Perform Direct Analysis tab
Used to instruct STAAD.Pro to perform a direct analysis per AISC 360 Appendix 7.This method accounts for the second order effects resulting from deformation in the structure due to applied loading, imperfections and reduced bending stiffness of members due to the presence of axial load.
This is a non-linear iterative analysis as the stiffness of the members is dependent upon the forces generated by the load. The analysis will iterate, in each step changing the member characteristics until the maximum change in any τb is less than the Tau tolerance. If the maximum change in any τb is less than 100x the Tau tolerance and the maximum change in any displacement degree of freedom is less than the Displacement tolerance; then the solution has converged for this case.
This analysis method is to be used in conjunction with Direct Analysis definition command. The Define Direct command should be added prior to instructing the program to perform this type of analysis.
Additionally, a direct analysis typically requires the definition of Notional Loads.
|Option||Select if the design methodology is Load Resistance and Factor (LRFD) or Allowable Stress (ASD).|
|No. of Iterations||Specify the maximum number of iterations.|
|PDelta Iterations||Select the number of iterations to be used for a PDelta with Small Delta analysis. Typically this should be from 5 to 25. The default number of 15 is recommended.|
|Reduced EI||Check this option to use the reduced EI (Tau-b × 0.8 ×EI) for member section moment & section displacement. Clear the check box to use the full EI value.|
|Perform Tau-b Iteration||Check this box to instruct the program to iterate Tau-b.|
|Print Option||Standard STAAD.Pro analysis print options: