The structural behavior and simplified thermal analysis of normal-strength and high-strength concrete beams under fire

• Published in: Engineering structures Vol. 33; no. 4; pp. 1123 - 1132
• Main Authors: Choi, E.G., Shin, Y.S.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-04-2011; Elsevier
• Subjects: Applied sciences; Beams (structural); Building structure; Building technical equipments; Buildings; Buildings. Public works; Compressive strength; Concretes; Construction (buildings and works); Cover thickness; Exact sciences and technology; Failure; Fire behavior of materials and structures; Fire protection; Fire test under loading; Fires; High strength concrete; High-temperature; Mathematical models; Reinforced concrete; Reinforced concrete structure; Spalling; Stresses. Safety; Structural analysis. Stresses; Temperature gradient; Thermal transfer analysis; Thermal transfer analysis; Spalling; Cover thickness; High-temperature; High strength concrete; Fire test under loading; Compressive strength; High temperature; Experimental study; Modeling; Beam(mechanics); Reinforced concrete; Experimental result; Failure analysis; Fire test; Concrete construction; Thermal analysis; Bursting; Heat transfer; Structural analysis
• ISSN: 0141-0296; 1873-7323
• DOI: 10.1016/j.engstruct.2010.12.030

The objective of this study is to investigate the effects of concrete compressive strength and cover thickness on the structural behavior of reinforced concrete (RC) beams under fire. For this purpose, four normal-strength and high-strength concrete test beams were fabricated and tested under the ISO 834 standard fire curve to point of the failure. The test set-up was designed to evaluate the heat distribution and displacement changes of simply supported beams subjected to sustained loads under fire. Test results for normal-strength and high-strength concrete beams were compared for each of the test variables. The test results show that the relationships between time and temperature distributions in the beam sections are very similar and are unrelated to the strength of the concrete, with the exception of the upper part of the beam section. They also showed that the rates of deflection increase for both normal-strength and high-strength concrete beams is very similar before spalling but becomes remarkably high for high-strength concrete beams after spalling. A simplified model was proposed to determine the effect of spalling on the temperature gradient of a high-strength concrete beam. The results of finite difference method (FDM) analysis using this proposed model showed a section temperature gradient that was similar to that of the test results.