Title: Restraint mechanisms in precast concrete double-tee floor systems subjected to fire
Date: Summer, 2013
Page number: 95-110
Author(s): Nader M. Okasha, Stephen Pessiki
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This paper examines restraint mechanisms in precast, prestressed concrete structures under fire loading. The focus of the study is a prototype precast, prestressed double-tee beam typically used for precast concrete
parking structures. The study examines idealized (simple and fixed) single-span restraints and three realistic restraint mechanisms:
• multiple-span successive spans
• gravity support elements (for example, spandrels or inverted-tee girders)
• flange connectors
The analytical approach included nonlinear heat transfer analysis of temperatures throughout a double tee at different fire durations and nonlinear structural analyses of restraint forces and flexural strengths. The strengths were found to vary significantly with boundary condition and fire duration. The strength is significantly less when only the flange is restrained compared with when only the web is restrained and when the entire cross section is restrained. The flexural strength of a beam restrained by spandrels or inverted-tee girders is only slightly greater than that of a simply supported beam. Finally, the strength of a beam restrained by any practical number of flange connectors is only slightly higher than that of a simply supported double-tee beam.
1. Gustaferro, A. H., and L. D. Martin. 1989. Design for Fire Resistance of Precast Prestressed Concrete. MNL-124-89. 2nd ed. Chicago, IL: PCI.
2. Okasha, N. M. 2007. “Analytical Evaluation of Restraint Mechanisms in Precast Concrete Double Tee Floor Systems Subjected to Fire Loading.” MS thesis, Department of Civil and Environmental Engineering, Lehigh University, Bethlehem, PA.
3. Okasha, N. M., and S. Pessiki. 2006. “Analytical Evaluation of Restraint Mechanisms in Precast Concrete Double Tee Floor Systems Subjected to Fire Loading.” ATLSS report 06-24, Lehigh University, Bethlehem, PA.
4. ASTM (American Society for Testing and Materials) E119. 2005. Standard Test Methods for Fire Tests of Building Construction and Materials. West Conshohocken, PA: ASTM.
5. ISO 834-2. 2009. Fire-Resistance Tests - Elements of Building Construction Part 2: Guidance on Measuring Uniformity of Furnace Exposure on Test Samples. Geneva, Switzerland: International Organization for Standardization.
6. Lie, T. T. 1992. Structural Fire Protection. Manualsand Articles on Engineering Practice, no. 78. New York, NY: American Society of Civil Engineers.7. Eurocode 2 ENV 1992-1-2. 1996. “Part 1.2, General Rules-Structural Fire Design.” In Design of Concrete Structures. Brussels, Belgium: European Committee for Standardization.
8. Thompson, J. M. 2004. “Behavior and Design of Precast Prestressed Concrete Inverted Tee Girders with Multiple Web Openings for Service Systems.” PhD diss., Department of Civil and Environmental Engineering, Lehigh University, Bethlehem, PA.
9. PCI. 2004. PCI Design Handbook: Precast and Prestressed Concrete. MNL-120. 6th ed. Chicago, IL: PCI.
10. ACI (American Concrete Institute) 318. 2005. Building Code Requirements for Structural Concrete (ACI 318-05) and Commentary (ACI 318R-05). Farmington Hills, MI: ACI.
11. Oliva, M. G., J. A. Pincheira, and F. I. Kusumo-Richard. 1998. Test on Double Tee Beam Flange Connectors Subjected to Monotonic and Cyclic Loading. PCI Journal 43 (3): 82–96.
12. Shaikh, A. F., and E. P. Feile. 2002. “Testing of JVI Vector Connector.” University of Wisconsin-Milwaukee, WI.