الفهرس 
Analysis of non-prismatic reinforced concrete beamsOnly 14 pages are availabe for public view
 |  | from | 341 |  |  |
| | | from | 341 | | |
Abstract
Non-prismatic reinforced concrete beams with recesses have challenging issues in their analysis owing to the developed discontinuity regions (Dregions)due to the abrupt change in the beams’ depth. Thus, stresses concentration is developed at the recesses’ corners, which may result in a premature failure due to improper detailing for such regions. The main purpose of this study is to investigate the effect of providing recesses on the structural behavior of reinforced concrete beams. Consequently, the present study provides an experimental investigation on nine non-prismatic reinforced self-compacting concrete beams with a recess in both compression and tension sides of the beams, tested under the effect of repeated loading. The test variables included the recess location, recess size, and the reinforcement configuration around the tensile recess. Besides, proposed strut-and-tie models(STMs) for all tested beams have been developed based on the cracking patterns and principle stresses contours obtained from elastic finite element analysis in order to present the load transfer mechanism for those beams. The obtained results from STMs are compared with the experimental results. The comparison revealed that the STM gave good predictions with an average of about 0.84 of the ultimate experimental value and a coefficient of variation of about 6%. In addition, a parametric study on twenty-one beams with recesses has been conducted on the governing parameters of the recess in order to investigate the effect of providing recesses on the ultimate capacity and calculate the stress concentration factor (SCF) due to providing a recess in either a compression or a tension zone, as well as calculating the reinforcement stress jump due to cracking at a tensile recesses’ corners. It was found that the most significant parameter was the recess depth from the viewpoint of ultimate capacity and stress concentration factor. For tensile recesses ’depths ranged from 0.125 to 0.625 of the overall beam’s depth, the stress concentration factors ranged from 1.76 to 5.13. It could be concluded that increasing the curtailed longitudinal reinforcement length from development length to development length plus one and half times of the tensile recess’s depth resulted in decreasing the reinforcement stresses jump by about 29% to 40% for the tensile recesses ’depths ranged from 0.25 to 0.50, respectively. It could also be concluded that the best location for providing a recess is in the shear span zone from the viewpoint of predicted ultimate capacity and stress concentration factor on condition the depth of recesses should be limited to about 30% of the beam’s total depth as well as the recess length should start away from the loading point at a distance not less than 0.5h to avoid the critical region for shear failure. Finally, the current study proposed a method for calculating the deflection of non-prismatic beams with low reinforcement ratio(𝜌 = 0.7%) using the segmented beam method. It could be concluded that the analytical deflections estimates are in closer agreement with the experimental results, particularly for the lightly-reinforced concrete beams.