Numerical analysis of shear behaviour of high-strength concrete beams without shear reinforcement

The aim of this study was to elucidate the unexpected reduction in the diagonal shear strength of high-strength concrete (HSC) beams with an increase in concrete strength. The modified compression field theory (MCFT) was used to examine 298 beams and girders for shear. The diagonal shear strengths were predicted using available international standards and the model proposed by Kim and Park (1996). The MCFT-based analysis tool Response-2000 was found to be the most effective method for evaluating the shear strength (V) of normal-strength concrete beams (f_ck < 42 MPa), yielding an average V_exp/V_pred of 1.117 and a standard deviation (SD) of 0.204. Compared with existing models, the Kim and Park (1996) model was more efficient in determining the diagonal shear strength of HSC beams (42 ≤ f_ck < 70 MPa), with an average V_exp/V_pred of 0.898 and SD of 0.295. However, since high-strength shear behaviour is a function of aggregate size, by incorporating the significance of aggregate action, a model was developed to predict the aggregate size for concrete compressive strength of 42–70 MPa. The proposed model was able to accurately predict the diagonal shear strength with an average of 0.927 and a SD of 0.303 for f_ck = 42–70 MPa.