Strength, durability and stability are the main criteria for material selection and design in the construction industry. Consequently, development and enhancement of construction materials is always an active and attractive field for engineers and researchers. Elevated temperature (fire) is a potential threat for any structural buildings that can cause a major damage. Response of construction materials exposed to elevated temperature or fire requires a full study and analysis with lessons learned from previous cases. In this paper, properties of the common construction materials such as concrete, steel and composite structures under high temperature events is presented and discussed. In addition, performance of advanced materials, such as Fiber Reinforced Polymer (FRP) and Concrete Filled Tubular (CFT) when exposed to high temperature was discussed. Recommendations from different design codes to increase fire resistance of structures are introduced. Finally, damage assessment of several bridges and buildings found in the literature exposed to fire events is summarized.
Construction Material; Fire Resistance; Impact of Fire on Structures; Structural Performance1. Introduction
Sustainability of structures is a main concern in the construction industry. Exposure to fire or elevated temperature is an extreme condition that leads to change in materials properties, consequently, change in overall behavior is expected. Many research efforts were devoted toward evaluation of materials’ performance when exposed to fire and high temperature events. These efforts provide understanding to the change of the materials properties and recommend guidelines to enhance preference in such events. Therefore, the objective of this paper is to highlight the differences in behavior of different construction materials when exposed to elevated temperature. In addition, design recommendations and codes requirements are emphasized to recognize these differences.
Structures exposed to high temperature events (fire) are usually investigated to evaluate their structure integrity and performance. Several active and passive fire protection approaches could be taken to minimize or control the impact of fire on structures and their components; however, the change of materials properties and the loss of structure stiffness require comprehensive evaluation of the structure’s performance to recommend the subsequent actions.
Three main categories: material properties, structural evaluation, and recommendations to increase fire resistance of structures and minimize the impact of high temperature events on structures are discussed in this paper.
2. Materials Properties
Material properties such as thermal expansion, density, and thermal conductivity need to be evaluated carefully to understand the change of the materials performance under extreme high temperature events. In addition, properties of materials’ constituents such as aggregates in case of concrete, affect the overall material behavior under high temperature events. The commonly used materials in the construction industry are discussed in the following subsections.
2.1. Concrete
Concrete during high temperature event has a complex behavior due to the differences in coefficient of thermal expansion of each constitution. Proportioning of concrete mixtures to achieve high strength and maintaining durability requirements during service live led to production of dense concrete mixtures with less water-cementitious material ratio (w/cm). Therefore, mechanical properties of HSC at elevated temperature are different from that of conventional concrete in two main areas: first, strength loss in the intermediate temperature range 100˚C to 400˚C and second the occurrence of explosive spalling of the HSC. Strength loss should be considered by incorporating the code and design specifications during the design stage. In addition, explosive spalling of the HSC and loss of the concrete cover during fire leads to direct exposure of the steel reinforcement to heat leading to loss of overall structural capacity [1,2]. Therefore, high strength concrete (HSC) and normal strength concrete (NSC) will have a significant difference in fire performance. Several factors that affect the fire resistance of concrete are concrete strength, moisture content, concrete density, and aggregate type [3,4].
Concrete Strength: Concrete with compressive strength higher than 55 MPa (8000 Psi) is more subjected to spalling than that of less compressive strength. Spalling of concrete usually happens during the initial stages of the fire due to the buildup of water pressure in the matrix or the effect of various thermal expansions in the matrix. HSC has very low permeability and water-cement ratio, consequently, moisture escapes with a slow rate and pore pressure will increase. This will lead to a major reduction in load bearing capacity and loss of concrete section during fire events is expected. Therefore, HSC could have a higher chance to spall more than NSC [3,4].
Moisture Content: Fire resistance of concrete is affected by the existence of free moisture or exposure to different levels of humidity (RH). Existence of free moisture depends on the nature of coarse aggregate and exposure to humidity. If the RH level exceeds 80%, major spalling may occur for the concrete element during fire. The ability of the free moisture to move from the side exposed to fire to the colder side reduces the internal pressure, hence, reduces the occurrence of spalling. In the case of HSC, the moisture movement is limited due to the high density, therefore, it is more susceptible to spalling [4,5].
Concrete Density: HSC has a dense paste, low watercement ratio, and other supplementary materials such as silica fume. In general, concrete with dense paste is prone to spalling when exposed to fire. During fire, the rate of transmission of the high temperature to the concrete core is high that leads to rapid loss of concrete surface layers (spalling) [3,4].
