Structural analysis of multi-storey steel frames exposed to travelling fires and traditional design fires

Abstract Most of the current understanding of building behaviour in fire is based on the adoption of the standard and parametric temperature-time fire curves. However, these design fires are based on small scale tests and idealize the thermal environment as uniform. Thus, they have important limitations on their applicability to large enclosures. Instead, in large open-plan compartments, travelling fires have been observed. To account for such fires, a design tool called Travelling Fires Methodology (TFM) has been developed and used for design. The aim of the present study is to compare computationally the structural response of a multi-storey steel frame subjected to both uniform design fires (available in current standards) and travelling fires. A two-dimensional 10-storey 5-bay steel frame designed according to ASCE 7-02 is modelled in the general finite element program LS-DYNA. Different fire exposures are investigated. They include travelling fires, Eurocode parametric curves, ISO-834 standard fire and the constant compartment temperature curve from the SFPE standard. These fires are applied to different floors, one at a time, to explore the influence on the structural response, resulting in a total of 80 different scenarios. The development of deflections, axial forces and bending moments is analysed. Uniform fires are found to result in approx. 15–55 kN (3–13%) higher compressive axial forces in beams compared to small travelling fires. However, the results show irregular oscillations in member utilization levels in the range of 2–38% for the smallest travelling fire sizes, which are not observed for any of the uniform fires. Peak beam mid-span deflections are similar for both travelling fires and uniform fires and depend mainly on the fire duration, but the locations in the frame and times when these peak displacements occur are different. The results indicate that travelling fires and uniform fires trigger substantially different structural responses which may be important in the structural design and selection of the critical members.

[1]  Yong Wang,et al.  A numerical study of large deflection behaviour of restrained steel beams at elevated temperatures , 2004 .

[2]  Hamid R. Ronagh,et al.  Structural response of a MRF exposed to travelling fire , 2015 .

[3]  Angus Law.  Perimeter Column Boundary Conditions in Structural Fire Modelling , 2016 .

[4]  B. R. Kirby.  Recent developments and applications in structural fire engineering design, a review , 1986 .

[5]  Guillermo Rein,et al.  Travelling fires for structural design-Part II: Design methodology , 2012 .

[6]  L. K. Tang,et al.  Advanced analysis for the assessment of steel frames in fire , 1998 .

[7]  Panagiotis Kotsovinos,et al.  Model parameter sensitivity and benchmarking of the explicit dynamic solver of LS-DYNA for structural analysis in case of fire , 2017 .

[8]  Ian Burgess,et al.  Analyses of the effects of cooling and fire spread on steel-framed buildings , 1996 .

[9]  Egle Rackauskaite.  iTFM : improved travelling fires methodology for structural design and the effects on steel framed buildings , 2017 .

[10]  R. L. Alpert.  Calculation of response time of ceiling-mounted fire detectors , 1972 .

[11]  Venkatesh Kodur,et al.  A performance based methodology for fire design of restrained steel beams , 2011 .

[12]  Fahim Sadek,et al.  An Experimental and Computational Study of Steel Moment Connections under a Column Removal Scenario | NIST , 2010 .

[13]  Jamie Stern-Gottfried,et al.  A Risk Based Framework for Time Equivalence and Fire Resistance , 2015 .

[14]  Guillermo Rein,et al.  The influence of travelling fires on a concrete frame , 2011 .

[15]  Martin Gillie,et al.  Structural behaviour during a vertically travelling fire , 2010 .

[16]  Eccs.  Recommendations for the fatigue design of steel structures , 1985 .

[17]  Panagiotis Kotsovinos,et al.  Analysis of the structural response of tall buildings under multifloor and travelling fires , 2013 .

[18]  Spencer E. Quiel,et al.  Plastic Axial Load and Moment Interaction Curves for Fire-Exposed Steel Sections with Thermal Gradients , 2008 .

[19]  Ehab Ellobody,et al.  Structural performance of a post-tensioned concrete floor during horizontally travelling fires , 2011 .

[20]  Ulf Wickström,et al.  Comments on calculation of temperature in fire-exposed bare steel structures in prEN 1993-1-2: Eurocode 3—design of steel structures—Part 1–2: general rules—structural fire design , 2005 .

[21]  Angus Law.  The Assessment and Response of Concrete Structures Subject to Fire , 2010 .

[22]  Darlene Rini,et al.  Recent Lessons Learned in Structural Fire Engineering for Composite Steel Structures , 2013 .

[23]  Guillermo Rein,et al.  Improved Formulation of Travelling Fires and Application to Concrete and Steel Structures , 2015 .

[24]  Asif Usmani,et al.  Behaviour of a small composite steel frame structure in a “long-cool” and a “short-hot” fire , 2004 .

[25]  D. A. Nethercot,et al.  Designer's guide to EN 1993-1-1 : Eurocode 3: Design of Steel Structures : General Rules and Rules for Buildings /L. Gardner and D. A. Nethercot , 2005 .

[26]  Panagiotis Kotsovinos,et al.  Engineering geometrically bi-linear columns to deliver fire resistance: Standard heating , 2015 .

[27]  Therese P. McAllister,et al.  Lateral torsional buckling of steel W-beams subjected to localized fires , 2013 .

[28]  Asif Usmani,et al.  Simulating the behavior of restrained steel beams to flame impingement from localized-fires , 2013 .

[29]  Andrew H. Buchanan,et al.  Structural Design for Fire Safety , 2001 .

[30]  S. Lamont,et al.  Fundamental principles of structural behaviour under thermal effects , 2001 .

[31]  Egle Rackauskaite,et al.  A Study on the Effect of Compartment Fires on the Behaviour of Multi-Storey Steel Framed Structures , 2015 .

[32]  Graeme Flint.  Fire induced collapse of tall buildings , 2005 .

[33]  Venkatesh Kodur,et al.  Response of steel beam–columns exposed to fire , 2009 .

[34]  Serdar Selamet,et al.  Symmetric and Asymmetric Collapse Mechanisms of a Multi-Story Steel Structure subjected to Gravity and Fire , 2013 .

[35]  Guillermo Rein,et al.  A Performance Based Methodology Using Travelling Fires for Structural Analysis , 2010 .

[36]  Guillermo Rein,et al.  Travelling fires for structural design-Part I: Literature review , 2012 .

[37]  Jean-Marc Franssen,et al.  Fire Design of Steel Structures: Eurocode 1-1-2: General Actions - Actions on Structures Exposed to Fire / Eurocode 3: Design of Steel Structures , 2016 .

[38]  Jean-Marc Franssen.  Improvement of the Parametric Fire of Eurocode 1 based on Experimental Tests Results , 2000 .