# Options dialog

This dialog is used to set units, analysis model options, and model display controls.

Opens when either:
• Options is selected from the File menu, or
• Options is selected from the right-click pop-up menu in the view window

## Units tab

SettingDescription
Units system
Select the system of units to use for modeling:
• Metric - international decimal system of units
• English - imperial system of units
Units configuration Select a unit to use for each of the following measurements:
• Length
• Force
• Rotation
• Damping
• Displacement
• Section Dimension
• Moment
• Distributed Force
• Spring Stiffness
• Rotational Spring Stiffness
• Thermal contraction coefficient
• Area
• Density
• Distributed Moment
• Length6
• Pressure
• Rotational Mass
• Rotational Spring Stiffness for Linear Support
• Second Moment Area
• Section Modulus
• Spring Stiffness for Linear Support
• Length Tolerance
• Volume
• Section Area
• Stress
• Angle

## Analysis model tab

SettingDescription
Add intermediate nodes at intersections This option determines if two intersecting bars (i.e., members that have a common intermediate point) will be considered connected. If this option is deactivated, the two members are considered independent. It should be noticed that the tolerance to consider when two members intersect each other is very small.
Segment members The option Segment member is enabled by default. If this option is disabled, members will not be segmented.
Segment surfaces The option Segment surfaces is enabled by default. If this option is disabled, surfaces will not be segmented.
Mesh type This option asks the user for the input whether the mesh type will be Quadrangular (4 noded) or Triangular (3 noded). By default, the option is set to Quadrangular.
Maximum allowed distance between nodes The maximum distance allowed between nodes defines the distance for the meshing of the finite element (i.e., analytical) model.
Merge nodes tolerance The minimum allowable distance between nodes. If the distance between nodes is smaller than the tolerance the program assumes the nodes as only one node.

In order to get a correct segmentation of physical members (bars and plates), the value of the tolerance or maximum distance between physical members and intermediate nodes should be fixed. This tolerance allows filtering other surrounding nodes. The value of this parameter is usually small, but according to the geometry, bigger values can be used.

Out of Plane tolerance The tolerance value used for model integrity checks as well as for fixing warped surfaces.
Combination Method Select the method of how loads are combined:
• Analytical superposition – this method adds load combinations normally which is appropriate for linear, first-order elastic theory
• Primary load cases with Repeat – load combinations are added as repeat loads in the analytical model which should be used for any non-linear analysis

## Visualization tab

SettingDescription
Selection Cutback Percentage When objects are drawn in the view area of STAAD.Pro Physical Modeler, they are scaled away from the true extents for clarity. Members, surfaces, and area loads do not fully extend to nodes so as to help identify those nodes as well as other objects. This is called the "selection cutback." You can control the percent of this setback between values of 1% up to 25% of the objects dimensions.
SettingDescription
Members The percentage of the member length which is cut back from the end supports.
Surfaces The percentage of the surface edges which are cut back from the actual edge.
Area loads The percentage of the area load edges which are cut back from the actual edge.

## ISM tab

Used to save settings for exchanging model data via ISM.

SettingDescription
Interop
SettingDescription
Loads Check to import load cases and combinations from ISM.
Unused objects Check to import data even if not used in the model (e.g., a section size that is not assigned to any member).
Member alignment The cross-section positioning are updated based on the member alignment in the ISM repository with respect to the supporting joints. If not checked, then the analytical member aligns with the geometric center of the cross-section.
Alignment method
Select one of the following methods:
• None - If the model does not contain nodes then it creates analytical nodes
• Move nodes to analytical lines - If the model does not contain nodes then it creates analytical nodes and aligns the nodes to nearest members according to their analytical locations.
• Move nodes to most common plane - If the model does not contain nodes then it creates analytical nodes and attempts to improve the given node locations by moving nodes to common planes.
• Move nodes to both (above) - It performs the second process followed by the third.
Tolerances for fixing nodes
SettingDescription
Connectivity Tolerance The maximum separation between members considered to be connected.
Node merging tolerance No nodes will be added to the model that are closer to another node than this distance.
Node member separation factor A multiplier (1.0 or greater) that prevents removal of nodes that are further from a member than expected. Using a factor of 1.0 will match (as much as possible)
Plane tolerance To improve any node's locations by moving it to common planes is determined by this tolerance. The common planes that are considered are those defined by the member axes, possibly shifted by up to the given Plane tolerance.

