An improved Lubliner strength model based on Ottosen failure criterion for concrete under multiaxial stress state

The Lubliner strength criterion (SC) can achieve desirable responses in the tension-dominated and plane compressive stress states but overestimates the concrete strength under triaxial compression. Moreover, additional breakpoints without continuous derivatives occur along the hydrostatic pressure axis. The primary causes for these problems include the Lubliner SC constant gamma parameter and breakpoints along the piecewise linear meridians. Therefore, a new Lubliner-Ottosen SC is developed with the parameter gamma determined based on the Ottosen SC. The meridian contains smoothly connected straight and curved lines. Moreover, the deviatoric traces of the corresponding failure surface gradually change from curved triangles to approximate circles with increasing hydrostatic pressure. Finally, the proposed Lubliner-Ottosen SC is compared with other failure criteria and experimental results for concrete. Regardless of triaxial or nontriaxial compression, the new criterion can suitably represent the failure behavior of concrete in the various multiaxial stress states.