When setting up a load-limit analysis for a reinforced concrete model, consider the following recommendations:
Make use of symmetry conditions whenever possible to stabilize the numerical model.
Competing crack-growth can lead to bifurcation problems and, therefore, to a loss of numerical convergence before the load limit is reached. Avoid the problem by defining custom weak points in the simulation model so that cracks form in well-defined regions.
Use an initial Newton-Raphson nonlinear solution method to better capture the point of instability.
Compared to a load-controlled analysis, the structural behavior after loss of stiffness can be more easily traced via a displacement-controlled analysis; however, if the region of instability is of concern and a load-controlled analysis is necessary, consider using the arc-length method (ARCLEN).
Using the arc-length method, the region of instability is identified at a load of approximately 610 kN and a deflection of 5.6 mm. The results correspond to those of the analysis shown in Figure 49.4: Reaction Force/Displacement Curve: Load-Limit Analysis, validating the calculated load limit.
