Structural Design for Fire Safety E-Book

Andrew H. Buchanan

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch
• Veröffentlichungsjahr: 2016

Seitenzahl: 725

Beschreibung

Structural Design for Fire Safety, 2nd edition Andrew H. Buchanan, University of Canterbury, New Zealand Anthony K. Abu, University of Canterbury, New Zealand A practical and informative guide to structural fire engineering This book presents a comprehensive overview of structural fire engineering. An update on the first edition, the book describes new developments in the past ten years, including advanced calculation methods and computer programs. Further additions include: calculation methods for membrane action in floor slabs exposed to fires; a chapter on composite steel-concrete construction; and case studies of structural collapses. The book begins with an introduction to fire safety in buildings, from fire growth and development to the devastating effects of severe fires on large building structures. Methods of calculating fire severity and fire resistance are then described in detail, together with both simple and advanced methods for assessing and designing for structural fire safety in buildings constructed from structural steel, reinforced concrete, or structural timber. Structural Design for Fire Safety, 2nd edition bridges the information gap between fire safety engineers, structural engineers and building officials, and it will be useful for many others including architects, code writers, building designers, and firefighters. Key features: * Updated references to current research, as well as new end-of-chapter questions and worked examples. *Authors experienced in teaching, researching, and applying structural fire engineering in real buildings. * A focus on basic principles rather than specific building code requirements, for an international audience. An essential guide for structural engineers who wish to improve their understanding of buildings exposed to severe fires and an ideal textbook for introductory or advanced courses in structural fire engineering.

Leseprobe

Table of Contents

Cover

Title Page

Preface

List of Notations

1 Introduction

1.1 Objective and Target Audience

1.2 Fire Safety

1.3 Performance‐based Design

1.4 Structural Fire Engineering

1.5 Purpose of this Book

1.6 Units

1.7 Organization of Chapters

2 Fire Safety in Buildings

2.1 Fire Safety Objectives

2.2 Process of Fire Development

2.3 Conceptual Framework for Fire Safety

2.4 Fire Resistance

2.5 Controlling Fire Spread

2.6 Building Construction for Fire Safety

2.7 Assessment and Repair of Fire Damage

3 Fires and Heat

3.1 Fires in General

3.2 Combustion

3.3 Fire Initiation

3.4 Pre‐flashover Fires

3.5 Flashover

3.6 Post‐flashover Fires

3.7 Design Fires

3.8 Other Factors

3.9 Heat Transfer

3.10 Worked Examples

4 Fire Severity and Fire Resistance

4.1 Providing Fire Resistance

4.2 Fire Severity

4.3 Equivalent Fire Severity

4.4 Fire Resistance

4.5 Fire Resistance Tests

4.6 Specifying Fire Resistance

4.7 Fire Resistance of Assemblies

4.8 Worked Examples

5 Design of Structures Exposed to Fire

5.1 Structural Design at Normal Temperatures

5.2 Loads

5.3 Structural Design in Fire Conditions

5.4 Material Properties in Fire

5.5 Design of Individual Members Exposed to Fire

5.6 Design of Structural Assemblies Exposed to Fire

5.7 Worked Examples

6 Steel Structures

6.1 Behaviour of Steel Structures in Fire

6.2 Steel Temperature Prediction

6.3 Protection Systems

6.4 Mechanical Properties of Steel at Elevated Temperature

6.5 Design of Steel Members Exposed to Fire

6.6 Bolted and Welded Connections

6.7 Cast‐iron Members

6.8 Design of Steel Buildings Exposed to Fire

6.9 Worked Examples

7 Concrete Structures

7.1 Behaviour of Concrete Structures in Fire

7.2 Concrete Materials in Fire

7.3 Spalling of Cover Concrete

7.4 Concrete and Steel Reinforcing Temperatures

7.5 Mechanical Properties of Concrete at Elevated Temperatures

7.6 Design of Concrete Members Exposed to Fire

7.7 Worked Examples

8 Composite Structures

8.1 Fire Resistance of Composite Elements

8.2 Assessing Fire Resistance

8.3 Behaviour and Design of Individual Composite Members in Fire

8.4 Design of Steel and Composite Buildings Exposed to Fire

8.5 Worked Example

9 Timber Structures

9.1 Description of Timber Construction

9.2 Wood Temperatures

9.3 Mechanical Properties of Wood

9.4 Charring Rate

9.5 Design for Fire Resistance of Heavy Timber Members

9.6 Timber Connections in Fire

9.7 Worked Examples

10 Light Frame Construction

10.1 Summary of Light Frame Construction

10.2 Gypsum Plaster Board

10.3 Fire Behaviour

10.4 Fire Resistance Ratings

10.5 Design for Separating Function

10.6 Design for Load‐bearing Capacity

10.7 Steel Stud Walls

10.8 Timber Joist Floors

10.9 Timber Trusses

10.10 Construction Details

10.11 Lightweight Sandwich Panels

11 Advanced Calculation Methods

11.1 Types of Advanced Calculation Methods

11.2 Fire Models

11.3 Thermal Response Models

11.4 Advanced Structural Models

11.5 Advanced Hand Calculation Methods

11.6 Finite Element Methods for Advanced Structural Calculations

11.7 Software Packages for Structural and Thermal Fire Analysis

12 Design Recommendations

12.1 Summary of Main Points

12.2 Summary for Main Materials

12.3 Thermal Analysis

12.4 Conclusions

Appendix A: Units and Conversion Factors

Appendix B: Section Factors for Steel Beams

References

Index

End User License Agreement

List of Tables

Chapter 02

Table 2.1 Summary of periods of typical fire development

Table 2.2 Approximate melting temperature of materials

Chapter 03

Table 3.1 Net calorific values of some combustible materials (in MJ/kg)

Table 3.2 Burning rates for some liquid and solid fuels

Table 3.3 Fire growth rates for

t

‐squared fires

Table 3.4 ASTM E119 and ISO 834 time and temperature values

Table 3.5 Fire growth rate for different occupancies

Table 3.6 Thermal properties of some common materials

Chapter 04

Table 4.1 Three methods for comparing fire severity with fire resistance

Table 4.2 Design combinations for verifying fire resistance

Table 4.3 Values of

k

c

or

k

b

in the time equivalent formulae

Table 4.4 Failure criteria for construction elements

Chapter 05

Table 5.1 ASTM E119 classification for restrained and unrestrained construction

Chapter 06

Table 6.1 Spreadsheet calculation for temperatures of unprotected steel sections

Table 6.2 Thermal properties of insulation materials

Chapter 07

Table 7.1 Generic fire resistance ratings for concrete columns

Chapter 08

Table 8.1 Value of factor

f

for fire resistance of concrete filled steel columns (Kodur, 1999)

