Non-linear finite element analyses applicable for the design of large reinforced concrete structures

In order to make non-linear finite element analyses applicable during assessments of the ultimate load capacity or the structural reliability of large reinforced concrete structures, there is need for an efficient solution strategy with a low modelling uncertainty. A solution strategy comprises choices regarding force equilibrium, kinematic compatibility and constitutive relations. This contribution demonstrates four important steps in the process of developing a proper solution strategy: (1) definition, (2) verification by numerical experiments, (3) validation by benchmark analyses and (4) demonstration of applicability. A complete solution strategy is presented in detail, including a fully triaxial material model for concrete, which was adapted to facilitate its implementation in a standard finite-element software. Insignificant sensitivity to finite element discretisation, load step size, iteration method and convergence tolerance were found by numerical experiments. A low modelling uncertainty, denoted by the ratio of experimental to predicted capacity, was found by comparing the results from a range of experiments to results from non-linear finite element predictions. The applicability to large reinforced concrete structures is demonstrated by an analysis of an offshore concrete shell structure.