Numerical and Experiential Behavior of Hybrid R.C. Columns Under the Effect of Fire and Subjected to Eccentric or Concentric Load
摘要
The test results indicated that elevating the temperature to which the column was subjected had an adverse effect on both the characteristics of concrete and the properties of reinforcement bars, thereby leading to a reduction in the structural efficiency of the column. It took 45 min to burn the specimen at a temperature of 300 °C, while a specimen that burned at a temperature of 500 °C took a time of 2:30 h, and a specimen that burned at a temperature of 700 °C took a time of 6:15 h. The heat produced by a fire furnace has an apparent effect on all specimens, and this effect appears in a change of color of the concrete from a grey color to a light walnut color at 500 °C. At 700 °C, a light walnut color was appeared on all parts of the specimen, and sometimes a dark walnut color was appeared in specific locations of the specimen. Furthermore, the edges of the heated specimens become easily breakable by hand, whereas the unheated specimens can only be broken with a hammer. The test findings indicate that the load required to initiate the first crack lowers as temperature increases. Increased the concrete cover and changed the support type of unheated steel, fiber, and hybrid models from hinge-roller support to fixed-rolled supports, causing increased ultimate load capacity while increasing the slenderness ratio and the eccentricity ratio causing decreased ultimate load capacity. The ultimate load capacity rose by approximately 21.4%, 35.5%, and 38.2%, respectively, when the cover was increased to 30 mm, 40 mm, and 50 mm. The ultimate load capacity and first crack load were reduced by 77% and 88.5% compared to the same unheated fiber model under concentric load.