تأثير الحرارة العالية على العارضات الخرسانية المسلحة المحسنة

This research examined the effect of high temperatures on reinforced concrete beams made from the groundworks of Hassia region in Syria. Concrete received additions of silica ash and plasticizers. Concrete cubic samples were then prepared with dimensions (15*15*15 cm), and samples for beams with simple support on both sides, with fixed dimensions for all samples of (b*h* L = 18*25*150 cm, respectively), and with a covering thickness of 3 cm. These samples were heated at the age of 28 days to different temperatures in all aspects using an electric oven, which was specially manufactured for this research. Samples were then cooled according to two cooling methods. The first is rapid cooling with water, and the second is a slow cooling with air. Then, necessary laboratory experiments were performed on these samples to measure the percentage of change in resistance, and the change of the torque resistance value in the samples of beams. The samples of beams were modeled and studied according to the finite element method, using the ABAQUS program. The results were read and compared with the experimental results. The results showed a decrease in the value of the resistive torque for the samples of beams with an increase in the heating temperature. The value of this decrease reached about 70% of the value of the resistive torque at the normal temperature. A difference in the value of this decrease is observed at the same temperature in accord with the used method of cooling. In air-cooled samples, it is greater than in water-cooled samples up to 750 °C. The decrease after this temperature in water-cooled samples becomes greater, noting the explosion of some samples heated up to 850 °C when cooled with water. Finally, the results and recommendations are indicated.