Equivalent confining stress-based strength model for concrete under triaxial compression

•A rich database of 351 test results that covers a wide parameter range is assembled.•Concept of equivalent confining stress is proposed and calculation method is given.•An equivalent confining stress-based Power-law failure criterion is established.•By the model evaluation, this simple model has good accuracy and wide applicability. In order to predict the peak strengths for different strength grades, types, or shapes of concrete under equal or unequal triaxial compression, the concept of equivalent confining stress is firstly proposed and then its calculation method for concrete specimens in the shape of a cube, an annulus, or a cylinder is illustrated. Next, a straightforward power-law type of prediction model is developed based on the aforementioned equivalent confining stress by comparing the following three common failure criteria adopted in triaxial compression: the Mohr-Coulomb failure criterion, the Willam-Warnke failure criterion, and the Power-law failure criterion. Furthermore, a rich experimental database that covers a wide parameter range is established according to the triaxial test results reported in previous literature. The model is thoroughly evaluated after calibrating the coefficients in the modified Power-law failure criterion. From the subsequent evaluation result, the proposed model can provide an accurate prediction for concrete under uniform or non-uniform triaxial compression. Besides, it also works effectively for different strength grades, types, or shapes of concrete specimens. In fact, in different conditions, the mean ratios of predicted-to-test peak triaxial strengths are all around unity, and the degrees of volatility of predicted results are all at a low level. In brief, this easily usable equivalent confining stress-based strength model can accurately predict the peak triaxial compressive strengths of concrete.