Fire Safety Engineering & Structures in Fire

1. Fire Safety Engineering & Structures in Fire History of Fire Safety Engineering Session JT1 Workshop at Indian Institute of Science 9-13 August, 2010 Bangalore India

2. Prescripción • Codes and standards are an attempt to achieve a minimum level of safety • They establish generalized rules that enable handling infrastructure in an homogeneous manner • They are not intended to solve individual problems

3. What buildings do Codes Describe? • How are these codes used? • Who is competent to use these codes? • Is there an alternative to codes & standards?

4. History • To understand the practise of Fire Safety Engineering it is essential to understand its history

5. Fire Safety Strategy • Main Concepts have not changed • Life Safety • Egress Strategy • Design of Egress paths • Detection and Alarm • Signalling • Structural Requirements • Compartmentation - deformations • Structural strength • Redundancy • Fire Suppression and control

6. The Origins • Regulations and Fire Service are born after the great fires of New York (1835), London (1861), Chicago (1871), Boston (1872) and San Francisco (1906). • Rules stem from the experience of fire fighters, architects and engineers • Very poor understanding of human behaviour, fire dynamics and structural behaviour

7. 1850-1940 • Building Separation Distances • Compartimentation • Size and separation of windows • Maximum Egress distances • Sprinklers • Passive fire protection – fire proofing • 1st Professional Fire Brigade – James Braidwood (1824)

8. Standard Fire (1906) • Compartment Fire (4 m x 4 m x 4 m) • Variable Ventilation & Fuel Load Structural Element Critical Temperature Rating

9. Aims • Worst Case Scenario • Curve is defined by an envelope to all fires • Rating is defined by total fuel consumption Increase of Fuel Load

10. Why the large safety factors? • Poor understanding of material behaviour at high temperatures • Poor understanding of fire dynamics • Poor fire fighting technology • Codes & Standards represent societies responsibility to guarantee safety – i.e. Large Safety Factors!

11. The Advantage of Codes & Standards • Codes and Standards gave structural engineers the freedom to build extraordinary buildings – Codes & standards represent an opportunity for innovation! • Structural engineers transformed cities!

12. 2nd World War • Great technological innovation in our understanding of “Fire” and its “Consequences” • BRE, NBS, Harvard, MIT, Tokyo, etc. • Codes & Standards take the lead over innovation in construction- codes & standards encourage innovation

13. When Codes are Ahead • Most buildings fall within the domain of Codes & Standards • To apply Codes & Standards it is necessary to understand them and have experience with them – an apprenticeship! • Engineering is subordinated to Codes & Standards

14. 1950-1970 • City density increases • Building complexity increases • Codes & standards fall behind!

15. Great Fires of the 1960’s • Problems with smoke management • Problems with materials selection • Structural problems • Complexity exceeds knowledge • Codes & standards generate a false sense of safety • Codes & standards become a barrier to innovation for an uncertain gain in safety

16. When Codes are Behind • Most buildings fall outside the range of applicability of codes & standards • Those who apply the codes & standards have to use them as a tool, understand their limitations, know when to depart from them and when to supplement them • Codes and standards are subordinated to engineering

17. The Answer • Understanding the Problem - America Burning, UK Building Fire Act, etc. • US$100’s of millions on research investments • NIST, FRS, CSIRO, NBR, VTT, SP, SINTEF, vfdb, CSTB, etc. • New methodologies for fire dynamics (zone models, empirical corelations, CFD models, etc.) • New material flammability screening methods (LIFT, cone calorimeter, etc.) • Deeper understanding of human behaviour in fire (egress models, etc.) • Higher Education programmes • We learn to calculate!

18. El Resultado • Recognition of our engineering competence • Codes evolve • Fire Safety Engineering appears as recognized profession • Performance Based Design

19. Structural Fire Engineering • The Ove Arup Philosophy enters Fire Safety Engineering – Codes & Engineering as a tool in communion with Architecture • Standard Fire – recognition of limitations and safety factors • Fire proofing is only “a” solution • Structural behaviour is part of a fire strategy – trade-offs & compensations • It is the “design” and not the “material”

20. Cardington -1990’s • Definition of space is more important than material selection

21. Reinforcement Temperature [oC] Failure (1 hour rating) 2 hr 3 hr Failure (3 hour rating) Time ↑ 1 hr 550 Failure (2 hour rating) TReinforcement 20 TGas Time [hours] Insulation Temperature [oC] Beam 1 hr 2 hr 3 hr TGas 550 TBeam 20 TGas Time [hours] Insulation The Structural Analysis (2000’s) • Detailed understanding of structural behaviour in fire • Steel vs Concrete • Error Bars vs Refined Calculations

22. Temperature [oC] Beam 1 hr 2 hr 3 hr TGas 550 TBeam 20 TGas Time [hours] Insulation Structural Analysis

23. Reinforcement Temperature [oC] Failure (1 hour rating) 2 hr 3 hr Failure (3 hour rating) Time ↑ 1 hr 550 Failure (2 hour rating) TReinforcement 20 TGas Time [hours] Insulation Structural Analysis

24. The Analysis of the Fire (2000’s) • The Standard Fire: Does not represent heat transfer to a structure – only a standardized screening method • Parametric T vs t curves only useful when analyzing small cubic compartments (4 m x 4 m x 4 m) – Require a correct heat transfer analysis • When do we need to do Computational Fluid Dynamics?

25. Codes & Standards (2000’s) • Limited to conventional infrastructure • Conventional is everyday less frequent • Innovation in Construction has advanced much faster than fire safety codes & standards (construction methods, size, complexity, technology, materials, etc.) • Innovation has advanced much faster than our capability to educate engineers to be able to use codes & standards as engineering tools • Codes & Standards still give us a “false” sense of safety, thus hamper investment in innovation – we still do not know what we do not know!

26. Investment in Knowledge – 1970’s Results • Codes, Standards & Engineering supporting Architectural Design • Novel Designs could be constructed • Beaubourg is to Fire Safety Engineering what the Sydney Opera House is to Structural Engineering • Demonstration of Performance – Quantifying Safety • Reduction of Uncertainty • Cost Reduction • Elimination of Unnecessary Protection – False sense of safety • Optimization

28. Where are we now? • Codes & Standards are a true obstacle to innovation • Not a criticism to the codes but to the lack of knowledge of those who use them • In the evolution cycle prescription is today subordinated to engineering • We need engineers not apprentices • We are not educating those engineers