Chapter 09

Table 9.1 Charring rates from Eurocode 5

Table 9.2 Fire resistance of unprotected connections with side members of wood

Chapter 10

Table 10.1 Minimum gypsum board thickness (mm) to give fire resistance ratings for cavity walls and floors

Table 10.2 Component additive method in the Canadian code

Chapter 11

Table 11.1 Available approaches for the three components of structural fire design

Chapter 12

Table 12.1 Summary of fire design methods for the main structural materials

Table 12.2 Summary of thermal calculation methods for the main structural materials

List of Illustrations

Chapter 01

Figure 1.1 Typical hierarchical relationship for performance‐based design

Chapter 02

Figure 2.1 Time–temperature curve for full process of fire development

Figure 2.2 Hotel fire where spread of smoke remote from the fire killed 84 people (MGM Grand Hotel, Las Vegas, 1980).

Figure 2.3 Overview of scenario analysis

Figure 2.4 Fire Safety Concepts Tree.

Figure 2.5 Example of fire resistance in a severe warehouse fire: (a) view of the fire after roof collapse; (b) collapsed steel beams and damaged concrete masonry wall after the fire; and (c) light timber framed wall separating the warehouse from the offices

Figure 2.6 Fire on the 12th floor of a 62 storey building, illustrating the importance of providing both containment and structural stability.

Figure 2.7 Spread of smoke and fire through a ceiling cavity

Figure 2.8 The masonry walls of a large department store after a severe fire (Ballantynes department store, New Zealand, 1947).

Figure 2.9 Fire protection to service penetrations through a fire resisting floor

Figure 2.10 Fire separation of vertical services

Figure 2.11 Fire spread from storey to storey

Figure 2.12 Fire stopping between slab and curtain wall

Figure 2.13 Severe fire in a department store.

Figure 2.14 Fire spread by flaming brands

Figure 2.15 Fire spread from a low building to a taller building

Figure 2.16 Fire damage following the San Francisco earthquake, 1906.

Figure 2.17 One of many severe fires which destroyed buildings after the Hanshin‐Awaji earthquake, Kobe, Japan, 1995

Chapter 03

Figure 3.1 A burning sofa in a furniture calorimeter test. If this sofa was burning in a room, the room would be full of toxic smoke

Figure 3.2 Heat release rate for furniture items.

Figure 3.3 Early stages of fire in a room

Figure 3.4 Smoke damage following a pre‐flashover fire in a room, indicating the thickness of the hot upper layer during the fire

Figure 3.5 Heat release rate for

t‐

squared fires

Figure 3.6 Heat release rates for a fire load of 3200 MJ

Figure 3.7 Combined design fire for two burning objects

Figure 3.8 Post‐flashover fire on the top floor of a multi‐storey office building. The flames coming out of the windows indicate that this fire is ventilation controlled

Figure 3.9 Window flows for ventilation controlled fire

Figure 3.10 Calculation of ventilation factor for more than one window

Figure 3.11 Experimental time temperature curves.

Figure 3.12 Maximum temperature in the burning period of experimental fires.

Figure 3.13 Time–temperature curves for different ventilation factors and fuel loads (MJ/m

2

total surface area).

Figure 3.14 Time–temperature curves for varying ventilation and constant fuel load (MJ/m

2

total surface area)

Figure 3.15 Time–temperature curves for varying fuel load (MJ/m

2

total surface area) and constant ventilation

Figure 3.16 Heat balance for a post‐flashover room fire

Figure 3.17 Burning rate used for calculating Swedish curves.

Figure 3.18 Design fire with constant temperature

Figure 3.19 Nominal time–temperature curves for post‐flashover fires

Figure 3.20 Parametric time–temperature curves. Fuel load is 400, 800 and 1200 MJ/m

2

floor area

Figure 3.21 Vent flows for room with ceiling opening

Figure 3.22 Nomogram for calculating the ventilation factor for roof vents.

Figure 3.23 Vent flows for two windows, with wind blowing

Figure 3.24 Progressive burning in a deep room with one window

Figure 3.25 Temperatures during progressive burning in a deep room.

Figure 3.26 Radiation from one surface to another

Figure 3.27 Emitting and receiving surfaces

Chapter 04

Figure 4.1 Behaviour of a steel beam in fire: (a) temperature increase; (b) loss of strength

Figure 4.2 Fire models and structural response models.

Figure 4.3 Equivalent fire severity on equal area basis

Figure 4.4 Equivalent fire severity on temperature basis

Figure 4.5 Equivalent fire severity on load‐bearing capacity basis

Figure 4.6 Typical furnace for full‐scale fire resistance testing of walls

Figure 4.7 Floor furnace with a heavy surrounding beam for providing axial restraint to the test specimens.

Figure 4.8 Detail of loading arrangement for fire testing of floors

Figure 4.9 Harmathy’s ten rules of fire endurance.

Figure 4.10 Flow chart for calculating strength of a structure exposed to fire

Figure 4.11 A special furnace for fire resistance testing of columns, with an unprotected steel column ready for testing.

Figure 4.12 Fire resistance test of two doors. The door on the left has had an integrity failure, as shown by penetration of flames and hot gases.

Chapter 05

Figure 5.1 Internal strains in a simply supported beam

Figure 5.2 Stress–strain relationships and internal flexural stresses for steel, concrete and timber beams

Figure 5.3 Probabilistic design concept

Figure 5.4 Member failure in fire, due to internal stresses exceeding material strength

Figure 5.5 Testing regimes for determining mechanical properties of materials at elevated temperatures.

Figure 5.6 Creep in structural materials: (a) creep under normal conditions; (b) creep at elevated temperatures

Figure 5.7 Column buckling. (a) Effect of member length on compressive load capacity. (b) Steel column which has buckled during fire exposure.

Figure 5.8 Bending moment diagrams for a simply supported beam

Figure 5.9 Frame deformations in the lower floors of a multi‐storey frame resulting from a fire on the ground floor.

Figure 5.10 Multi‐storey apartment building after a gas explosion caused disproportionate collapse to upper floors.

