Modeling uplift and foundations on soil supports

Before running nonlinear analysis on a SAFE model, we recommend verifying the stability of the model under linear cases by checking the analysis run through Run > Last Analysis Run Log.

One common solution to convergence problems is providing  lateral supports for in-plane reactions along the X and Y axes. Note that soil supports only resist vertical loading along the Z axis. To provide lateral support, we recommend using springs with stiff proprieties in the  X and Y local axis, then those springs may be assigned along the edges/corners of the mat. Alternatively, a 2D-plate analysis may be run by selecting Run > Advanced Modeling Options, though in-plane axial forces will be neglected (2D analysis is never recommended for models with walls above).

Additional notes on the modeling of uplift include the following:

• Convergence. Uplift analysis might not converge when stabilizing forces are insufficient to counteract uplift forces. You can check numerical issues and convergence issues via Run>last analysis run details. It also helps to rerun the model with the non converging cases as linear and review deformations to help narrow down the  issues.
• Response Spectrum Results. Uplift analysis  is anon-linear type of analysis, because of the nature of the method results from RSA are absolute and do not have sign or direction, hence they should  not be used in an uplift analysis.

Review watch and learn videos 9 and 10 below:

Available at https://www.csiamerica.com/products/safe/watch-and-learn