Acceptance Criteria for Unbonded Post-Tensioned Concrete Exposed to Travelling and Traditional Design Fires

  • Chloe Jeanneret
  • John GalesEmail author
  • Panagiotis Kotsovinos
  • Guillermo Rein


Modern architecture is striving for large open spaces, which has resulted in the development of design methodologies such as the Improved Travelling Fires Methodology (iTFM). This methodology is only applicable in large open spaces where flashover may not occur. This paper studies the effect of various design fires, including traditional uniform fires and for the first time iTFM on flat-plate unbonded post-tensioned (UPT) concrete, a structural system which allows long flooring spans (> 8 m). The predictions of a structural model of high temperature unbonded prestressing tendon relaxation that is available in the literature are compared for the first time with previously published fire experiments thus validating the model. A novel case study based on a real building was then analysed using the model to propose an acceptance criterion based on the longest tendon length where rupture and extreme stress relaxation is prevented. Two types of steel, fabricated according to BS 5896 and AS/NZ4672, were analysed for various unbonded lengths (between 8.15 m and 65.2 m). Emphasis is on the unique deformation mechanisms present when prestressing steel is heated locally. The relaxation model has been validated for negligible slab deflection, allowing for discussion on the difference between the impact of travelling and uniform fires on the design of UPT concrete. The tendon rupture and relaxation analysis have novelty in showing that slow moving fires are more onerous structurally than fast moving or uniform fires and therefore are important to consider when defining critical design thermal boundaries in a design context. Results also demonstrate that tendons in similar designs require consideration to be limited in unbonded length. The development of new acceptance criteria herein is the first step in producing a generalized criteria for better informed structural fire design of UPT concrete exposed to fire.


Travelling fires Post-tensioned Prestressing steel Concrete Fire 



The researchers thank Luke Bisby and Mohammad Heidari for the discussions pertaining to the herein topics. NSERC Canada is acknowledged for their financial support of Chloe Jeanneret through York University’s USRA programme and John Gales through the Discovery programme.