Type of Aggregate: 60% to 70% per volume of any concrete mixture is aggregate; therefore, change in the concrete proprieties is mainly affected by the type of coarse aggregates used in the mixture. Three types of aggregates are commonly used in the construction industry; carbonate, siliceous, and lightweight. Table 1 summarizes effect
ReferencesC. Castillo and A. J. Durrani, “Effect of Transient High Temperature on High-Strength Concrete,” ACI Materials Journal, Vol. 87, No 1, 1990, pp. 47-53.L. T. Phan, “Pore Pressure in High Strength Concrete at High Temperature,” Proceedings of the 3rd International Conference on Construction Materials: Performance, Innovations and Structural Implications, Vancouver, 2005.“Fire Safety of Concrete Buildings,” Cement Concrete & Aggregates Australia, 2010.V. Kodur, “Fire Performance of High-Strength Concrete Structural Members,” Institute for Research in Construction, Ottawa, 1999.D. R. Flynn, “Response of High Performance Concrete to Fire Conditions: Review of Thermal Property Data and Measurement,” Techniques Report NIST GCR 99-767.E. Ashley, “Fire Resistance of Concrete Structure,” Na tional Ready Mixed Concrete Association, 2007, pp. 67 70.
http://www.nrmca.org/research/FireResistance_CIF_Winter_07.pdfJ. A. Purkiss, “Fire Safety Engineering Design of Struc tures,” Butterworth-Heinemann, Jordon Hill, Oxford, 1996.D. N. Bilow and M. R. Kamara, “Fire and Concrete Struc tures,” Structures 2008: Crossing Borders, ASCE 2008.J. P. Rodrigues, L. Laím and A. M. Correia, “Behavior of Fiber Reinforced Concrete Columns in Fire,” Composite Structures, Vol. 92, No. 5, 2010, pp. 1263-1268.
doi:10.1016/j.compstruct.2009.10.029T. Kasper, C. Edvardsen, G. Wittneben and D. Neumann, “Lining Design for the District Heating Tunnel in Co penhagen with Steel Fiber Reinforced Concrete Seg ments,” Tunneling and Underground Space Technology, Vol. 23, No. 5, 2008, pp. 574-587.
doi:10.1016/j.tust.2007.11.001S. Somayaji, “Civil Engineering Materials,” 2nd Edition, Prentice Hall, 2001.R. G. Zalosh, “Industrial Fire Protection Engineering,” Wiley, Hoboken, 2003.R. H. Haddad, R. J. Al-Saleh and N. M. Al-Akhras, “Ef fect of Elevated Temperature on Bond between Steel Re inforcement and Fiber Reinforced Concrete,” Fire Safety Journal, Vol. 43, No. 5, 2008. pp. 334-343.
doi:10.1016/j.firesaf.2007.11.002Eurocode 2, “Design of Concrete Structures: Part 1.2: General Rules—Structural Fire Design,” European Committee for Standardization, Brussels, BS EN 1992-1-2, 2004.A. Y. Elghazouli, B. A. Izzuddin and K. A. Cashell, “Ex perimental Evaluation of the Mechanical Properties of Steel Reinforcement at Elevated Temperature,” Fire Safety Journal, Vol. 44, No. 6, 2009, pp. 909-919.
doi:10.1016/j.firesaf.2009.05.004J. P. Rodrigues, L. Laím and A. M. Correia, “Behavior of Fiber Reinforced Concrete Columns in Fire,” Composite Structures, Vol. 92, No. 5, 2010. pp. 1263-1268.
doi:10.1016/j.compstruct.2009.10.029N. D. Kankanamge and M. Mahendran, “Mechanical Pro perties of Cold-Formed Steels at Elevated Temperatures,” Thin-Walled Structures, Vol. 49, No. 1, 2011. pp. 26-44.
doi:10.1016/j.tws.2010.08.004J. H. Lee, M. Mahendran and P. Makelainen, “Prediction of Mechanical Properties of Light Gauge Steels at Ele vated Temperatures,” Journal of Constructional Steel Re search, Vol. 59, No. 12, 2003, pp. 1517-1532.