Figure 5.11 Moment–curvature relationship for a beam of ductile material

Figure 5.12 Behaviour of simply supported and continuous beams

Figure 5.13 Moment redistribution to equal positive and negative moments

Figure 5.14 Moment redistribution to unequal positive and negative moments

Figure 5.15 Bending moment diagram for a two‐span continuous beam

Figure 5.16 Plastic deformation of a fixed end beam

Figure 5.17 Plastic failure mechanisms for an indeterminate beam

Figure 5.18 Effect of axial restraint force on bending moment diagram

Figure 5.19 Free body diagram of reinforced concrete beam with axial restraint

Figure 5.20 Location of axial thrust for several support conditions.

Chapter 06

Figure 6.1 Typical fire damage to unprotected steel frames in an industrial building

Figure 6.2 (a) Severe fire in a theatre, showing collapsed steel roof trusses in the foreground; the gallery seating which did not collapse is visible in the upper background. (b) Buckling of a compression member in the heavy steel truss supporting the gallery seating; this truss is close to failure, but did not collapse. (c) Holes punched through a reinforced concrete wall by thermal expansion of the heavy steel truss supporting the gallery seating

Figure 6.3 Temperature contours in a heavy steel section exposed to fire.

Figure 6.4 Definition of section factor in the Eurocode.

Figure 6.5 Specific heat of steel as a function of temperature.

Figure 6.6 Thermal conductivity of steel as a function of temperature.

Figure 6.7 Typical steel temperatures for unprotected and protected steel beams exposed to: (a) the standard fire; (b) a parametric fire

Figure 6.8 Fire exposure of external steel columns.

Figure 6.9 Steel beam and column protected with board materials

Figure 6.10 Detail of steel beam protected with board materials.

Figure 6.11 Box protection being placed on a steel column using sheet material

Figure 6.12 Sprayed‐on fire protection to steel beams supporting precast concrete floor slabs

Figure 6.13 Flame protection of exterior steel beam.

Figure 6.14 Creep of steel tested in tension.

Figure 6.15 Stress–strain curves for typical hot rolled steel at elevated temperature.

Figure 6.16 Stress–strain curves for prestressing steel at elevated temperature.

Figure 6.17 Stress–strain curves for steel illustrating yield strength and proof strength

Figure 6.18 Scatter in published results of hot‐rolled steel.

Figure 6.19 Scatter in published results of cold‐worked steel.

Figure 6.20 Design curves for reduction in yield strength and modulus of elasticity of with temperature

Figure 6.21 Reduction in yield strength and modulus of elasticity with temperature.

Figure 6.22 Stress–strain curve with elasto‐plastic approximation

Figure 6.23 Internal forces in a steel tensile member

Figure 6.24 Moment–deflection relationship for a steel beam

Figure 6.25 Internal forces in a steel flexural member

Figure 6.26 Failure mechanisms for simply supported and continuous beams

Figure 6.27 Effective lengths of fire exposed columns in a multi‐storey frame: (a) section through the building; (b) deformation mode at room temperature; and (c) deformation mode at elevated temperature.

Figure 6.28 Temperature–time relationship of protected and unprotected steel in the standard fire

Chapter 07

Figure 7.1 Non‐structural fire damage to a typical reinforced concrete office building

Figure 7.2 (a) A multi‐storey office building engulfed in flames. The reinforced concrete structure did not collapse in the fire (Sao Paolo, Brazil, 1972). (b) Severe spalling of a reinforced concrete wall in the fire

Figure 7.3 Major structural damage to a multi‐storey reinforced concrete department store (Athens, Greece, 1980).

Figure 7.4 Local spalling at the corner of a concrete beam

Figure 7.5 Temperatures in concrete slabs exposed to the standard fire.

Figure 7.6 Temperature contours in concrete beams exposed to the standard fire.

Figure 7.7 Temperatures inside concrete slabs exposed to design fires: (a) time–temperature curves; (b) peak temperatures.

Figure 7.8 Thermal conductivity of concrete. LWC, lightweight concrete; NWC, normal weight concrete.

Figure 7.9 Specific heat of concrete. LWC, lightweight concrete; NWC, normal weight concrete.

Figure 7.10 Variation of thermal elongation with temperature. LWC, lightweight concrete; NWC, normal weight concrete.

Figure 7.11 Total deformation in different types of concrete during heating.

Figure 7.12 Creep in concrete 1 day after loading at 10% of the initial cold strength.

Figure 7.13 Stress–strain relationships for concrete at elevated temperatures.

Figure 7.14 Reduction in compressive strength with temperature.

Figure 7.15 Design values for the reduction of compressive strength with temperature. LWC, lightweight concrete; NWC, normal weight concrete.

Figure 7.16 Design values (

k

E,T

) for reduction of modulus of elasticity with temperature

Figure 7.17 Simply supported reinforced concrete slab exposed to fire

Figure 7.18 Simply supported reinforced concrete tee‐beam exposed to fire

Figure 7.19 Simply supported non‐composite beam exposed to fire

Figure 7.20 Support region of continuous concrete slab exposed to fire

Figure 7.21 Support region of continuous concrete beam exposed to fire

Figure 7.22 Unsatisfactory axial restraint in flange‐supported double‐tee floor slab

Figure 7.23 Mid‐span deflection of reference specimens.

Figure 7.24 Nomogram for thrust in concrete members.

Figure 7.25 Beam for Worked Example 7.2

Figure 7.26 Beam for Worked Example 7.3

Figure 7.27 Beam for Worked Example 7.4

Chapter 08

Figure 8.1 Composite construction with concrete slab on steel deck and steel beam

Figure 8.2 Composite construction with steel members protected by concrete

Figure 8.3 Typical examples of composite flooring systems: (a) trapezoidal decking system; (b) re‐entrant decking system

Figure 8.4 Steel column protected with concrete encasement

Figure 8.5 Steel column protected with concrete between the flanges

Figure 8.6 Concrete filled tubular steel column

Figure 8.7 Generalized composite beam for the bending moment capacity method.

Figure 8.8 Composite construction with light steel joists: (a) open web steel joist; (b) rolled steel joist

Figure 8.9 Buckling curves for the design of composite compression members.

Figure 8.10 Typical axial deformation of CFT column exposed to a standard fire.

