Microplane model for reinforced-concrete planar members in tension-compression

Existing microplane models for concrete use three-dimensional spherical microplanes in the analysis of two-dimensional planar members as well as three-dimensional members. Also, they do not accurately describe the postcracking behavior of reinforced concrete in tension-compression. In this study, a new microplane model is developed to overcome the disadvantages of the existing models. Instead of the existing spherical microplanes, the proposed microplane model uses disk microplanes involving a less number of microplanes and two-dimensional stresses and strains. As the result, the proposed model is more effective in numerical calculation. Also, the concept of the strain boundary is introduced to describe accurately the compressive behavior of reinforced concrete with tensile cracks in tension-compression. The validity of the proposed model was verified by comparison with existing experiments. In this paper, the microplane model and the numerical techniques involved in the finite-element analysis are described in detail.