient degree of separation within buildings and between adjoining

buildings; to provide automatic fire suppression where necessary; and to inhibit

the unseen spread of fire and smoke in concealed spaces in buildings.

– B4. To ensure external walls and roofs have adequate resistance to the

spread of fire over the external envelope, and that spread of fire from one

building to another is restricted.

– B5. To ensure satisfactory access for fire appliances to buildings and the

provision of facilities in buildings to assist firefighters in the saving of life of

people in and around buildings.

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Goals

Functional Objectives


Approved

Calculation

Method

Acceptable

Solution

Performance-Based


AD B



• AD B allows for Approved Calculation Methods

and Performance-based Alternative Solutions:

8

Goals

Functional Objectives


Approved

Calculation

Method

Acceptable

Solution

Performance-Based


AD B



• AD B suggests Fire

Safety Engineering may

be the only way of

achieving adequate level

of safety in large and

complex buildings

• Suggests FSE can be

used to solve single

aspects of design or

whole strategy

• Refers BS 7974:2001

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AD B



10

AD B for Fire Safety Engineering



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AD B for Fire Safety Engineering

• No more reference to PBD and

FSE in ADB

• Layout of the document makes

‘localised’ PBD very

straightforward

• Breakdown makes identifying

intent/objective of individual

clauses easy



• BS 7974 introduced in 2001

• In 8 parts:

– General guidance

– Parts for specific sections of fire safety

strategy

• BS are guidance and

recommendations – should not

be quoted as if it were

specification;

12

BS 7974



13

BS 7974



14

BS 7974



15

BS 7974

• The BS 7974 framework:



16

BS 7974

• Essential to understand the intent of the code

• BS 7974 starts with a Quantitative Design

Review (QDR):

– Consider intent of each relevant recommendation

– A particular provision may have more than one

objective

– Develop alternative design solution

– Iterate until demonstrate proposed solution at least

as effective and reliable at meeting intent as the

conventional prescriptive approach

– Design team can include members of the approvals

bodies

• QDR should start at conceptual project phase

and be iterated, as necessary, as project

develops to detailed design phase



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BS 7974

• QDR Procedure:

– Review Architectural designs

– Establish fire safety objectives

– Identify fire hazards and possible consequences

– Establish trial fire safety designs

– Identify acceptance criteria and methods of

analysis

– Establish fire scenarios for analysis

• Quantitative Analysis, either:

– Deterministic design procedures

– Probabilistic design procedures

• Assessment against criteria:

– Deterministic, probabilistic, or comparative



• BS 7974 also makes recommendations on:

– Sub-systems (Parts 1-7) and how parameters of

design may interact (inter-dependency)

– The outline of report contents

• Emphasises the report should draw clear distinction

between life safety, property protection and

environmental protection

• It is assumed in the preparation of this BS that “the

execution of its provisions is entrusted to appropriately

qualified and competent people”

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BS 7974


FSE DESIGNERS

• No specific qualification requirements currently exist in

the UK for FSE designers

• For individual products and components certification schemes exist

• Accreditation of Installers and Maintenance firms

– Provides confidence in appropriate standard of workmanship, as fire performance of a

product, component or structure is dependent upon satisfactory site installation and

maintenance

• Third party accreditation of product and installation

conformity provide extra confidence in adequacy of systems

installed

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Who is appropriately qualified and competent to practice

Fire Safety Engineering (PBD)?


LICENSING PROCESS & LEGAL CONTEXT

• Building Control Bodies to accept adequacy of FSE

solutions (and product/component certifications) as

evidence of compliance with the relevant standards

• Legal responsibility therefore lies with the approvals

authorities

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…but the question of competence remains!


COMPETENCE FOR FSE PROCESS

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• Competence required to evaluate whether alternative solutions

comply with intent of the code:

– Fire Dynamics

– Heat Transfer: radiation, convection & conduction

– Compartment Fire Modelling (zone models, empirical & analytical

correlations)

– Background to empirical tools so can identify limits of applicability

– Fluid Dynamics & turbulence (for adequate use of CFD tools)

– Structural behaviour under transient and elevated temperatures

– Understand theory behind standard testing methods and material

behaviour under exposure to fire and different forms of heat exposure

– Understand limits behind behavioural modelling, etc….

What competence is needed to practice and approve

Fire Safety Engineering (PBD)?



22

• Those who practice Fire Safety Engineering in the UK:

– Usually Engineers

– Historically: with university degree in Engineering, Physics or

Chemistry

– Nowadays: with university or Postgraduate degrees in Fire

Safety Engineering

• For system to work, the Approval Authorities need same or

higher level of qualifications

• Authorities need the same or higher level of competence as

Professional Fire Safety Engineers

• Currently authorities often rely on Third Party Reviews by




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• Authorities need same or higher level of qualifications and

competence as Professional Fire Safety Engineers

• Authorities often rely on Third Party Reviews by Professional Fire

Safety Engineers

• Authorities ultimately still assume legal responsibility!

• How to judge competence of Third Party Reviewers?

• Structural Engineering works on self-certification

• Chartered Structural Engineers sign-off on projects and take

responsibility, backed by their charter institutions

• Adequate National and International Chartering Bodies are

necessary to evaluate engineering competence of FSE engineers,

for an effective system


SUMMARY

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• UK Legislation allows for Performance-Based

Design or Fire Safety Engineering

• FSE designer must ensure proposed solutions

comply with the intent of the codes (functional

objectives)

– Whether Prescriptive solutions are applied

– Or an alternative Performance-Based Design

• Building Control Bodies (authorities) approve FSE

designs and are legally responsible

• Authorities often rely on Third Party Reviews by



Cecilia Abecassis Empis, PhD MEng

Director & Senior Engineer

TORERO, ABECASSIS EMPIS and COWLARD Ltd

E | [email protected] | W | www.taec.engineering

RESEARCH • DEVELOPMENT • DESIGN • EDUCATION

Documents

Performance-Based Fire Safety Design in the UNITED KINGDOM · –Allows for alternative Fire Safety Engineering solutions –References other codes and standards for design of specific