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Effect of Fire Flam on Properties of Plain and Reinforced Concrete Beams | ||
| journal of kerbala university | ||
| Article 1, Volume 5, Issue 3, 2009, Pages 167-183 PDF (0 K) | ||
| Author | ||
| Mahdi Saleh Essa | ||
| Abstract | ||
| In the present study, compressive strength, rate of free drying shrinkage of plane concrete and load-deflection behavior of reinforced concrete beam specimens under the effect of fire flame exposure are presented. Plain concrete (150mm) cube specimens and (100*100*500mm) prisms were subjected to fire flame temperatures ranging between (25-550 ºC) at different ages of 30 and 60 days. Two temperature levels of 400 ºC and 550 ºC were chosen with two different exposure durations of 0.5 and 1.0 hour. Cube compressive strength and rate of drying shrinkage were explored after fire flame exposure and compared with the control (unburned) specimens. Ten rectangular reinforced concrete beam specimens (100*150*1000mm) were cast and subjected to fire flame at temperature levels of 400 ºC and 550 ºC, with two periods of exposure 0.5 and 1.0 hour. These beam specimens were tested in flexure until failure after exposure to fire flame and the load – deflection relationship was recorded and compared with that of the control (unburned) beam specimens. Based on the results of this research, the compressive strength of concrete was affected adversely by fire flame and the degree of damage increases when the fire temperature and/or period of exposure were raised. For the fire temperatures and periods of exposure investigated, the residual compressive strength ranged between (70-78%) at 400 ºC and (59-65%) at 550 ºC burning temperature. It was found that the exposure to fire flames increases the rate and intensity of drying shrinkage of free concrete prisms. This increase was found to reach 50% if temperature of fire approaches 550 ºC. It was noticed that the load-deflection relationship of reinforced concrete beams exposed to fire flame is more leveled representing softer load-deflection behavior than that of the control beams. Also, it was found that both the ultimate resisted load and moment carrying capacity decrease remarkably after fire exposure. This can be attributed to the early cracking and lower modulus of elasticity. Also, it was found that the temperature distribution through the thickness of beam is identical for all the beams which have the same thickness | ||
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