## Dynamic tab

SettingDescription
Modal Analysis
SettingDescription
Calculate Eigen Solution Check this option to request a modal analysis.
Note: If a time history or response spectrum load case has been added, then a modal analysis is required and cannot be unchecked.
Eigen Method
• Subspace – the default subspace iteration method
• Arnoldi/Lanczos – Instructs the solver to use Arnoldi/Lanczos method for extraction of eigen vectors.
• Ritz Vector – Use load dependent Ritz vectors method for extraction of eigen vectors.
Set Number of Modes Check this option to specify the highest frequency (cycle/sec) to be considered for the dynamic analysis. Type the Value to use.
Shift Modes (for when Set Number of Modes is checked) Check this option to specify a number of eigen vectors per shift. This option is used when the solver fails to extract the Set Number of Modes due to insufficient memory.
Set Shift Frequency (for Arnoldi/Lanczos method only) Check this option to specify the frequency to be used as an initial shift. The solver will look for eigenvalues close to the shift. The eigenvalues found may not necessarily be the smallest values (i.e., closest to zero). If a full scale eigen solution is required, then this option should not be used.
Set Max Frequency Check this option to set the highest frequency (cycle/sec) to be considered for dynamic analysis.
Time History
SettingDescription
Time Step Type the solution time step used in the step-by-step integration of the uncoupled equations. Values smaller than 0.00001 will be reset to the default value of 0.001389 seconds.
Include Missing Mass Check this option to include the missing mass procedure in the time history analysis.
Set Max Time History Check this option to specify an ending time for a time history analysis in the Value field. If not specified, the time history will end when the last forcing function ends.
Damping
SettingDescription
Modal Damping
• Single – a single specified value used by all modes.
• Specify – explicitly defined modal damping ratios to use for some or all modes.
• Composite – based on values specified for each material. No additional values are provided here.
• Evaluate – modal damping which is calculated for all modes.
Damping Ratio For Single damping, type the Damping Ratio to use for the entire structure. A value of 0.05 is used by default.
Damping Ratios For explicit damping ratios for each mode, click in the Damping Ratios to display the modal damping table. Type the Damping value to use with each mode. A value of 0.05 is used by default for the first six modes.
Interpolation Select the method of interpolation to use for Evaluate modal damping:
• Calculated – the values of modal damping are determined based on Minimum Damping Ratio and Maximum Damping Ratio provided.
• Specified – the values of the modal damping are evaluated based on specified mass-proportional factor, Alpha, and stiffness-proportional factor, Beta. The minimum and maximum modal damping values are used as lower and upper limits for the evaluated damping values. Default values are provided for both methods.
Response Spectrum
SettingDescription
Modal Combination Select the method of combining the responses from each mode into a total response.
SRSS
Square Root of Summation of Squares method.
ABS
Absolute sum. This method is very conservative and represents a worst case combination.
CQC
Complete Quadratic Combination method (Default). This method is recommended for closely spaced modes instead of SRSS.
Resultants are calculated as:
$F=∑n∑mfnρnmfm$
where
 ρnm = $8ζ2(1+r)r2/3(1−r2)2+4ζ2r(1+r)2$ r = ωn/ωm ≤ 1.0
Note: The cross-modal coefficient array is symmetric and all terms are positive.
ASCE
NRC Regulatory Guide Rev. 2 (2006) Gupta method for modal combinations and Rigid/Periodic parts of modes are used. The ASCE4-98 definitions are used where there is no conflict. ASCE4-98 Eq. 3.2-21 (modified Rosenblueth) is used for close mode interaction of the damped periodic portion of the modes.
TEN
Ten Percent Method of combining closely spaced modes. NRC Reg. Guide 1.92 (Rev. 1.2.2, 1976).
CSM
Closely Spaced Method as per IS:1893 (Part 1)-2002 procedures.
GRP
Closely Spaced Modes Grouping Method. NRC Reg. Guide 1.92 (Rev. 1.2.1, 1976).

The CQC and ASCE4-98 methods require damping. ABS, SRSS, CRM, GRP, and TEN methods do not use damping unless spectra-period curves are made a function of damping (see File option below). CQC, ASCE, CRM, GRP, and TEN include the effect of response magnification due to closely spaced modal frequencies. ASCE includes more algebraic summation of higher modes. ASCE and CQC are more sophisticated and realistic methods and are recommended.

For the ASCE method, type the f1 and f2 frequencies for ASCE 4-98.

Missing Mass Check this option to use the "Missing Mass" method to include the static effect of the masses not represented in the modes.
Note: For the ASCE combination method, this option is automatically checked.
SettingDescription
Set Spectral Acceleration Check this option to specify the spectral acceleration to use for the missing mass mode. Type the Value (with length/sec2 units). If not specified, then the spectral acceleration at the Zero Period Acceleration frequency is used. If the ZPA frequency is also not specified, then the spectral acceleration at a frequency of 33 hz is used.
Set Zero Period Acceleration Frq Check this option to specify a frequency at which the corresponding spectral acceleration value is used for the missing mass mode. For this option, the spectral acceleration at the Value (entered in Hertz) is used. If not specified, then a frequency of 33 hz, and thus the corresponding spectral acceleration at that frequency, is used.
Sign of Results
• Unsigned – No sign is assigned to the combined results.
• Largest Effect – his option results in the creation of signed values for all results. The sum of squares of positive values from the modes are compared to sum of squares of negative values from the modes. If the negative values are larger, the result is given a negative sign. This command is ignored for ABS option.
• Highest Participation – All results will have the same sign as the mode with the greatest percent participation in the excitation direction.
• Dominant – The dominant mode method. All results will have the same sign as the Mode number specified alone would have if it were excited then the scaled results were used as a static displacements result. If not specified, the first mode is used. Must be an integer greater than zero.