A four-parameter multi-axial strength criterion for lightweight aggregate (LWA) concrete

Concrete utilized in engineering structures is usually subject to the action of multi-axial stress. The strength theory of concrete is significant to structure design and saving of construction material. Experimental results have revealed that lightweight aggregate (LWA) concrete represents platform flow plasticity under high compressive stress. The ultimate strength surface of LWA concrete under multi-axial stress intersects with the hydrostatic stress axis at two different points, which is completely different from that of the normal concrete as the ultimate strength surface is open-ended. So the strength criterion aimed at normal concrete cannot fit LWA concrete. In this paper, a four-parameter multi-axial strength criterion for LWA concrete is presented. The strength envelope of the proposed model in the deviatoric plane adopted elliptic curve similar to that of Willam-Warnke model, and the tensile and compressive meridians are represented by quadratic functions with four parameters. Two methods can be used for the determination of the four parameters and their merits and drawbacks are compared by the analysis of experimental data.