Investigation on Size Effect of Reinforced Concrete Deep Beams

Abstract

Since a diagonally cracked deep beam behaves as a tied arch, the conventional plane section remaining plane approach is not applicable to analyze of deep beams. A finite element modeling approach, which is used to predict the behavior of structures is becoming more popular instead of conducting the full experimental tests, since the efficiency of the model can be evaluated by the experimental results, the numerical models, shows a good agreement with the experimental analysis results. In this study RC deep beams were modeled and analyzed on ABAQUS, which is a nonlinear FE software, in order to investigate the size effect. The study variables are; Horizontal Reinforcement ratio (HRR), Vertical reinforcement ratio (VRR) and Material strength of concrete and Longitudinal Reinforcement ratio (LRR). The beams were grouped into five series, A, B, C, D and E based on shear span to depth ratio (av/d) of 0.4, 0.8, 1.2, 1.6, and 2.0 respectively. Horizontal shear bar ratio for all the RC deep beams specimens varies between 0.2% and 2.2% with an interval of 0.5%. Vertical shear bar ratio for all the RC deep beams specimens varies between 0.25% and 2.25% with an interval of 0.5%. Material strength of concrete varies from35 to 55MPa with an interval of 5MPa.The longitudinal reinforcement ratio for all the RC deep beams specimens varies between 0.2% and 2.2% with an interval of 0.5%. Before modeling the specimen, the software was validated with an experimental work. The validation results show that the experimental ultimate strength of beam was 96.97% of the same beam. The procedures used for the validation was also used in modeling all the specimens. Finally, the modeled beams are analyzed on ABAQUS version 6.14-5 and their load displacement diagrams were drawn. The ultimate load capacities of all the beams were determined from these load displacement curves and the percentage increase in the ultimate load capacity of all the specimen beams were determined. The results show that as the HRR increases from 0.2% to 2.2% the size effect was also found to increase from 0.4676% to 31.3104%, for all av/d ratios. When VRR increases from 0.25% to 2.25% the size effect was also found to increase from 0.0206% to 13.2862% for all av/d ratios. When concrete strength increases C-35 to C-55Mpa the size effect was also found to increase from 1.0496% to 9.2378%, LRR increases from 0.2% to 2.2% the size effect was also found to increase from 1.297011% to 20.88331%., for all av/d ratios.