Figure 8.11 Local buckling of an unprotected steel column during a fire in a building under construction (Broadgate, London, 1990) (SCI, 1991)

Figure 8.12 (a) Flames coming from the window during a post‐flashover fire in the Cardington fire test building.

Figure 8.13 Single‐storey portal frame industrial building

Figure 8.14 Heat release rate for fire in an industrial building

Figure 8.15 Axial thrust in rafter of portal frame during fire.

Figure 8.16 Failure of an unreinforced brick masonry wall of an industrial building; the wall was pushed outwards by thermal expansion of the steel portal frames, which later collapsed inwards.

Figure 8.17 Outward collapse of a precast concrete wall panel during a fire in an industrial building; such a collapse would endanger firefighters and allow fire spread.

Figure 8.18 Failure mechanism for single‐storey industrial building in fire.

Chapter 09

Figure 9.1 Typical cross laminated timber panel

Figure 9.2 (a) Severe fire damage to an industrial building with curved glulam portal frames. (b) One of the beams repaired for re‐use by sandblasting.

Figure 9.3 Curved glulam roof beams after repair following a severe fire.

Figure 9.4 Char layer and pyrolysis zone in a timber beam.

Figure 9.5 Variation of thermal conductivity of wood and char layer with temperature

Figure 9.6 Variation of specific heat of wood and the char layer with temperature

Figure 9.7 Loading of wood in different directions

Figure 9.8 Stress–strain relationships for clear wood

Figure 9.9 Effect of temperature on modulus of elasticity parallel to grain (Eurocode 5).

Figure 9.10 Effect of temperature on strength in tension and compression parallel to grain, and in shear (Eurocode 5).

Figure 9.11 Effect of temperature on modulus of elasticity perpendicular to grain.

Figure 9.12 Shear stresses and shear failure in a timber beam

Figure 9.13 Stress–strain relationships for wood at elevated temperatures

Figure 9.14 Charring rate as affected by density and moisture content.

Figure 9.15 Depth of char from North American recommendations

Figure 9.16 Residual cross section of timber beam exposed to fire.

Figure 9.17 Charring depth versus time for wood with a protective layer. (a) Charring starts after the protective layer falls off. (b) The protective layer falls off too soon to be of any use. (c) Charring starts behind the protective layer before it falls off.

Figure 9.18 (a) Temperature profile below the char layer. (b) Reduction in strength of wood below the char layer. (c) Reduction in modulus of elasticity below the char layer

Figure 9.19 Fire resistance test of glulam beams; the beams span a 4 m long furnace with loads applied using concrete blocks

Figure 9.20 Residual cross section of a large glulam beam after a fire test.

Figure 9.21 Design concepts for large timber members

Figure 9.22 Three‐ and four‐sided fire exposure of beams

Figure 9.23 Tongue and groove decking and solid plank decking exposed to fire

Figure 9.24 Effect of gap width on charring.

Figure 9.25 Charring model for hollow core timber floors: (a) charring phase 1; (b) charring phase 2.

Figure 9.26 Typical connections in timber structures

Figure 9.27 Bolted connection between timber members, after fire exposure

Figure 9.28 Truss plate connection between timber members, after fire exposure

Figure 9.29 Tension tests of nailed and bolted joints.

Figure 9.30 Possible failure modes of fasteners.

Figure 9.31 Protection of metal fasteners in BS 5268.

Figure 9.32 Effect of elevated temperature on strength of finger joints.

Chapter 10

Figure 10.1 Typical light timber house framing

Figure 10.2 Multi‐storey light timber frame construction

Figure 10.3 Light timber frame floor construction

Figure 10.4 Light steel framed wall construction

Figure 10.5 Specific heat of gypsum plaster (Sultan, 1996). Data obtained with permission from

Fire Technology

.

Figure 10.6 Thermal conductivity of gypsum plaster (Sultan, 1996). Data obtained with permission from

Fire Technology

.

Figure 10.7 Full‐scale fire resistance test of a light timber frame wall

Figure 10.8 Specification for light timber frame proprietary rating.

Figure 10.9 Temperature profiles within a cavity wall during a standard fire resistance test (Thomas, 1997)

Figure 10.10 Heat transfer paths through separating multiple‐layered construction.

Figure 10.11 Fire resistance test of a light timber frame wall

Figure 10.12 Residual charred studs of a light timber frame wall after a full‐scale fire resistance test

Figure 10.13 Measured char profiles on timber studs. (a) Stud in empty cavity, protected with 14.5 mm gypsum board. (b) Stud in insulated cavity with no protection on the fire‐exposed face.

Figure 10.14 Notional residual stud in a light timber wall after fire exposure

Figure 10.15 Detail of top end of timber stud (a) before and (b) during a fire test

Figure 10.16 Full‐scale fire resistance test of a light steel frame wall. The wall has deflected inwards towards the furnace due to thermal bowing

Figure 10.17 Linear interpolation for fire resistance of load‐bearing steel stud walls

Figure 10.18 Failure stresses in timber floor joists at normal temperatures (a and b) and exposed to fire from below (c and d).

Figure 10.19 Nailing of gypsum board to 38 mm wide timber stud

Figure 10.20 Gap between gypsum boards caused by shrinkage of gypsum plaster

Figure 10.21 Gap between gypsum board and stud using a resilient rail

Figure 10.22 Distance between screws and edge of gypsum board increased with the use of resilient rails.

Figure 10.23 Protection of electrical fitting in cavity wall

Figure 10.24 Party wall between apartments.

Figure 10.25 Fire stopping details.

Figure 10.26 Flexural behaviour of sandwich panels.

Figure 10.27 Support of sandwich panel wall (a) during initial fire exposure and (b) after the foam insulation has melted.

Figure 10.28 (a) Fire damage to foamed plastic sandwich panels in a factory fire. The building to the right of the photo was completely destroyed by the fire. (b) Steel skins of sandwich panel roofing, draped over the supporting structure after the fire

Chapter 11

Figure 11.1 Localized fires (IStructE, 2007).

Figure 11.2 Comparison of simplified calculation method and advanced thermal analysis for a solid steel bar. (a) Heated cross section with locations of temperature readings (distances in millimetres). (b) Comparison of test results and thermal analysis

Figure 11.3 Numerical simulation results of one‐dimensional heating through timber, using the latent heat of vaporization (enthalpy) approach for a 6 mm × 6 mm mesh size (Werther

et al

., 2012)

Figure 11.4 Numerical simulation results of one‐dimensional heating through timber, using a 6 mm × 6 mm mesh size, and the specific heat capacity approach for the ANSYS and ABAQUS models (Werther

et al

., 2012)

Figure 11.5 Tensile membrane action (Abu, 2009)

Figure 11.6 Schematic diagram of the Bailey‐BRE method (Abu, 2009): (a) composite floor slab; (b) slab panel

Figure 11.7 In‐plane stress distribution for the Bailey‐BRE method.

