• Linear Elastic
• P-Delta
• AISC Direct
• Buckling
• Geometric Non-Linear

• None - no analysis results is included
• Load Data - prints all the load data
• Mode Shape - prints mode shape values at the joints for all calculated mode shapes
• Statics Check - provides a summation of the applied loads and support reactions as well as a summation of moments of the loads and reactions taken around the origin
• Statics + Node - provides everything that the Statics Check does, as well as a summation of all internal and external forces at each joint. This option potentially generates a large volume of output.
• Statics + Load - this option is equivalent to the Load Data plus the Statics Check options.
• Statics + Load + Node - This option is equivalent to Load Data plus the Statics + Node options.

Specify the number of iterations to be performed. If specified, the program will perform the specified number of iterations whether or not the solution converges.

P-Delta analysis including stress stiffening effect of the KG matrix. With this option the global stiffness is adjusted with every iteration.

A regular STAAD.Pro P-Delta Analysis performs a first order linear analysis and obtains a set of joint forces from member/plates based on the large P-Delta effect. These forces are added to the original load vector. A second analysis is then performed on this updated load vector (5 to 10 iterations will usually be sufficient).

In the new P-Delta KG Analysis, that is, with the Kg option selected, the effect of the axial stress after the first analysis is used to modify the stiffness of the member/plates. A second analysis is then performed using the original load vector. Large & small P-Delta effects are always included (1 or 2 iterations will usually be sufficient).

Select this option to include both P-small and large Delta effects (recommended), sometimes referred to as P-δ & P-Δ. Leave this box unchecked to only include P-Δ effects (P- Large Delta).

Without the Small Delta option (i.e., a default STAAD.Pro P-Delta analysis), STAAD.Pro performs a first order linear analysis and obtains a set of joint forces, from members/plates based on the large P-Delta effect, which are then added to the original load vector. A second analysis is then performed on this updated load vector.

With the Small Delta option selected, both the large & small P-Delta effects are included in calculating the end forces, (5 to 10 iterations will usually be sufficient).

Select if the design methodology is Load Resistance and Factor (LRFD) or Allowable Stress (ASD).

Specify the maximum number of 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.

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.

Check this box to instruct the program to iterate Tau-b.

Tau

The limit to the change in the τ_b value in each iteration. If this value is exceeded by any member, then an additional iteration will be required unless the maximum number of iterations has been achieved

Displacement

The limit to the change in the maximum displacement in each iteration. If this has been exceeded, then an additional iteration will be required unless the maximum number of iterations has been achieved.

• Iterative - When this option is selected, the program will perform a P-Delta analysis including Kg Stiffening (geometric stiffness of members & plates) due to large & small P-Delta effects. If a non-singular stiffness matrix can be created, then buckling has not occurred. Then the load is increased from the last increment repeatedly until buckling does occur. Then the load is decreased halfway back to the prior increment. This bounds the buckling factor between the last 2 increments. Then STAAD.Pro proceeds to halve the interval until either the change between increments is 0.1% of each other, or the specified number of increments has been exceeded. The resulting factor is reported in the output file. The buckling deformed shape is simply the deformed shape from a static analysis with the near buckling load applied. This could appear more like a crushing, small displacement shape rather than a buckling mode shape. At least 15 iterations are recommended. Buckling will be applied to all primary cases.
• Eigen - This buckling method may only be used if an Advanced Analysis license is available. When using the Advanced Solver, the corresponding "buckling modes" are included in the output file.

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.

Specify the maximum number of iterations to achieve equilibrium in the deformed position to the tolerance specified.

Specify 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 steps. Value should be in current length units.

For convergence, two successive iteration results must have all displacements the same within this tolerance. Value entered is in current units.

Frequency of rebuilds of the tangent K matrix per load step & iteration.

• Once per load step
• Every load step & iteration

Select this option to add the geometric stiffness, KG, to the stiffness matrix, K.

Check this option to specify a target displacement value along or about the selected DOF for the monitored Node.