Fire Engineering – Introduction

Prof. Y C WangRoom C2, Pariser Building

Tel: 0161 3068968Email: yong.wang@manchester.ac.uk

Importance of Fire Safety• Fire loss is about 1% GDP. The indirect loss can be more than the direct loss.• Fire kills about 600 people per year in the UK

• Fire safety is one of the two safety requirements for buildings, along with structural safety.

• Building design, construction and maintenance have to satisfy the requirements of Building Regulations (BR) Part B.

• In order for a building to obtain insurance, they also have to satisfy the requirements of the Insurance industry.

• The BR and insurance industry requirements cover similar issues, with the insurance industry requirements more stringent.

• Fire Engineering is an Engineering Council registered profession with specialist Chartered Fire Engineers. Good Fire Engineers are in high demand.

• A number of high profile fire accidents have raised the fire engineering more prominent.

• They reveal some inadequacies of the existing (prescriptive, ticking box) methods of dealing with fire safety.

• Recent research findings demonstrate flexibility and benefits of a “performance-based” approach.

Importance of an “Engineering” approach

What are the issues of fire safety and how to tackle them?

To control, contain and put out fire so that the affected people can evacuate to safety.

To minimise loss of property and business.

Anatomy of fire safety

requirements – small fire

• Fires usually start being small. During this stage, evacuation is reasonably unimpeded. Building design and construction should allow fast detection of fire, quick evacuation of people (B1, means of escape and warning).

• It is important that the speed of fire spread is controlled. Sprinklers are effective in controlling fires.

• Fire spread can also be controlled through using surface materials (lining) that are non-combustible or have limited combustibility (B2: internal fire spread, lining).

• During this stage, it is also relatively easy to fight the fire (B5).

Anatomy of fire safety requirements – large fire but contained within the initial

fire compartment• When the fire has grown and has

reached the flashover stage, the entire compartment of fire origin is involved in fire. Evacuation from the compartment is difficult due to high temperatures and concentrations of smoke and toxic gases.

• It is important that the fire does not spread beyond the compartment (containment), through the provision of fire resistant compartments (B3, internal fire spread, structures).

• Fire fighting (B5) continues to control fire spread and to put out the fire.

Anatomy of fire safety

requirements – external

• If the fire spreads externally, it is important that the neighbouring buildings are not affected (B4: external fire spread). This is done through controlling fire spread externally on the surface & sufficient separation distance between the buildings so that the radiation from the building in fire does not ignite the surface materials on the neighbouring building.

How to do Fire Safety Design• Probabilistic assessment: fire is a “random” event so a risk based approach is the most

appropriate. This approach is extremely complex and difficult to apply. There is also a lack of sufficiently robust statistical data. This method is usually used in simple building layouts (e.g. railway stations) and qualitative analysis.

• Deterministic assessment: although it does not adequately address the interaction of different sub-systems, this method is simple to perform and used in most cases.

• The traditional approach is prescriptive, telling what to do without stating the objectives. It is simple to do, but may not be flexible and may be costly. For example, the prescriptive approach specifies the travel distance in buildings, but the travel distance makes up only part of the evacuation design. Exposure through coursework.

• The performance-based, fire engineering approach has been developed to address the issues of lack of flexibility and high cost of the prescriptive approach. This requires thorough understanding of the fire safety requirements and competent applications of engineering methods. For example, the evacuation analysis is time based and it is important that the appropriate untenability condition is chosen and that there is high confidence in the calculation methodology of various terms of time. Main focus of course.

Probabilistic Risk Assessment

Example of Prescriptive Method

FE Approach: time based

The aim of applying a performance-based, fire

engineering approach is to enable elegant, flexible

and cost-effective buildings without

compromising on safety.

Learning outcomes of this course

• Learning outcomes:- To appreciate the application of fire engineering methods in fire safety design of

buildings;- to be able to carry out quantitative assessment of fire resistance of structures,

including fire behaviour, heat transfer and structural behaviour at elevated temperatures.

• Topics to be covered:- Small fire: some understanding of fire (plume) behaviour, fire detection, smoke

control, evacuation.- Large fire within fire compartment: main emphasis of this course, structural fire

safety.- Fire spread out of compartment: control of progressive collapse.

Syllabus & Schedule• Week 1: introduction to course & to heat transfer• Weeks 1-3: heat transfer• Week 4: Post-flashover fire behaviour• Weeks 5-10: structural behaviour and fire resistance design• Weeks 8&9 (Fridays): visit GMFRS• Week 11: introduction to pre-flashover fire dynamics &

applications to means of escape• Week 12: Invited industrial fire engineering presentation, revision

- Weekly arrangement: 2 hours formal lecture + 1 hour guided problem solving.

Assessment & Feedback• Assessment:• Exam (closed book, 3 hrs, 70%)• Coursework: (2 pieces, 30%)(1) Assessment of existing building to ADB: 10%, work in groups of four.Submission: Friday, 1 March 2013(2) Fire resistance design: 20%, to be issued in week 5, work in groups of two.Submission: Week 10

• Feedback• Information on Blackboard• Email to class via Blackboard • Email best way to get prompt feedback• Feedback: tutorial exercises/specific comments on individual coursework

reports + collective feedback/face to face meetings/emails

Reading Lists

1. An introduction to fire dynamics, 2nd edition, D. Drysdale, Wiley,ISBN0471972908, 1999

2. Enclosure fire dynamics, B. Karlsson and J G Quintiere, CRC Press, ISBN 0849313997, 2000

3. Steel and composite structures, behaviour and design for fire safety, Y.C.Wang, Spon Press, ISBN 0415244366, 2002

4. Structural design for fire safety, A H Buchanan, Wiley, ISBN 04718899335. Heat transfer, J P Holman, McGraw Hill, ISBN 0-07-240655-0, 20026. Various British and European standards (BS EN 1991-1-2, 1992-1-2, 1993-1-2,

1994-1-2, BS 5950 Part 8, BS 7974 & PDs, BS 9999) – Online database available through Library Web

7. Various documents from University Library electronic database “Construction Information Services”

8. YCW notes

Change of lecture time:1-2 pm Monday 3rd February

changed to 3-4 pm Tuesday 4th February, Renold E7