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This paper presents an integrated model for the shear friction strength of monolithic concrete interfaces derived from the upper-bound theorem of concrete plasticity. The model accounts for the effects of applied axial stresses and transverse reinforcement on the shear friction action at interfacial shear cracks. Simple equations are also developed to generalise the effectiveness factor for compression, the ratio of effective tensile to compressive strengths and the angle of concrete friction. The reliability of the proposed model is verified through comparisons with previous empirical equations and 103 push-off test specimens compiled from different sources in the literature.The previous equations considerably underestimate the concrete shear transfer capacity and the underestimation is notable for interfaces subjected to additional axial stresses. The proposed model provides superior accuracy in predicting the shear friction strength, resulting in a mean between experimental and predicted friction strengths of 0·97 and low scatter. Moreover, the proposed model shows consistent trends with the test results in evaluating the effects of various parameters on the shear friction strength.

This study proposes a simple and rational stress-strain relationship model applicable to brick masonry under compression. The brick prism compression tests were conducted with different mortar strengths and with constant brick strength. From the observation of the test results, shape of the stress-strain curve is assumed to be parabola. In developing the stress-strain model, the modulus of elasticity, the strain at peak stress, and the strain at 50% of the peak stress on the descending branch were formulated from regression analysis using test data. Numerical and statistical analyses were then performed to derive equations for the key parameter to determine the slopes at the ascending and descending branches of the stress-strain curve shape. The reliability of the proposed model was examined by comparisons with actual stress-strain curves obtained from the tests and the existing model. The proposed model in this study turned out to be more accurate and easier to handle than previous models so that it is expected to contribute towards the mathematical simplicity of analytical modeling.

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