doi:10.1016/S0143-974X(03)00087-7J. Chen and B. Young, “Experimental Investigation of Cold-Formed Steel Material at Elevated Temperature,” Thin-Walled Structures, Vol. 45, No. 1, 2007, pp. 96-110.
doi:10.1016/j.tws.2006.11.003Y. C. Wang, P. M. H. Wong and V. Kodur, “An Experi mental Study of the Mechanical Properties of Fiber Rein forced Polymer (FRP) and Steel Reinforcing Bars at Ele vated Temperatures,” Composite Structures, Vol. 80, No. 1, 2007, pp. 131-140.
doi:10.1016/j.compstruct.2006.04.069A. Abbasi and P. Hogg, “Temperature and Environmental Effects on Glass Fiber Rebar: Modulus, Strength and In terfacial Bond Strength with Concrete,” Composites: Part B, Vol. 36, No. 5, 2005, pp. 394-404.
doi:10.1016/j.compositesb.2005.01.006A. Espinos, L. Gardner, M. L. Romero and A. Hospitaler, “Fire Behavior of Concrete Filled Elliptical Steel Col umns,” Thin-Walled Structures, Vol. 49, No. 2, 2011, pp. 239-255. doi:10.1016/j.tws.2010.10.008M. Yu, X. Zha, J. Ye and Y. Li, “Fire Responses and Resistance of Concrete-Filled Steel Tubular Frame Struc tures,” International Journal of Structural Stability and Dynamics, Vol. 10, No. 2, 2009, pp. 253-271.V. Moliner, A. Espinos, M. Romero and A. Hospitaler, “Fire Behavior of Eccentrically Loaded Slender High Strength Concrete-Filled Tubular Columns,” Journal of Constructional Steel Research, Vol. 83, 2013, pp. 137 146. doi:10.1016/j.jcsr.2013.01.011Q.-H. Tan, L.-H. Han and H.-X. Yu, “Fire Performance of Concrete Filled Steel Tubular (CFST) Column to RC Beam Joints,” Fire Safety Journal, Vol. 51, 2012, pp. 68 84. doi:10.1016/j.firesaf.2012.03.002A. Espinos, M. L. Romero and A. Hospitaler, “Advanced Model for Predicting the Fire Response of Concrete Filled Tubular Columns,” Journal of Constructional Steel Research, Vol. 66, No. 8-9, 2010, pp. 1030-1046.
doi:10.1016/j.jcsr.2010.03.002Z. Ma and P. Makelainen, “Behaviour of Composite Slim Floor Structures in Fire,” Journal of Structural Engineer ing, Vol. 126, No. 7, 2000, pp. 830-837.
doi:10.1061/(ASCE)0733-9445(2000)126:7(830)Z. Huang, I. W. Burgess and R. J. Plank, “The Influence of Shear Connectors on the Behavior of Composite Steel Framed Buildings in Fire,” Journal of Constructional Steel Research, Vol. 51, No. 3, 1999, pp. 219-237.
doi:10.1016/S0143-974X(99)00028-0F. Wald, L. Simoes da Silva, D. Moorec, T. Lennon, M. Chladna, A. Santiago, M. Benes and L. Borges, “Experi mental Behavior of a Steel Structure under Natural Fire,” Fire Safety Journal, Vol. 41, 2006, pp. 509-522.
doi:10.1016/j.firesaf.2006.05.006T. Hozjan, M. Saje, I. Planinc, S. Srpcic and S. Bratina, “Behavior of a Composite Concrete Trapezoidal Steel Plate Slab in Fire,” Open Journal of Civil Engineering, 2010.L. C. Leston-Jones, “The Influence of Semi-Rigid Con nections on the Performance of Steel Framed Structures in Fire,” Ph.D. Dissertation, University of Sheffield, 1997.ACI 216.1-07/TMS-0216-07, “Code Requirements for Determining Fire Resistance of Concrete and Masonry Construction Assemblies,” American Concrete Institute, 2007.K. D. Hertz and L. S. Sorensen, “Test Method for Spall ing of Fire Exposed Concrete,” Fire Safety Journal, Vol. 40, No. 5, 2003, pp. 466-476.
