A nonlinear static analysis is performed using the initial Newton-Raphson method, done using the command snippet shown below. The maximum load the structure can bear, or its load limit is identified in this problem by divergence of the global Newton-Raphson solution (See Boundary Conditions and Loading).

The in situ stress state is calculated in a single substep.

The load limit is calculated using an initial time-step size of 0.05. To closely capture the loss of structural integrity, the time increment can be reduced to 0.001 and the number of equilibrium iterations increased to 50 for the load limit analysis.

To accomplish the above, specify details of step controls as shown in the following figure, and include the command snippet below.

Figure 49.5: Step Controls

Command Snippet

/SOLU                   ! ENTER SOLUTION
NROPT,INIT              ! Using Initial Stiffness Matrix
NEQIT,50                ! Number of Equilibrium iterations
NCNV,2                  ! Terminate analysis, not program exec
ERESX,NO                ! Copy integration point results to nodes