Fire Technology

, Volume 54, Issue 5, pp 1149–1169 | Cite as

Flush Endplate Connections in Fire: Time-Dependent Behavior of Tension Bolts

  • Ahmad H. El Ghor
  • Elie G. HantoucheEmail author
  • Mohammed Ali Morovat


Steel connections play a crucial role in maintaining the integrity and stability of steel building frames especially when exposed to fire temperatures. The behavior of flush endplate connections in fire is shown to be governed by tension bolt failure as bolts lose their strength and stiffness more rapidly at higher temperatures. As a result, the ability to predict the development of stresses in tension bolts of flush endplate connections at different stages of fire is of special importance. One of the factors influencing bolt stresses in fire is the thermal creep or time-dependent inelastic response of steel to elevated temperatures. Therefore, time- and temperature-dependent behavior of tension bolts of flush endplate connections in fire is the focus of this study. Stress-time histories in tension bolts are obtained by explicit consideration of thermal creep of steel in FE models of flush endplate connections at elevated temperatures. To better understand the effect of thermal creep on tension bolt behavior, the correlation between time-dependent rotational deformation of flush endplate connections and bolt stresses is also investigated. Further, the isochronous representation is utilized to study the rotational deformation and the tension bolt stresses under various applied moments ranging from 50% to 95% of the moment capacity and fire temperatures ranging from 450°C to 600°C with 25°C increment. Through such representation, it is indicated that the connection behavior is not only dependent on bolt strength degradation and applied moment, but also affected by the time duration of applied moments and temperatures. Also, with the inclusion of thermal creep of steel, the connection experiences higher rotation and excessive endplate deformation with stress relaxation leading to top tension bolt failure at earlier stages of fire. More specifically, for time exposure greater than or equal to 60 min, the failure temperature of the connection decreases from 600°C to around 550°C. Therefore, neglecting thermal creep of structural steel may result in an unsafe prediction of the overall response of flush endplate connections in fire.


Thermal creep Flush endplate Fire Isochronous curves Tension bolt stresses Connection rotation 



The authors gratefully acknowledge the financial support provided by the American University of Beirut Research Board under Grant No. 103371-23310, and by the Lebanese National Council for Scientific Research (LNCSR) under Grant No. 103091-22968. The authors further would like to thank researchers at the University of Sheffield for making the connection test results publicly available.