doi:10.1016/j.firesaf.2005.04.001K. Yang, H. Lee and O. Chan, “Experimental Study of Fire-Resistant Steel H-Columns at Elevated Tempera ture,” Journal of Constructional Steel Research, Vol. 62, No. 6, 2006, pp. 544-553. doi:10.1016/j.jcsr.2005.09.008A. S. Usmani, J. M. Rotter, S. Lamont, A. M. Sanad and M. Gillie, “Fundamental Principles of Structural Behavior under Thermal Effects,” Fire Safety Journal, Vol. 36, No. 8, 2001, pp. 721-744.
doi:10.1016/S0379-7112(01)00037-6A. M. Sanad, J. M. Rotter, A. S. Usmani and M. A. Con nor, “Composite Beams in Large Buildings under Fire— Numerical Modeling and Structural Behavior,” Fire Safety Journal, Vol. 35, No. 3, 2000, pp. 165-188.
doi:10.1016/S0379-7112(00)00034-5International Code Council, “2009 International Building Code (IBC 2009),” Country Club Hills, 2009.ACI/TMS Standard, “Code Requirements for Determin ing Fire Resistance of Concrete and Masonry Construc tion Assemblies (ACI 216.1-07/TMS-0216-07),” Ameri can Concrete Institute, Farmington Hills, 2007.American Society of Civil Engineers, “Standard Calcula tion Methods for Structural Fire Protection (ASCE/SEI/ SFPE 29-05),” Reston, 2007.ASTM E119-10b, “Standard Test Methods for Fire Tests of Building Construction and Materials,” ASTM Interna tional, West Conshohocken, 2003. www.astm.orgL. R. Taerwe, “Fire Design of Concrete Structures Ac cording to the Eurocodes: A Review,” ACI SP-255-4, 2008.L. Twilt, “The New Eurocode on Fire Design of Steel Structures,” The International Seminar on Steel Struc tures in Fire, Shanghai, 1-3 November 2001.Eurocode-Resouces.com, 2011.
www.eurocode-resources.comENV 1993-1-2, “Eurocode 3: Design of Steel Structures,” Part 1-2: General Rules, Structural Fire Design, CEN, 2006.EN1994-1-2, “Eurocode 4: Design of Composite Steel and Concrete Structures,” 2005.C. Gutiérrez-Montesa, E. Sanmiguel-Rojasa, A. S. Kai serb and A. Viedmab, “Numerical Model and Validation Experiments of Atrium Enclosure Fire in a New Fire Test Facility,” Building and Environment, Vol. 43, No. 11, 2008, pp. 1912-1928. doi:10.1016/j.buildenv.2007.11.010V. K. R. Kodur and M. Dwaikat, “A Numerical Model for Predicting the Fire Resistance of Reinforced Concrete Beams,” Cement and Concrete Research, Vol. 30, No. 5, 2008, pp. 431-443.
doi:10.1016/j.cemconcomp.2007.08.012M. B. Dwaikat and V. K. R. Kodur, “A Numerical Ap proach for Modeling the Fire Induced Restraint Effects in Reinforced Concrete Beams,” Fire Safety Journal, Vol. 43, No. 11, 2008, pp. 291-307.
doi:10.1016/j.firesaf.2007.08.003V. K. R. Kodur and N. K. Raut, “Fire Resistance of Rein forced Concrete Columns—State-of-the-Art and Research Needs,” ACI SP-255-4, 2008.H. M. Ali, P. E. Senseny and R. L. Alpert, “Lateral Dis placement and Collapse of Single-Story Steel Frames in Uncontrolled Fire,” Engineering Structures, Vol. 26, No. 5, 2004, pp. 593-607.
doi:10.1016/j.engstruct.2003.12.007A. Y. Elghazouli and B. A. Izzuddin, “Analytical Assess ment of the Structural Performance of Composite Floors Subject to Compartment Fires,” Fire Safety Journal, Vol. 36, No. 8, 2001, pp. 769-793.
doi:10.1016/S0379-7112(01)00039-XG. P. Mallett, “State-of-the-Art Review-Repair of Con crete Bridges,” Thomas Telford, London, 1994.J. J. Beitiel and N. R. Iwankiw, “Historical Survey of Multi-Story Building Collapses Due to Fire,” FPE 3rd Quarter, 2005.L. Giuliani, C. Crosti and F. Gentili, “Vulnerability of Bridges to Fire,” Proceedings of the 6th International Conference on Bridge Maintenance, Safety and Manage ment, Stresa, 8-12 July 2012.J. Scheer, “Failed Bridges Case Studies and Consequen ces,” Ernts & Sohn, Berlin, 2010.