Sponsors: CERIB. Dr. Guillermo Rein. Department of Mechanical Engineering

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2 Travelling Fires for Structural Design Sponsors: CERIB Dr. Guillermo Rein Department of Mechanical Engineering

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4 Across Disciplines Fire & Structures Fire Structures The interface between fire and structures is the intersection of the two sets

5 Lame Substitution of the 1st Kind Fire & Structures Fire Failure of structure at T = XºC When structural engineers are entirely replaced by pseudo-science. It survives in many standards.

6 Lame Substitution of the 2nd Kind Fire & Structures Structures When fire engineers are entirely replaced by pseudo-science. It is mainstream.

7 Lame Substitution of the 3 rd Kind Fire & Structures Failure of structures at T=XºC When both fire and structural engineers are simultaneously replaced by pseudo-science. Any similarity with reality is a mere coincidence.

8 Ancient Traditional Design Fires Standard Fire, 1880 (on paper since 1912) Swedish Curves, 1972 Eurocode Parametric Curves, 1995 Imposed assumption: Uniform burning and uniform temperature, just like inside a furnace.

9 Scale Matters Here be Fire Tests Blind extrapolation Over there be Real Buildings

10 Blind Extrapolation from Limited Experience Fire in Furnace Blind extrapolation Fire in Normal compartment Fire in Large compartment Fire in Multistorey building

11 Limitations For example, limitations according Eurocode: Floor areas < 500 m 2 Near rectangular enclosures Heights < 4 m No ceilings openings Moderate thermal-inertia of lining

12 < 500 m 2 floor? Rectangular? < 4 m high? Excel, London WTC Transit Hub

13 Insulating Lining? No Ceiling Opening? Arup/Peter Cook/VIEW Renzo Piano The Shard Arup Campus

14 Love the Architects: Design Is out of Bounds We surveyed 3,000 compartments, most of the campus of King s Buildings at the University of Edinburgh. Buildings : 66% of volume within limitations Buildings from 2000: 8% of volume within limitations Modern architecture increasingly produces buildings whose fire behaviour falls outside our field of knowledge Jonsdottir et al, Out of range, Fire Risk Management 2009

15 The Titanic complied with all codes. Lawyers can make any device legal, only engineers can make them safe" Prof VM Brannigan University of Maryland

16 WHY TFM? Fires have been observed to travel across a floor plate burning over a limited area Non-uniform temperature distributions Long fire durations (up to 20 h Meridian Plaza) World Trade Centre, New York (2001) Windsor Tower, Madrid (2005) Faculty of Architecture, TU Delft (2008) Interstate Bank, Los Angeles (1988) One Meridian Plaza, Philadelphia (1991)

17 Fire Spread Large Floor A Amax Amax * Ignite Spread Travel area of the fire increasing with time

18 Travelling Fires Methodology

19 Fire Scenarios Travelling fires Eurocode parametric curves

20 Heat Transfer, T g -> T s STEEL TFM CONCRETE

21 Structural Results Rebar Temperature 500 Rebar Temperature ( C) % 5% 10% 25% 50% 100% Time (h) Law et al, Engineering Structures 2011

22 Family of Fires Not Just One Fire Cast in Stone range of sizes <=> range of spread rates Rebar Temperature

23 Location of Peak Temperature

24 Comparison to Traditional Methods (steel + 60 min fire protection)

25 Conclusions In large compartments, post-flashover fire cannot occur, but a travelling fire would develop. 1. TFM is a novel framework complementing traditional methods 2. TFM can produce more onerous conditions for the structure. 3. TFM triggers previously unnoticed structural mechanisms. 4. Among the fastest knowledge-transfer case from research to industry in FSE. ARUP

26 4 Pancras Square Battersea View 58 The Scalpel Two New Ludgate Nova Victoria 39 iconic buildings in UK S2 King s Cross Barlett, UCL One New Ludgate Kings House Sponsors: CERIB

27 Refined TFM Fire Sizes Reference Details LL ff,mmmmmm/mmmmmm = ss mmmmmm/mmmmmm tt bb Spread rates (mm/s) [1] Wood cribs in the open [2] Lateral or downward spread on thick solids 1 [3] Tests on natural fires in large scale compartments [4] Reconstruction of WTC fires (2001) [5,6] First Interstate Bank Fire (1988) 14.5 [1] Thomas PH. Some Aspects of the Growth and Spread of Fire in the Open. Forestry 1967;40: [2] Quintiere JG. Principles of Fire Behaviour. Cengage Learning; [3] Kirby BR et al. Natural fires in large scale compartments - A British Steel technical, Fire Research Station collaborative project [4] Gann RG et al. Reconstruction of the Fires and Thermal Environment in World Trade Center Buildings 1, 2, and 7. Fire Technol 2013;49: [5] Nelson HE. An Engineering view of the fire of may 4, 1988 in the First Interstate Bank building Los Angeles, California [6] Routley JG. Interstate Bank Building Fire. Los Angeles: 1988.

28 Travelling Fires Each structural element sees a transient combination of Near Field and Far Field temperatures as the fire travels short & hot ~ 900 to 1200 C for 20 min long & cold ~ C for hours Stern-Gottfried and Rein, Fire Safety Journal, 2012

29 ss spread rate, tt time, ll fire area (%), WW compartment width, HH ceiling height, QQ " - fuel load density Far Field Smoke long and cool TT ffff xx, tt = TT HH LL ll tt WW QQ " xx LL ll tt xx ll tt L xx ll tt for xx ll LL xx ll tt = ss tt; ll tt = min ll, ss tt LL ; for xx ll > LL x l t = L; l t = 1 + L f s t L.

30 Refined TFM Near Field Flames short and hot

31 Refined TFM Near Field Flames short and hot Integration of average of near field + far field Effective nearfield temperature

32 A Case Study Flame Flapping Steel beam: a - unprotected b - 60min protection c - 120min protection Concrete rebar: d m cover e m cover ll

33 Refined TFM Fire Sizes Fire length - Lf (m) Heat release rate - Q" (kw/m 2 )

34 Refined TFM Far Field Smoke long and cool Alpert s equation: TT mmmmmm TT = QQ rr HH

35 Effective Near-Field TT ff = TT + TT nnnn 2rr xx1 + dd 2TT rr xx2 ff QQ 2 3 HH ff ff rr xx2 where rr 2 = ff 2 rr xx2 = mmmmmm LL ff 2, rr 0 rr xx1 = max 0, rr 0 LL ff 2 ; TT nnnn = 1200 rr 0 = HH TT nnnn TT

36 Location of Peak Temperature

37 25% travelling fire: EC long-cool parametric fire: 20 min 40 min 60 min 85 min Effect of Fire Scenario

38 Response of 10-Storey Frame Numerical tested: 10-storey steel frame designed by NIST FEM simulations in LS-DYNA with Hughes-Liu beam elements (after successful benchmarking) Failure criteria based on section capacity (buckling and bending) 60 fire scenarios : travelling fires vs. simultaneous long-cool parametric fire (EC) Analysis of the evolution of deflections, axial forces and bending moments in the frame. 60 min 120 min 180 min 191 min displacement scale factor 5

39 Oscillations of Axial Forces and Bending Reversal of Axial Forces Bay symmetry for EC: 1 & 2 = 4 & 5

40 Quicker Development of Displacements

41 Travelling Fires Methodology

42 Travelling Fires Methodology

43 Travelling Fires Methodology

44 Travelling Fires Methodology