A lack of a widely accepted laboratory procedure for determining concrete shear strength remains a significant obstacle to consistent comparison of experimental results and calibration of analytical models. Unlike established shear setups, the proposed method uses controlled boundary conditions and a simple specimen to minimise parasitic effects and promote a shear-dominated response. This paper presents a novel experimental setup for evaluating the Mode II (in-plane shear, sliding along a crack plane) shear strength of plain high-strength concrete, and establishes the baseline response, validity, and sensitivity of the setup. An experimental programme was conducted on six plain high-strength concrete mixtures (compressive strength \(f_c \approx 60\) –80 MPa) to isolate mix-design effects through controlled variations in mixture parameters. Mixtures were tested under four distinct loading configurations: fully compressed, partial compression, mixed-mode compression, and shear-dominated, to capture the transition from measuring compressive strength to shear strength. Complementary finite-element simulations in ATENA were conducted to investigate how each configuration influences the stress state and to verify the experimentally observed failure modes. Pearson correlation coefficients between configuration-specific peak stresses indicate that the shear-dominated configuration shows weak-to-moderate coupling with the other configurations ( \(r=0.17\) with fully compressed; \(r=0.41\) with partial compression; \(r=0.36\) with mixed-mode compression), supporting that its peak response is comparatively distinct from the compression-governed regimes. Comparison with selected shear-strength estimation models based on different setups yielded close agreement in the investigated strength range, with most points for the best-performing models lying within the ±15% band and mean absolute error (MAE) values of 0.48–1.21 MPa. Both correlation analysis and analytical comparison support the hypothesis that the proposed setup provides a reliable and practical baseline for isolating shear-dominated response, enabling improved comparison between studies and supporting future standardisation of shear strength testing in concrete.
