The behavior of cylindrical reinforced concrete structures subjected to lateral loading and high temperatures

Tubular cylinders of short and thin-walled Reinforced Concrete (RC) specimens were simulated in this study using the Nonlinear Finite Element Analysis (NLFEA) with a total of thirty-two models to investigate the effect of different parameters on their structural behavior. The investigated parameters during the parametric study stage were: (i) the height-to-diameter ratio. (H/D) of (0.5, 1.0, 1.5, 2.0, 3.0, 3.5, and 4.0), and (ii) the elevated temperature (T) of (23, 250, 500, and 750) °C. Specimens were simulated and analyzed as horizontal cantilever beams, and the NLFEA assisted in determining the behavior of closed concrete tubular walls in bending and shear. However, short specimens are defined as cylinders with (H/D) ratio less than 2.0 and carry more loading before the failure occurrence. In addition, high temperatures of more than 500 °C resulted in the maximum reduction in structural performance. Increasing the (H/D) ratio of more than 2.0 resulted in more ultimate loading capacity for specimens exposed to temperatures less than 500 °C. The shear cracking behavior of the closed tube cylinders is similar in all specimens, where an inclined crack appears first with an angle of approximately 45 degrees. Finally, the investigation results reveal that the reduction in H/D and exposed temperature (≤500 °C) degraded the overall structural behavior, including the cracking propagation process, ductility, and ultimate moment, while the ultimate load-carrying capacity was increased. The shear ultimate strength for the closed tubular RC thin-walled cylinders was predicted using a newly introduced simple mathematical expression when exposed to elevated temperatures.