Nonlinear Finite Element Analysis of High-strength Reinforced Concrete Beams with Severely Disturbed Regions

Abstract

The inclusion of D-regions within a reinforced-concrete member may affect largely the general behavior of the structure. Different techniques and approaches were proposed to control the behaviour of D-regions, such as the shear-friction approach and the STM model. Such proposals may not be applicable for all types of Dregions. The current work presents a nonlinear finite element model using the ANSYS software, that is adopted to study three types of D-regions, which are dapped ends, deep beams with openings and beams with loaded openings. The results revealed that the proposed FE model predicted adequately the effects of the inclusion of D-regions in RC beams. It is found that reducing the hanger or the nib reinforcement of a dapped end by 25% resulted in reducing capacity by 15% and 32%, respectively. Also, the results showed that for these deficiently reinforced dapped ends, reducing a/d ratio from 1.5 to 0.75 improved capacity by 23% and 36%. For the deficiently shearreinforced flanged deep beams, it was found that the inclusion of large openings within the shear span resulted in a capacity drop by (41-49) %. An enhancement of 23% was obtained when using stirrups of 12mm on both sides of the openings. Moreover, it is confirmed that the optimum location of the openings is under the diagonal path. Furthermore, it has been concluded that for loaded openings, the use of T-rolled sections within the bottom chord of the opening yielded an enhancement of 23% relative to the rhombus-shaped configuration. KEYWORDS: Dapped ends, T-deep beams with openings, Loaded openings, Hanger reinforcement.