Prediction of shear strength of reinforced concrete beams using displacement control finite element analysis

This research resulted in the development of a new method for performing displacement control analysis of distributed loads to obtain the ultimate shear strength of structural components. A framework, consisting of several sub-frames, was designed to convert the single displacement applied at the top of the framework to equivalent uniformly-distributed forces applied to the beam. The shear capacity of beams under a concentrated load at mid-span was compared with the shear capacity of a uniform load for four different a/d ratios (3, 4, 5, and 7). The results indicated that the strain in the longitudinal rebar, which is dependent upon the loading condition, strongly impacts the shear strength of a critical section of structural components. The shear strength of the critical section of the R.C. beams studied in this research had uniformly distributed loads that were, on average, 76% greater than the shear strength of the same beam with a concentrated load at mid-span. The shear strength prediction of the AASHTO specification as well as ACI318-14 code were evaluated for beams with shear behavioral mode. A parametric study of 24 RC beams was conducted, and the results indicated that AASHTO's prediction for strain in longitudinal rebar differs about 19%, on average, from the results of the finite element method (FEM). For prediction of the β factor, however, the difference is about 61%. The ACI318-14's formulation for the concrete shear strength (Vc) averages 59% higher than the FEM results for the studied beams.