Fire Technology

, Volume 53, Issue 3, pp 1333–1351 | Cite as

Anisotropic Curvature and Damage of Unbonded Post-tensioned Concrete Slabs During Fire Testing

  • Johan Sjöström
  • David Lange
  • Robert Jansson McNamee
  • Lars Boström


Two furnace tests, using two different fire exposures, on unbonded post-tensioned concrete slabs (1700 × 1200 mm) are reported. Local curvature is measured along two lines approximately in the middle of the slabs both parallel (longitudinal) and orthogonal (transverse) to the prestressing direction. More pronounced curvature in the transverse direction is accompanied by the formation of cracks running predominantly in the longitudinal direction. While the transverse curvature relaxes back to the original state after the cooling phase the curvature in the longitudinal direction ultimately exhibits upward deflection due to the hogging moment caused by the prestress in the tendons acting on a cross section with temperature reduced mechanical properties at the fire exposed side. The effect on crack formation due to the prestressing can additionally be detected by ultrasonic pulse velocity measurements in the different directions through the depth of the slab, where a reduction of 5–25% is observed in the transverse direction compared to the longitudinal direction. The phenomenological mechanical behaviour of the slabs is captured in a finite element model which describes the evolution of stress in the prestressing tendons. This model additionally suggests that the curvature in the transverse direction is independent of the prestressing in the longitudinal direction.


Concrete slab Fire Deflection Post-tension Standard fire curve Hydrocarbon fire curve Ultrasonic pulse velocity Crack formation 


  1. 1.
    Huang ZH, Burgess IW, Plank RJ (2003) Modeling membrane action of concrete slabs in composite buildings in fire. I: theoretical development. J Struct Eng– ASCE. 129(8): 1093–1102.CrossRefGoogle Scholar
  2. 2.
    Fédération Internationale du béton (2008) “Fire design of concrete structures—structural behaviour and assessment” State of the art report, Bulletin 46.Google Scholar
  3. 3.
    Hertz KD (2003) Limits of spalling of fire-exposed concrete. Fire Saf J 38(2): 103–116.CrossRefGoogle Scholar
  4. 4.
    Jansson R, Boström l (2013) Factors influencing fire spalling of self compacting concrete. Mater Struct 46(10): 1683–1694.CrossRefGoogle Scholar
  5. 5.
    Bailey CG, Ellobody E. (2009) Comparison of unbonded and bonded post-tensioned concrete slabs under fire conditions. Structural Engineer 87(19): 23–31.Google Scholar
  6. 6.
    Gales J, Hartin K, Bisby L.(2016) Structural fire performance of contemporary post-tensioned concrete construction. Springer, London.CrossRefGoogle Scholar
  7. 7.
    Kalifa P, Chene G, Galle C. (2001) High-temperature behaviour of HPC with polypropylene fibres - from spalling to microstructure Cem Concr Res 31(10): 1487–1499.CrossRefGoogle Scholar
  8. 8.
    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 of Struct Fire Eng 2(3): 155–171.CrossRefGoogle Scholar
  9. 9.
    Gales J, Parker T, Cree D, Green M, et al (2016) Fire performance of sustainable recycled concrete aggregates: mechanical properties at elevated temperatures and current research needs Fire Technol 52: 817–845.CrossRefGoogle Scholar
  10. 10.
    Zheng W, Hou X (2008) Experiment and analysis on the mechanical behaviour of PC simply supported slabs subjected to fire. Adv Struct Eng 11(1): 71–89.CrossRefGoogle Scholar
  11. 11.
    Bailey CG, Ellobody E.(2009) Fire tests on unbonded post-tensioned one-way concrete slabs. Mag Conc Res 61(1): 67–76.CrossRefGoogle Scholar
  12. 12.
    Yang JC, et al. (2015) International R&D Roadmap for Fire Resistance of Structures Summary of NIST/CIB Workshop, NIST Special Publication 1188, National Institute of Standards and Technology.Google Scholar
  13. 13.
    Ellobody E, Bailey C. G. (2008) Testing and modelling of bonded and unbonded post-tensioned concrete slabs in fire. Proceedings of the 5th International Conference on Structures in Fire (SiF’08), pp 392-405.Google Scholar
  14. 14.
    Ellobody E, Bailey CG, (2009) Modelling of unbonded post-tensioned concrete slabs under fire conditions. Fire Saf J 44(2): 159–167.CrossRefGoogle Scholar
  15. 15.
    Ellobody E, Bailey CG (2011) Structural performance of a post-tensioned concrete floor during horizontally travelling fires Eng Struct 33(6): 1908–1917.CrossRefGoogle Scholar
  16. 16.
    Stern-Gottfried J, Rein G (2012) Travelling fires for structural design-Part II: design methodology Fire Saf J 54: 96–112.CrossRefGoogle Scholar
  17. 17.
    Cooke GME (2001) Behaviour of precast concrete floor slabs exposed to standardised fires Fire Saf J 36(5): 459–475.CrossRefGoogle Scholar
  18. 18.
    Anderberg Y (1976) Fire-exposed hyperstatic concrete structures—an experimental and theoretical study PhD Thesis, Lund Institute of Technology, Lund.Google Scholar
  19. 19.
    Naik TR, Malhorta VM, Popovics al. (2004) The ultrasonic pulse velocity method. In: Malhorta VM, Carino NJ, (eds.) Handbook on nondestructive testing of concrete, 2nd edn. CRC Press, London.Google Scholar
  20. 20.
    Sjöström J, Jansson R, Lange D, Boström L et al (2012) Directional dependence of deflections and damages during fire tests of post-tensioned concrete slabs, Proceedings of the 7th International Conference on Structures in Fire, Zürich.Google Scholar
  21. 21.
    Lange D, Sjöström J, Jansson R, Boström L. (2012) Deflection of concrete floor slab during a fire test: tests and modelling, Proceedings of ICEM15, Porto.Google Scholar
  22. 22.
    Malhotra HL (1957) The effect of temperature on the compressive strength of concrete, Mag Concr Res 23: 1957.Google Scholar
  23. 23.
    Dassault Systémes Simulia Corp (2011) “ABAQUS 6.11.”.Google Scholar
  24. 24.
    Law A, (2010) The assessment and response of concrete structures subject to fire, PhD Thesis, The University of Edinburgh.Google Scholar
  25. 25.
    CEN, European Committee for Standardization (2002) EN 1991-1-2:2002 Eurocode 1: Actions on structures—Part 1-2: Actions on structures exposed to fire. Brussels.Google Scholar
  26. 26.
    CEN, European Committee for Standardization (2004) EN 1992-1-2:2004 Eurocode 2: Design of concrete structures—Part 1-2: General rules—Structural fire design. Brussels.Google Scholar
  27. 27.
    CEN, European Committee for Standardization (2005) EN 1993-1-2:2005 Eurocode 3: Design of steel structures—Part 1-2: Structural fire design. Brussels.Google Scholar

Copyright information

© Springer Science+Business Media New York 2016

Authors and Affiliations

  • Johan Sjöström
    • 1
  • David Lange
    • 1
  • Robert Jansson McNamee
    • 1
  • Lars Boström
    • 1
  1. 1.SP Technical Research Institute of SwedenBoråsSweden

Personalised recommendations