  1. 1.
    Stern-Gottfried J, Rein G (2012) Travelling fires for structural design—part II: design methodology. Fire Saf J 54:96–112CrossRefGoogle Scholar
  2. 2.
    Lamont L, Usmani A, Drysdale D (2001) Heat transfer analysis of the composite slab in the Cardington frame fire tests. Fire Saf J 36 (8):815–839CrossRefGoogle Scholar
  3. 3.
    Rackauskaite E, Kotsovinos P, Jeffers A, Rein G (2017) Structural analysis of multi-storey steel frames exposed to travelling fires and traditional design fires. Eng Struct 150:271–287CrossRefGoogle Scholar
  4. 4.
    Rackauskaite E, Hamel C, Law A, Rein G (2015) Improved formulation of travelling fires and application to concrete and steel structures. Structures 3:250–260CrossRefGoogle Scholar
  5. 5.
    Law A, Stern-Gottfried J, Gillie M, Rein G (2011) The influence of travelling fires on a concrete frame. Eng Struct 33:1635–1642CrossRefGoogle Scholar
  6. 6.
    Gales J, Hartin K, Bisby L (2016) Structural fire performance of contemporary post-tensioned concrete construction. Springer Briefs in Fire, pp 91Google Scholar
  7. 7.
    Smith M, Gales J (2018) Connection behaviour in contemporary canadian buildings subjected to real fires. In: SFPE performance based design conference, pp 6Google Scholar
  8. 8.
    British Standards Institution (2019) PD 7974-1: application of fire safety engineering principles to the design of buildings Part 1: Initiation and development of fire within the enclosure of originGoogle Scholar
  9. 9.
    British Standard Institution (2019) PD 7974-3: application of fire safety engineering principles to the design of building Part 3: Structural response to fire and fire spread beyond the enclosure of originGoogle Scholar
  10. 10.
    Clifton CG (1996) Fire models for large firecells. HERA Report R4-83Google Scholar
  11. 11.
    Stern-Gottfried J, Rein G (2012) Travelling fires for structural design—part I: literature review. Fire Saf J 54:74–85CrossRefGoogle Scholar
  12. 12.
    Rein G, Zhang X, Torero L, Williams P, Heise A, Jowsey A, Lane B (2007) Multi-storey fire analysis for high-rise buildings. In: The 11th international interflam conferenceGoogle Scholar
  13. 13.
    Dai X, Welch S, Usmani A (2017) A critical review of “travelling fire” scenarios for performance-based structural engineering. Fire Saf J 91:568-578. CrossRefGoogle Scholar
  14. 14.
    Heidari M, Kotsovinos P, Rein G (2019) Flame extension and the near field under the ceiling for travelling fires inside large compartments. Fire and Materials Journal.Google Scholar
  15. 15.
    Khoury G (2000) Effect of fire on concrete and concrete structures. Prog Struct Mat Eng 2(4):429-447CrossRefGoogle Scholar
  16. 16.
    Dotreppe J-C, Franssen J-M, Bruls A, Baus R, Vandevelde P, Minne R, Van Nieuwenburg D, Lambotte H (1997) Experimental research on the determination of the main parameters affecting the behaviour of reinforced concrete columns under fire conditions. Mag Concr Res 49(179):117–127CrossRefGoogle Scholar
  17. 17.
    Lim LCS (2000) Stability of precast concrete tilt panels in fire. University of Canterbury, CanterburyGoogle Scholar
  18. 18.
    Kodur VKR, Dwaikat M (2008) A numerical model for predicting the fire resistance of reinforced concrete beams. Cement Concr Compos 30(5):431–443CrossRefGoogle Scholar
  19. 19.
    Gernay T, Millard A, Franssen J-M (2013) A multiaxial constitutive model for concrete in the fire situation: theoretical formulation. Int J Solids Struct 50(22–23):3659–3673CrossRefGoogle Scholar
  20. 20.
    Molkens T, Gernay T, Caspeele R, Nigro E, Bilotta A (2017) Fire resistance of concrete slabs acting in compressive membrane action. IFireSs 2017, 2017Google Scholar
  21. 21.
    Bailey CG, Ellobody E (2009) Fire tests on unbonded post-tensioned one-way concrete slabs. Mag Concr Res 61(1):67–76CrossRefGoogle Scholar
  22. 22.
    Gales J, Bisby L (2016) Insights into the complexity of structural fire response from repeated heating tests on post-tensioned concrete. In: Proceedings of the 9th international conference on structures in fire, New Jersey, pp 53–61Google Scholar
  23. 23.
    British Standards Institution (2008) Eurocode 2: design of concrete structures: British standard. BSi, LondonGoogle Scholar
  24. 24.
    Gales J, Bisby L (2014) Deformation and response of continuous and restrained post-tensioned concrete slabs at high temperatures. In: Proceedings of the 8th international conference on structures in fire, Shanghai, pp 305–312Google Scholar
  25. 25.
    Gales J, Bisby L, Stratford T (2012) High temperature creep deformation and failure behaviour of prestressing steel. In: Proceedings of the 7th international conference on structures in fire, Zurich, pp 659–668Google Scholar
  26. 26.
    NIST (2015) International R&D roadmap for fire resistance of structures: summary of NIST/CIB workshop. NIST Special Publication 1188Google Scholar
  27. 27.
    LaMalva K, Jeffers A, Quiel S, Gales J et al (2017) Structural fire engineering: guide to SEI ASCE 16-7 Appendix E. 235 pp. AcceptedGoogle Scholar
  28. 28.
    Bergman TL, Incropera FP, DeWitt DP, Lavine AS (2011) Fundamentals of heat and mass transfer, 7th ed. Wiley, LondonGoogle Scholar
  29. 29.
    Gales J, Bisby L, Gillie M (2011) Unbonded post tensioned concrete slabs in fire—part II—modelling tendon response and the consequences of localized heating. J Struct Fire Eng 2(3):155–172CrossRefGoogle Scholar
  30. 30.
    Gales J, Robertson L, Bisby L (2016) Creep of prestressing steels in fire. Fire Mater 40:875–895Google Scholar
  31. 31.
    Hamd R, Gillie M, Warren H, Stratford T, Wang Y (2018) The effect of load-induced thermal strain on flat slab behaviour at elevated temperatures. Fire Saf J 97:12–18CrossRefGoogle Scholar
  32. 32.
    British Standard Institution (2019) PD 6688-1-2: background paper to the UK National Annex to BS EN 1991-1-2Google Scholar
  33. 33.
    Lamont S, Usmani AS, Gillie M (2004) Behaviour of a small composite steel frame structure in a “long-cool” and a “short-hot” fire. Fire Saf J 39:327–357Google Scholar
  34. 34.
    Roberston L, Gales J (2016) Post-fire guidance for the critical temperature of prestressing steel. In: Interflam 2016: 14th international conference and exhibition on fire science and engineering. Royal Holloway College, Windsor, pp 1027–1037Google Scholar
  35. 35.
    IBC (2012). International building code. Country Farm Hills, Il., USA: International Code CouncilGoogle Scholar
  36. 36.
    Bailey CG, Khoury G (2011) Performance of concrete structures in fire. MPA. The Concrete Centre, UKGoogle Scholar
  37. 37.
    Gales J, Bisby L, MacDougall C, MacLean K (2009) Transient high-temperature stress relaxation of prestressing tendons in unbonded construction. Fire Saf J 44(4):570–579CrossRefGoogle Scholar
  38. 38.
    Fletcher IA (2010) Tall concrete buildings subjected to vertically moving fires: a case study approach. The University of Edinburgh, EdinburghGoogle Scholar
  39. 39.
    Law A (2010) The assessment and response of concrete structures subject to fire. The University of Edingburgh, EdingburghGoogle Scholar
  40. 40.
    Ellobody E, Bailey CG (2011) Structural performance of a post-tensioned concrete floor during horizontally travelling fires. Eng Struct 33:1908–1917CrossRefGoogle Scholar
  41. 41.
    Horová K, Jána T, Wald F (2013) Temperature heterogeneity during travelling fire on experimental building. Adv Eng Softw 62–63:119–130CrossRefGoogle Scholar
  42. 42.
    McAllister TP, Gross JL, Sadek F, Kirkpatrick S, MacNeill RA, Zarghamee M, Erbay OO, Sarawit AT (2013) Structural response of world trade center buildings 1, 2 and 7 to impact and fire damage. Fire Technol 49:709–739CrossRefGoogle Scholar
  43. 43.
    Kotsovinos P (2013) Analysis of the structural response of tall buildings under multifloor and travelling fires. The University of Edinburgh, EdinburghGoogle Scholar
  44. 44.
    Rush D, Lange D, Maclean J, Rackauskaite E (2016) Modelling the thermal and structural performance of a concrete column exposed to a travelling fire—Tisova fire test. In: Proceedings of the 9th international conference on structures in fire, pp 110–118Google Scholar
  45. 45.
    Rackauskaite E, Fernandez-Anez N, Bonner M et al. (2018) x-ONE fire experiment in a very large and open-plan compartment. In: The 12th international performance-based codes and fires safety design methodsGoogle Scholar

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© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of Civil EngineeringYork UniversityTorontoCanada
  2. 2.ARUPManchesterUK
  3. 3.Department of Mechanical EngineeringImperial CollegeLondonUK

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