الفهرس 
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Abstract
This research was conducted to study the behavior of one-way reinforced concrete slabs subjected to fire and to investigate the fire risk after extinguishing To achieve this objective, sixteen simply supported one-way reinforced concrete s abs of span 3.0 m and thickness of 120 mm were considered. The aggregate used for the model was of siliceous type. The studied slabs used four concrete cover thicknesses namely; 15, 20, 25 and 30mm as well as two live load ratios namely 0.6 and 1.0. Also, the presence of 20 mm plaster thickness at the exposed surface for eight slabs was considered. The slabs were subjected to IS0834 standard fire, The investigation conducted by thermal analysis (heat transfer) and mechanical analysis. The thermal analysis was performed using finite difference method. The numerical and experimental data given by Lie and Williams- Leir (24) were used to verify the accuracy of the heat transfer model. The slab was designed according to the Egyptian code at ambient temperature with various concrete cover. The temperature distribution through concrete slab thickness obtained from the thermal analysis was used as an input to study the material properties at elevated temperatures. The temperature distribution was used to calculate the strength reduction in the steel and concrete according to Eurocode2-2004(30). The mechanical analysis was investigated to obtain the slab moment capacity degradation with temperature. This research was divided into two parts. The first phase used the standard fire without decay phase to calculate the fire resistance. However, the second phase used the parametric standard fire with decay phase to find the critical cooling time and consequently the maximum risk time. The importance of finding the maximum risk time is that such time is important for staying observant for possible impending failure after the start of the cooling phase.