  1. 1.
    Li J-T, Li G-Q, Lou G-B, Chen L-Z (2012) Experimental investigation on flush end-plate bolted composite connection in fire. J Constr Steel Res 76:121–132CrossRefGoogle Scholar
  2. 2.
    Yu H, Burgess I, Davison J, Plank R (2011) Experimental and numerical investigations of the behavior of flush end plate connections at elevated temperatures. J Struct Eng 137:80–87CrossRefGoogle Scholar
  3. 3.
    Gao Y, Hongxia H, and Gang S (2013) Resistance of flush endplate connection under tension and shear in fire. J Constr Steel Res 86:195–205CrossRefGoogle Scholar
  4. 4.
    Al-Jabri K S, Seibib A, Karrech A (2006) Modelling of unstiffened flush end-plate bolted connections in fire. J Constr Steel Res 62:151–159CrossRefGoogle Scholar
  5. 5.
    Harmathy TZ (1967) A comprehensive creep model. J Basic Eng Trans ASME 89(3):496–502CrossRefGoogle Scholar
  6. 6.
    Harmathy TZ, Stanzak WW (1970) Elevated-temperature tensile and creep properties of some structural and prestressing steels. Fire Test Perform ASTM STP, 464:186–208CrossRefGoogle Scholar
  7. 7.
    Knight D, Skinner DH, Lay M G (1971) Prediction of isothermal creep. BHP Melbourne Research Laboratories, Report MRL 18/2, The Broken Hill Proprietary Company Limited Australia, pp 1–14Google Scholar
  8. 8.
    Skinner DH (1972) Determination of high temperature properties of steel. BHP Tech Bull 16(2): 10–21Google Scholar
  9. 9.
    [9] Fujimoto M, Furumura F, Ave T, Shinohara Y (1980) Primary creep of structural steel (SS 41) at high temperatures. Trans Archit Inst Jpn 296: 145–157CrossRefGoogle Scholar
  10. 10.
    Fujimoto M, Furumura F, Ave T (1981) Primary creep of structural steel (SM 50A) at high temperatures. Trans Archit Inst Jpn 306: 148–156CrossRefGoogle Scholar
  11. 11.
    Fujimoto M, Furumura F, Ave T (1982) Primary creep of structural steel (SM 58Q) at high temperatures. Trans Archit Inst Jpn 319: 147–155CrossRefGoogle Scholar
  12. 12.
    NIST (2005) Final report on the collapse of the world trade center towers. Report NIST NCSTAR 1, National Institute of Standards and Technology, Gaithersburg, MDGoogle Scholar
  13. 13.
    Luecke, WE (2005) Federal building and fire safety investigation of the world trade center disaster—mechanical properties of structural steels (draft). Gaithersburg, MD: Report NIST NCSTAR 1-3D, National Institute of Standards and TechnologyGoogle Scholar
  14. 14.
    Morovat MA, Lee J, Engelhardt MD, Helwig TA, Taleff EM (2011) Analysis of creep buckling of steel columns subjected to fire. Structures Congress, ASCE, pp 2929–2940Google Scholar
  15. 15.
    Morovat MA, Lee J, Engelhardt MD, Taleff EM, Helwig, TA, Segrest VA (2012) Creep properties of ASTM A992 steel at elevated temperatures. Adv Mater Res 446–449:786–792CrossRefGoogle Scholar
  16. 16.
    Huang ZF, Tan KH, Ting SK (2006) Heating rate and boundary restraint effects on fire resistance of steel columns with creep. Eng Struct 28: 805–817CrossRefGoogle Scholar
  17. 17.
    Li GQ, Zhang C (2012) Creep effect on buckling of axially restrained steel columns in real fires. J Constr Steel Res 71:182–188CrossRefGoogle Scholar
  18. 18.
    Kodur VKR, Dwaikat MMS (2010) Effect of high temperature creep on the fire response of restrained steel beams. Mater Struct 43:327–1341CrossRefGoogle Scholar
  19. 19.
    Li G-Q, Guo S-X (2008) Experimental on restrained steel beams subjected to heating and cooling. J Constr Steel Res 64:268–274CrossRefGoogle Scholar
  20. 20.
    Toric N, Harapin A, Boko I (2013) Experimental verification of a newly developed implicit creep model for steel structures exposed to fire. Eng Struct 57:116–124CrossRefGoogle Scholar
  21. 21.
    El Ghor AH, Hantouche EG, Morovat MA, Engelhardt MD (2016) Creep behavior of flush endplate connections at elevated temperatures due to fire. In: Structures in fire proceeding of the ninth international conference, Princeton University, New Jersey, USA, pp 435–442Google Scholar
  22. 22.
    El Ghor AH, Hantouche EG (2017) Thermal creep mechanical-based modeling for flush endplate connections in fire. J Constr Steel Res 136:11–23CrossRefGoogle Scholar
  23. 23.
    ABAQUS version 6.14 [Computer software]. Dassault systemes, Waltham, MAGoogle Scholar
  24. 24.
    Fields BA, Fields RJ (1989) Elevated temperature deformation of structural steel. Report NISTIR 88-3899, NIST, Gaithersburg, MDGoogle Scholar
  25. 25.
    Boresi, AP, Schmidt RJ (2003) Advanced mechanics of materials. Wiley, New YorkGoogle Scholar
  26. 26.
    Norton FH (1929) The creep of steel at high temperatures. McGraw-Hill Book Company, Inc, New YorkGoogle Scholar
  27. 27.
    Lee J, Morovat MA, Hu G, Engelhardt MD, Taleff EM (2013) Experimental investigation of mechanical properties of ASTM A992 steel at elevated temperatures. Eng J 50(4):249–272Google Scholar
  28. 28.
    Hu Y, Davison JB, Burgess IW, Plank RJ (2007) Comparative study of the behaviour of BS 4190 and BS EN ISO 4014 bolts in fire. In: Proceedings, ICSCS, Taylor & Francis, London, pp 587–592Google Scholar

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  • Ahmad H. El Ghor
    • 1
  • Elie G. Hantouche
    • 1
    Email author
  • Mohammed Ali Morovat
    • 2
  1. 1.Department of Civil and Environmental EngineeringAmerican University of BeirutBeirutLebanon
  2. 2.Ferguson Structural Engineering Laboratory, Department of Civil, Architectural and Environmental EngineeringThe University of Texas at AustinAustinUSA

Personalised recommendations