Saw-tooth softening model for reinforced concrete structures

The non-linear behaviour of reinforced concrete structures strongly depends on abrupt cracking phenomena. The crack pattern prediction is fundamental to the reliable assessment of the structure, both at the service and at the ultimate limit states. The Non-linear Finite Element (NLFE) analysis is the common tool to perform these verifications. Unfortunately, the constitutive models for RC material are characterized by softening stress-strain relationships, which involve negative tangent stiffness. Therefore, the incremental-iterative solution procedure often leads to numerical instability and divergence problems, especially when the energy dissipated by cracking and crushing phenomena is little compared with the elastic energy stored in the structure. In this paper, the sequentially linear approach is proposed as an alternative to incremental convergence methods. The robustness and effectiveness of themethod is proved through plane concrete and RC case studies.