Figure 11.8 Collapse mechanisms of composite slab panels, including failure of protected beams (Duchow and Abu, 2014)

Figure 11.9 Local buckling of beam bottom flange in Cardington Test 7.

Figure 11.10 Axial force in a restrained composite beam.

Figure 11.11 Connection failure, during cooling, in Cardington tests.

Figure 11.12 Column flange buckling in Cardington Test 7.

Figure 11.13 Stress–strain relationship for structural steel in fire from Eurocode 3 Part 1.2.

Figure 11.14 Stress–strain relationships for S275 structural steel at high temperatures (based on Eurocode 3 Part 1.2 model).

Figure 11.15 Ramberg–Osgood stress–strain relationship for S250 structural steel in fire.

Figure 11.16

S

tress–strain relationship for concrete in fire from Eurocode 4 Part 1.2.

Figure 11.17 Stress–strain relationships for concrete of compressive strength 40 MPa at high temperatures (based on Eurocode 4 Part 1.2).

Figure 11.18 Importance of the tensile strength of concrete in numerical models of slabs at large deflections (Lim

et al

., 2004). (a) Deflection profile of 100 mm thick slab. (b) Numerical modelling results comparison

Figure 11.19 Examples of finite elements used in structural analysis.

Figure 11.20 Discretized cross section of a reinforced concrete beam, showing positions of reinforcing bars. (a) Original beam cross section. (b) Discretized beam cross section

Figure 11.21 Three‐dimensional model of a composite connection.

Figure 11.22 Modelling composite slabs with shell elements. (a) Profile of a Hibond composite slab. (b) Layered shell element

Figure 11.23 Options for modelling composite slabs in fire conditions: (a) full depth; (b) average depth; and (c) thin continuous depth

Figure 11.24 Component modelling of spring connections. 1, Endplate in bending; 2, column flange in bending; 3, bolts in tension; 4, column web in compression; and 5, slip and shear of bolts.

Figure 11.25 Three‐dimensional model of a fin plate connection.

Appendix B

Figure B.1 Geometry of hot rolled section

Guide

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STRUCTURAL DESIGN FOR FIRE SAFETY

Second Edition

Andrew H. Buchanan & Anthony K. Abu

University of Canterbury, New Zealand

This edition first published 2017© 2017 John Wiley & Sons, Ltd

First Edition published in 2001

Registered OfficeJohn Wiley & Sons, Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom

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Library of Congress Cataloging‐in‐Publication Data

Names: Buchanan, Andrew Hamilton, 1948– author. | Abu, Anthony Kwabena, 1980– author.Title: Structural design for fire safety / Andrew H. Buchanan, Anthony K. Abu.Description: Second edition. | Chichester, West Sussex, United Kingdom : John Wiley & Sons Inc., 2017. | Includes bibliographical references and index.Identifiers: LCCN 2016032579 | ISBN 9780470972892 (cloth) | ISBN 9781118700396 (epub)Subjects: LCSH: Building, Fireproof. | Structural engineering.Classification: LCC TH1065 .B89 2017 | DDC 693.8/2–dc23LC record available at https://lccn.loc.gov/2016032579

A catalogue record for this book is available from the British Library.

Cover image: AUSTRIA FIRE RETIREMENT HOME     (Media ID: 20080209000077529215)     Credit: EPA | Source: APA | Trans Ref: EGG03

Preface

Fires in buildings have always been a threat to human life and property. The threat increases as larger numbers of people live and work in bigger buildings throughout the world. Professor Buchanan’s interest in structural fire engineering was initiated by Professor Brady Williamson in the 1970s at the University of California at Berkeley, and developed during his subsequent career as a practising structural engineer, then as an academic. Dr Abu was introduced to the subject by Professor Ian Burgess and Professor Roger Plank at the University of Sheffield in 2004, and has since worked with a number of consultants in the field.

New Zealand became one of the first countries to adopt a performance‐based building code in the late 1980s, stimulating a demand for qualified fire engineers. This led to the establishment of a Master’s Degree in Fire Engineering at the University of Canterbury, where one of the core courses is structural fire engineering, now taught by Dr Abu. The lecture notes for that course have grown into this book. Many masters and PhD students have conducted research which has contributed to our knowledge of fire safety, and much of that is reported here.

Professor Buchanan and Dr Abu have both been involved in many problems of fire safety and fire resistance, designing fire resisting components for buildings, assisting manufacturers of fire protecting materials, and serving on national fire safety committees.

Preparation of this book would not have been possible without the help of many people. We wish to thank Charley Fleischmann, Michael Spearpoint, Peter Moss, Rajesh Dhakal and other colleagues in the Department of Civil and Natural Resources Engineering at the University of Canterbury, and a large number of graduate students.

Many people provided helpful comments on the text, figures, and underlying concepts, especially Philip Xie, Melody Callahan, and a large number of friends and colleagues in the international structural fire engineering community.

This book is only a beginning; the problem of fire safety is very old and will not go away. We hope that this book helps to encourage rational improvements to structural fire safety in buildings throughout the world.

The second edition has been a long time coming because of devastating earthquakes in Christchurch and other unforeseen difficulties. We hope that it has been worth the wait.

