Nonlinear Analysis tab
Used to direct STAAD.Pro to perform a nonlinear analysis which can account for nonlinear effects of moderate displacement and small strain. This solution holds for where the element distortion is small and small rotations are assumed.
Refer to TR.37.8 Geometric Nonlinear Analysis for additional information.
The first analysis step must be stable, otherwise use ARC control to prevent instability. The procedure does not use follower loads. Loads are evaluated at the joints before the first step; then those loads translate with the joint but do not rotate with the joint. Equilibrium is computed in the displaced position.
Nonlinear entities such as tension/compression members, multilinear springs, gaps, etc. are not supported when using a nonlinear analysis. Additionally, nonlinear analysis does not account for postbuckling stiffness of members.
The values for the Displacement Limit are used to limit analysis cycle to a specified displacement value and degree of freedom for a monitored node. When two or more Load Steps are specified, the calculated displacement or rotation is compared to the Target Value along or about the DOF for the specified Node each step. If the calculated displacement or rotation meets or exceeds the target value, then the analysis is stopped.
Setting  Description  

ARC 
Specify a displacement control, which is the value of the absolute displacement limit for the first analysis step. If the maximum displacement is greater than this limit, ARC will calculate a new step size for the first step and a new value for Load Step. Value should be in current length units. 

Iterations  Max. Number of iterations to achieve equilibrium in the deformed position to the tolerance specified.  
Tolerance  For convergence, two successive iteration results must have all displacements the same within this tolerance. Value entered is in current units.  
Load Steps  Specify the number of load steps to be used. Load is applied in stages if entered. One means that all of the load is applied in the first step.  
Rebuild Steps 
Frequency of rebuilds of the tangent K matrix per load step & iteration.


Use KG  Select this option to add the geometric stiffness, KG, to the stiffness matrix, K.  
Node  Enter a node number or click […]. to enter the selected node to monitor during the geometric nonlinear analysis.  
DOF  Select the degree of freedom to monitor during the analysis for specified Node.  
Target Value  Specify a target displacement value along or about the selected DOF for the monitored Node.  
Print Option  Standard STAAD.Pro analysis print options:
