Fire Performance of Reinforced Concrete Beams under Design Fire Exposure

To investigate the shear capacity of indirectly loaded reinforced concrete beams under and after fire exposure, load tests were conducted on eight full-scale specimens exposed to fire testing in a furnace chamber, and the effects of additional transverse reinforcement in the junction region between the primary and secondary beams on the shear capacity, fire resistance, failure modes and deflection were analysed. The results indicate that the slopes of the diagonal cracks in post-fire tested reinforced concrete beams without additional transverse reinforcement were shallower than those of a similar reference beam not exposed to fire, and that the ultimate capacities of reinforced concrete beams with additional transverse reinforcement decreased obviously after fire exposure. However, beams with additional transverse reinforcement exhibited increased fire resistance times and reduced strains in their reinforcement, indicating the benefit of conservatively providing such reinforcement. The findings of this study are expected to provide a reference for the improved fire-resistant design of indirectly loaded beams.

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A modified layered-section method for responses of fire-damaged reinforced concrete beams under static and blast loads

International Journal of Protective Structures ◽

10.1177/2041419616658384 ◽

2016 ◽

Vol 7 (4) ◽

pp. 495-517 ◽

Cited By ~ 7

Author(s):

Lu Pan ◽

Li Chen ◽

Qin Fang ◽

Chaochen Zhai ◽

Teng Pan

Keyword(s):

Reinforced Concrete ◽

Strain Rate ◽

Bearing Capacity ◽

Concrete Beams ◽

Blast Resistance ◽

Reinforced Concrete Beams ◽

Fire Exposure ◽

Strain Rate Effects ◽

Section Method ◽

Rate Effects

Reinforced concrete structures are currently under the threat of both fire and blast. The absence of theoretical methods demonstrates a drawback in the assessment of blast-resistant structures after exposure to fire. A modified layered-section method was developed in this article, which was not only able to determine the complete static resistance–deflection curves of fire-damaged reinforced concrete beams but also able to predict the responses of reinforced concrete beams subjected to blast after fire exposure. The high-temperature effects and the strain-rate effects were included in the concrete and steel material models in the proposed method. A corresponding calculation program FBBA was also compiled based on the explicit Newmark algorithm on the platform of Maple software. The developed method and program were validated by the existing test results. Analytical results showed that after fire exposure, the reinforced concrete beams show significant degradation in the residual bearing capacity, but increase in the ductility. The higher the steel reinforcement ratio, the more degradation the bearing capacity of reinforced concrete beams after fire exposure suffers. The blast resistance of the fired reinforced concrete beams was underestimated without considering the strain-rate effects or just considering the average strain-rate effects.

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