Andrew H. Buchanan and Anthony K. AbuUniversity of Canterbury, New Zealand

List of Notations

α

Fire intensity coefficient

MW/s

2

α

Thermal diffusivity

m

2

/s

α

Ratio of hot wood strength to cold wood strength

α

h

Horizontal openings ratio

α

v

Vertical openings ratio

β

Target reliability

β

Measured charring rate

mm/min

β

1

Effective charring rate if corner rounding ignored

mm/min

β

n

Nominal charring rate

mm/min

β

par

Charring rate for parametric fire exposure

mm/min

δ

Beam deflection

mm

Δ

Deflection

mm

Δ

L

Maximum permitted displacement

mm

Δ

0

Mid‐span deflection of the reference specimen

mm

χ

Buckling factor

ε

Strain

ε

i

Initial strain

ε

σ

Stress‐related strain

ε

cr

Creep strain

ε

th

Thermal strain

ε

tr

Transient strain

ε

Resultant emissivity

ε

e

Emissivity of the emitting surface

ε

r

Emissivity of the receiving surface

φ

Configuration factor

Φ

Strength reduction factor

Φ

f

Strength reduction factor for fire design

k

Elastic curvature

1/m

γ

M

Partial safety factor for material

γ

G

Partial safety factor for dead load

γ

Q

Partial safety factor for live load

η

Temperature ratio

θ

Plastic hinge rotation

rad

θ

Radiating angle

rad

ρ

Density

kg/m

3

σ

Stefan–Boltzmann constant

kW/m

2

K

4

σ

Stress

MPa

ν

p

Regression rate

m/s

ξ

Reduction coefficient for charring of decks

a

Depth of heat affected zone below char layer

mm

a

Depth of rectangular stress block

mm

a

Distance of the maximum positive moment from the support

m

a

f

Depth of stress block, reduced by fire

mm

a

fi

Thickness of wood protection to connections

mm

A

Cross‐sectional area

mm

2

, m

2

A

f

Floor area of room

m

2

A

fi

Area of member, reduced by fire

mm

2

, m

2

A

fuel

Exposed surface area of burning fuel

m

2

A

h

Area of horizontal ceiling opening

m

2

A

1

Area of radiating surface 1

m

2

A

r

Cross‐sectional area reduced by fire

mm

2

, m

2

A

s

Area of reinforcing steel

mm

2

A

t

Total internal surface area of room

m

2

A

v

Window area

m

2

b

Breadth of beam

mm

b

f

Breadth of beam reduced by fire

mm

b

√Thermal inertia = √(

kρc

p

)

Ws

0.5

/m

2

K

b

v

Vertical opening factor

B

Breadth of window opening

m

c

Thickness of char layer

mm

c

p

Specific heat

J/kg K

c

v

Concrete cover to reinforcing

mm

C

Compressive force

kN

C

Contraction

mm

d

Depth of beam, effective depth of concrete beam

mm

d

Thickness of timber deck

mm

d

Diameter of circular column or width of square column

mm

d

f

Depth of beam reduced by fire

mm

d

i

Thickness of insulation

mm

D

Length of short side of compartment

m

D

Deflection

mm

D

Thickness of slab of burning wood

m

D

b

Reinforcing bar diameter

mm

e

Eccentricity

mm

e

f

Fuel load energy density (per unit floor area)

MJ/m

2

e

t

Fuel load energy density(per unit area of internal room surfaces)

MJ/m

2

E

Modulus of elasticity

GPa

E

Total energy contained in fuel

MJ

E

k

Characteristic earthquake load

f

Factor in concrete‐filled steel column equation

f

Stress

MPa

f

*

Calculated stress in member

MPa

f

*

t

Calculated tensile stress for working stress design

MPa

f

a

Allowable design stress for working stress design

MPa

f

b

Characteristic flexural strength

MPa

f

b.f

Characteristic flexural strength in fire conditions

MPa

f

c

Crushing strength of the material

MPa

f’

c

Characteristic compressive strength

MPa

f’

c,T

Compressive strength at elevated temperature

MPa

f

t

Characteristic tensile strength

MPa

f

tw

Long term allowable tensile strength

MPa

f

t,f

Characteristic tensile strength in fire conditions

MPa

f

y

Yield strength at 20 °C

MPa

f

y,T

Yield strength at elevated temperature

MPa

F

Surface area of unit length of steel

m

2

F

c

Crushing load of column

kN

F

crit

Critical buckling load of column

kN

F

v

Ventilation factor (

A

v

√

H

v

/

A

t

)

m

0.5

g

Acceleration of gravity

m/s

2

g

Char parameter

G

Dead load

G

k

Characteristic dead load

h

Slab thickness

mm

h

Initial height of test specimen

mm

h

Height from mid‐height of window to ceiling

m

h

c

Convective heat transfer coefficient

W/m

2

K

h

r

Radiative heat transfer coefficient

W/m

2

K

h

t

Total heat transfer coefficient

W/m

2

K

H

Height of radiating surface

m

H

p

Heated perimeter of steel cross section

m

H

r

Height of room

m

H

v

Height of window opening

m

Δ

H

c

Calorific value of fuel

MJ/kg

Δ

H

c

Heat of combustion of fuel

MJ/kg

Δ

H

c,n

Effective calorific value of fuel

MJ/kg

I

Moment of inertia

mm

4

jd

Internal lever arm in reinforced concrete beam

mm

k

Growth parameter for t

2

fire

s/√MW

k

Thermal conductivity

W/mK

k

i

Thermal conductivity of insulation

W/mK

k

a

Ratio of allowable strength to ultimate strength

k

b

Compartment lining parameter

min m

2

/MJ

k

c

Compartment lining parameter

min m

2.25

/MJ

k

f

Strength reduction factor for heated wood

k

mean

Factor to convert allowable stress to mean failure stress

k

c,T

Reduction factor for concrete strength

k

E,T

Reduction factor for modulus of elasticity

k

y,T

Reduction factor for yield strength

k

d

Duration of load factor for wood strength

k

sh

Correction factor for shadow effect

k

20

Factor to convert 5th percentile to 20th percentile

K

Effective length factor for column

l

1

,

l

2

Dimensions of floor plan

m

L

Fire load (wood mass equivalent)

