منصة الرسائل والاطاريح: تحري سلوك وخواص البلاطات الخرسانية المسلحة المتعرضة الى لهب النار

الخلاصة

In the case of exposing a reinforced concrete structure to accidental fire, if this structure remains standing, an assessment of its residual capacity is needed . This study aims to reveal the effect of fire flame on the behavior of reinforced concrete slab specimens during and after exposure to fire. The experimental work includes casting and testing twenty four reinforced concrete slab specimens with dimensions of (600×600×40mm) divided into two series with target compressive strength of (30 and 38 MPa) designated as series A and B respectively .Each series was reinforced with two steel ratios of (0.00492 and 0.00875) . Sixteen reinforced concrete slab specimens were subjected to fire flame at the lower surface only to reach temperatures around of (400,500 and 600 °C) for one hour, then they were cooled gradually to room temperature. After that, they were tested in flexure to failure under uniformly distributed load .Control specimens of concrete(cubes, cylinders and prisms) and steel bars were subjected to the same environmental conditions that were subjected to the slab specimens to determine the changes in compressive strength ,modulus of flexural ,modulus of elasticity and splitting tensile strength of concrete and steel properties .These reinforced slab specimens were tested for weight loss, ultrasonic pulse velocity and rebound number before and after exposure to fire. Based on the results of this work, it can be concluded that the ultimate load capacity of the reinforced slab specimens decreased with the increase in fire temperatures. The higher decrease occurred in the slab specimens having higher steel ratio and subjected to 600 °C .The residual load capacity of reinforced slab specimens at 600 °C ranges between (84.2- 86%) for slab specimens of series (A) which were reinforced with steel ratios of (0.00875,0.00492) respectively and (83.7-85%) for slab specimens of series (B) with the same steel ratios. The fired slab specimens were found to be capable of resisting the service load but with a decreasing factor of safety. The non-destructive test results showed more reduction in the test results after exposure the slab specimens to fire compared with the control specimens. Results of the simplified approaches (Resheidat and Beeby methods) for the structural analysis of the reinforced concrete slab specimens subjected to fire flame , showed a good agreement with the experimental results, which conforms the validity of the analytical methods used to predict the structural behavior of the reinforced concrete slab specimens subjected to high temperatures.