kg

L

Length of structural member

mm

L

f

Factored load for fire design

L

u

Factored load for ultimate limit state

L

w

Load for working stress design

L

v

Heat of gasification

MJ/kg

m

c

Moisture content as percentage by weight

%

Rate of burning

kg/s

M

Mass per unit length of steel cross section

kg

M

Mass of fuel

kg

M

Bending moment

kN.m

M

−

Negative bending moment

kN.m

M

*

cold

Design bending moment in cold conditions

kN.m

M

*

fire

Design bending moment in fire conditions

kN.m

M

*

fire,red

Design bending moment of plastic hinge in fire conditions

kN.m

M

f

Total mass of fuel available for combustion

kg

M

f

Flexural capacity in fire conditions

kN.m

M

n

Flexural capacity in cold conditions

kN.m

M

y

Moment capacity at the start of yielding

kN.m

M

p

Moment capacity of plastic hinge

kN.m

M

p

+

Positive moment capacity of plastic hinge

kN.m

M

p

−

Negative moment capacity of plastic hinge

kN.m

M

u

Moment capacity

kN.m

N

Axial load, axial load capacity

kN

N

c

Crushing strength capacity

kN

N

crit

Critical buckling strength

kN

N

n

Axial load capacity

kN

N

w

Axial tensile force for working stress design

kN

N

u

Axial load capacity

kN

N

f

Axial load capacity in fire conditions

kN

N

*

Design axial force

kN

N

*

fire

Design axial force in fire conditions

kN

p

Perimeter of fire exposed cross section

m

q

Surface burning rate

kg/s/m

2

Heat flux

W/m

2

q

i

Incident radiation reaching fuel surface

kW/m

2

Heat produced by combustion of fuel

kW

Heat carried out of the opening by convection of hot gases and smoke

kW

Heat radiated through the opening

kW

Heat conducted into the surrounding structure

kW

Q

Rate of heat release

MW

Q

fo

Critical heat release rate for flashover

MW

Q

p

Peak heat release rate

MW

Q

fuel

Rate of heat release for fuel controlled fire

MW

Q

vent

Rate of heat release for ventilation controlled fire

MW

Q

Live load

Q

k

Characteristic live load

r

Radius of gyration

mm

r

Radius of charred corner

mm

r

Distance from radiator to receiver

m

r

load

Load ratio

R

Load capacity

R

a

Ratio of actual to allowable load at normal temperature

R

f

Minimum load capacity reached during the fire

R

code

Load capacity reached at time t

code

R

cold

Load capacity in cold conditions

R

fire

Load capacity in fire conditions

s

Thickness of compartment lining material

m

s

lim

Limit thickness

m

s

Heated perimeter

mm

S

Plastic section modulus

mm

3

S

k

Characteristic snow load

SW

Self‐weight

t

Thickness of steel plate

mm

t

Time

h, min or s

t

*

Fictitious time

h

t

e

Equivalent duration of exposure to the standard fire to a complete burnout of a real fire in the same room

min

t

fail

Time to failure of the element when exposed to the standard fire

t

b

Duration of burning

min

t

d

Duration of burning period (ventilation controlled)

h

t

fo

Time to flashover

s

t

lim

Duration of burning period (fuel controlled)

h

t

max

Time to reach maximum temperature

h

t*

max

Fictitious time to reach maximum temperature

h

t

code

Time of fire resistance required by the building code

min

t

r

Time of fire resistance

min

t

s

Time of fire severity

min

T

Thermal thrust

kN

T

Temperature

°C

T

e

Absolute temperature of the emitting surface

K

T

r

Absolute temperature of the receiving surface

K

T

g

Gas temperature

°C

T

i

Initial temperature of wood

°C

T

lim

Limiting temperature

°C

T

code

Temperature reached at time t

code

°C

T

fail

Temperature of failure

°C

T

max

Maximum temperature

°C

T

p

Temperature of wood at start of charring

°C

T

0

Ambient temperature

°C

T

y

Tensile force at yield

kN

U

Load effect

U

f

Load effect in fire conditions

U

*

Design force for ultimate limit state design

U

*

fire

Design force in fire conditions

V

Volume of unit length of steel member

m

3

V

f

Shear capacity in fire conditions

kN

V

Shear capacity

kN

V

*

Design shear force

kN

V

*

f

Design shear force in fire conditions

kN

w

Ventilation factor

w

Uniformly distributed load on beam

kN/m

w

c

Uniformly distributed load on beam, in cold conditions

kN/m

w

f

Uniformly distributed load on beam, in fire conditions

kN/m

W

Length of long side of compartment

m

W

Width of radiating surface

m

W

k

Characteristic wind load

x

Distance in the direction of heat flow

m

x

Height ratio

y

Width ratio

y

b

Distance from the neutral axis to the extreme bottom fibre

(mm)

z

Thickness of zero strength layer

mm

z

Load factor

Z

Elastic section modulus

mm

3

Z

f

Elastic section modulus in fire conditions

mm

3

1Introduction

This book is an introduction to the structural design of buildings and building elements exposed to fire. Structural fire resistance is discussed in relation to overall concepts of building fire safety. The book brings together, from many sources, a large volume of material relating to the fire resistance of building structures. It starts with fundamentals, giving an introduction to fires and fire safety, outlining the important contribution of structural fire resistance to overall fire safety.

Methods of calculating fire severity and achieving fire resistance are described, including fire performance of the main structural materials. The most important parts of the book are the design sections, where the earlier material is synthesised and recommendations are made for rational design of building elements and structures exposed to fires.

This book refers to codes and standards as little as possible. The emphasis is on understanding structural behaviour in fire from first principles, allowing structural fire safety to be provided using rational engineering methods based on national structural design codes.

1.1 Objective and Target Audience

This book is primarily written for practising structural engineers and students in structural engineering who need to assess the structural performance of steel, concrete or timber structures exposed to unwanted fires. A basic knowledge of structural mechanics and structural design is assumed. The coverage of fire science in this book is superficial, but sufficient as a starting point for structural engineers and building designers. For more detail, readers should consult recognised texts such as Quintiere (1998), Karlsson and Quintiere (2000) and Drysdale (2011), and the Handbook of the Society of Fire Protection Engineers (SFPE, 2008). This book will help fire engineers in their discussions with structural engineers, and will also be useful to architects, building inspectors, code officials, firefighters, students, researchers and others interested in building fire safety.

A structural engineer who has followed this book should be able to:

interpret the intentions of code requirements for structural fire safety;

understand the concepts of fire severity and fire resistance;

estimate time–temperature curves for fully developed compartment fires;

design steel, concrete, steel‐concrete composite, or timber structures to resist fire exposure;

assess the fire performance of existing structures.

1.2 Fire Safety

Unwanted fire is a destructive force that causes many thousands of deaths and billions of dollars of property loss each year. People around the world expect that their homes and workplaces will be safe from the ravages of an unwanted fire. Unfortunately, fires can occur in almost any kind of building, often when least expected. The safety of the occupants depends on many factors in the design and construction of buildings, often focusing on the escape of people from burning buildings. Occupant escape and firefighter access is only possible if buildings and parts of buildings will not collapse in a fire or allow the fire to spread. Fire safety science is a rapidly expanding multi‐disciplinary field of study. It requires integration of many different fields of science and engineering, some of which are summarized in this book.

Fire deaths and property losses could be eliminated if all fires were prevented, or if all fires were extinguished at the size of a match flame. Much can be done to reduce the probability of occurrence, but it is impossible to prevent all major fires. Given that some fires will always occur, there are many strategies for reducing their impact, and some combination of these will generally be used by designers. The best proven fire safety technology is the provision of automatic fire sprinklers because they have been shown to have a very high probability of controlling or extinguishing any fire. It is also necessary to provide facilities for the detection and notification of fires, safe travel paths for the movement of occupants and firefighters, barriers to control the spread of fire and smoke, and structures which will not collapse prematurely when exposed to fire. The proper selection, design and use of building materials is very important, hence this book.

1.3 Performance‐based Design

1.3.1 Fundamentals of Performance‐based Design

Until recently, most design for fire safety has been based on prescriptive building codes, with little or no opportunity for designers to take a rational engineering approach. Many countries have recently adopted performance‐based building codes which allow designers to use any fire safety strategy they wish, provided that adequate safety can be demonstrated (Hurley and Bukowski, 2008). In general terms, a prescriptive code states how a building is to be constructed whereas a performance‐based code states how a building is to perform under a wide range of conditions (Custer and Meacham, 1997).

Some prescriptive building codes give the opportunity for performance‐based selection of structural assemblies. For example, if a code specifies a floor with a fire resistance rating of two hours, the designer has the freedom to select from a wide range of approved floor systems which have sufficient fire resistance. This book provides tools for assessing the fire performance of structural elements which have been tested, as well as those with different geometry, loads or fire exposure from those tested.

In the development of new codes, many countries have adopted a multi‐level hierarchical performance‐based code format as shown in Figure 1.1. At the highest levels, there is legislation specifying the overall goals, functional objectives and required performance which must be achieved in all buildings. At a lower implementation level, there is a selection of alternative means of achieving those goals. The three most common options are:

A prescriptive ‘Acceptable Solution’ (sometimes call a ‘deemed‐to‐satisfy’ solution).

An approved standard calculation method.

A performance‐based ‘Alternative Design’ which is a more comprehensive fire engineering design from first principles.

Figure 1.1 Typical hierarchical relationship for performance‐based design

Standard calculation methods are still being developed for widespread use, so compliance with performance‐based codes in most countries is usually achieved by simply meeting the requirements of the Acceptable Solution, with options 2 and 3 being used for special cases or very important buildings. Alternative Designs can sometimes be used to justify variations from the Acceptable Solution in order to provide improved safety, cost savings, or other benefits.

The code environment in New Zealand (described by Spearpoint, 2008), is similar to that in England, Australia and some Scandinavian countries. Moves towards performance‐based codes are being taken in the United States (SFPE, 2000). Codes are different around the world, but the objectives are similar; that is to protect life and property from the effects of fire (ABCB, 2005). It is not easy to produce or use performance‐based fire codes for many reasons; fire safety is part of a complex system of many interacting variables, there are so many possible strategies that it is not simple to assess performance in quantitative terms, and there is lack of information on behaviour of fires and the performance of people and buildings exposed to fires. A number of useful documents have been produced to assist users of performance‐based codes, including Custer and Meacham (1997), BS7974 (BSI, 2001), ABCB (2005), Spearpoint (2008) and ISO 23932 (2009). This book provides useful additional information, addressing the design of structures for fire safety, which is a small but important segment of the overall provision of fire safety.

1.3.2 Documentation and Quality Control

As the provision of fire safety in buildings moves away from blind adherence to prescriptive codes towards rational engineering which meets specified performance goals, the need for comprehensive documentation and quality control becomes increasingly important. It is recommended (ABCB, 2005; ISO, 2009) that quantitative calculations be put in context with a ‘qualitative design review’ which defines the objectives and acceptance criteria for the design, identifies potential hazards and fire scenarios, and reviews the overall design and fire safety features. The review and accompanying calculations should be included in a comprehensive report which describes the building and the complete fire design process (Caldwell et al., 1999). The report should address installation and maintenance of the fire protection features, and management of the building to ensure fire safety, with reference to drawings and documentation from other consultants.

It is important to consider quality control of fire safety throughout the design, construction and eventual use of the building, starting as early as possible in the planning process. Changes to the design often occur during construction, and these may affect fire safety if the significance of the original details is not well documented and well understood on the job site. The approving or checking authorities should also prepare a comprehensive report describing the design and the basis on which it is accepted or rejected. Those taking responsibility for design, approval and site inspection must be suitably qualified. The reliability of active and passive fire protection will depend on the quality of the construction, including workmanship and supervision.

1.3.3 Risk Assessment

Fire safety is all about risk. The probability of a serious fire in any building is low, but the possible consequences of such a fire are enormous. The objectives of design for fire safety are to provide an environment with an acceptably low probability of loss of life or property loss due to fire. Tools for quantitative risk assessment in fire safety are still in their infancy, so most fire engineering design is deterministic. The design methods in this book are deterministic, and must be applied with appropriate safety factors to ensure that they produce an acceptable level of safety.

Fire safety engineering is not a precise discipline, because any assessment of safety requires judgement as to how fire and smoke will behave in the event of an unplanned ignition, and how fire protection systems and the occupants of the building will respond. Design to provide fire safety is based on scenario analysis. For any scenario it is possible to calculate some responses, but the level of accuracy can only be as good as the design assumptions, the input data and the analytical methods available. Fire safety engineering is a very new discipline, so the precision of calculation methods will improve as the discipline matures, but it will always be necessary to exercise engineering judgement based on experience and logical thinking, using all the information that is available. Analysis of past fire disasters and visits to actual fires and fire damaged buildings are excellent ways of gaining experience.

1.4 Structural Fire Engineering

Traditional fire resistance has been simply achieved by designing buildings for room‐temperature conditions, then wrapping individual structural elements in protective insulation (for steel construction) or in sacrificial material (for concrete or timber construction). The primary reason for this approach is to limit temperatures in the interior of structural components, so that there is sufficient cold cross‐section to provide the required structural resistance in fire conditions.

The new discipline of structural fire engineering is leading to major advances in the provision of fire resistance, as an important component of overall building fire safety. Structural fire engineering is an amalgamation of the two older disciplines of structural engineering and fire engineering to ensure better prediction of building behaviour in the event of a fire, and better overall design for fire safety (Lennon, 2011).