Question
How does MIDAS CAD support SPC for detailed section design?
Answer
The SPC (Section Property Calculator) feature in MIDAS CAD allows users to define section geometry and calculate section properties for use in structural analysis and design.
API Connection
To use the SPC Feature, you need to connect it first. If the 'Disconnect' button appears under the Apps tab, the API is connected.
Run SPC
Run SPC: Launch the SPC (Section Property Calculator) from the tool tree menu in MIDAS CAD. You can also run it by typing SPC in the Command window.
SPC Section Creation
Name: Displays the name of the section defined using the section creation feature.
Type: Displays the type of the section defined using the section creation feature.
Add: Executes the SPC (Section Property Calculator) section creation function.
Modify: Edits the calculated section property results.
Delete: Removes the calculated section from the list.
Preview: Displays a preview of the calculated section.
Close: Closes the CIVIL NX - SPC function.
Section Name & Type
Section Name: Enter the name of the section.
Section Type: Three types of sections are available: Plane, Line, and Composite.
SPC Section Definition – Plane Type
Select External Object: Select a closed outer object. Only the outermost closed boundary among the selected objects will be recognized.
Select Internal Object: Select closed inner objects. If there are multiple inner objects, select one closed boundary at a time in sequence.
Mesh Density: Select the level of mesh refinement.
SPC Section Definition – Line Type
Break all intersecting: Object spilitting based on line intersections.
Define Thickness: After selecting the line object, enter the thickness value. The entered thickness will be applied to the line object but will disappear once the "Section Property Calculator" window is closed. (The thickness will still be visible in the preview.)
Define Closed Section: Select the closed objects. If there are multiple closed objects, select each closed section one at a time.
Specify Curve Precision: For section property calculation, Splines and Ellipses must be divided into lines. Curve precision refers to the degree of this division.
Create with Steel Design Type: When checked, the "Design Group Setting" tab becomes active, allowing you to define the object information for Top, Bottom, Right Web, and Left Web.
When selecting the Top, Bottom, Right Web, and Left Web objects, stiffeners can be considered. The selected objects will be generated with the "Stiffener" label applied.
SPC Section Definition – Composite Type
The Composite Type section is created using pre-defined Plane Type and Line Type sections.
Material Settings: Click the […] button to activate the "Material Settings" window, where you can define the material name, elastic modulus, Poisson's ratio, and other properties.
The Base option is used to specify the Base Material, which serves as the reference for material substitution. (In composite sections, all materials must be converted into a single material type to calculate the overall section properties.)
Base Material: Displays the Base Material selected in the Material Settings.
Number of Parts: Selcect the number of parts to be included in the composite section.
CIVIL Section Property Calculation and DWG Table Settings
Specify the settings for section property calculation and table generation.
CIVIL Section Property Calculation: Calculates the section properties.
Note: Section property calculations are not performed based on the units specified below. Instead, the values are computed based on the numerical dimensions drawn in the DWG. When units are changed, the results are converted accordingly. Therefore, if a drawing created in millimeters (mm) is calculated with the unit set to meters (m), the result will be incorrect. Please ensure unit consistency.
Force Unit: Option to specify the force unit used in the table (e.g., kN, kgf, tonf).
Length Unit: Option to specify the length unit used in the table (e.g., mm, inch, ft).
Precision: Option to set the number of decimal places to be displayed.
Layer: Option to specify the layer for the table.
Font: Option to specify the font used in the table.
Options
Specify additional options.
Result Location: Option to select the position where the section results will be displayed.
Object Hatch: Option to enable or disable hatching for objects.
Mesh Density Preview Window
Preview
Displays a visual preview of the section.
Section Properties:
Asy: Effective shear area resisting shear force in the local y-axis direction
Asz: Effective shear area resisting shear force in the local z-axis direction
Ixx: Torsional resistance about the local x-axis
Iyy: Area moment of inertia about the local y-axis
Izz: Area moment of inertia about the local z-axis
Cyp: Distance from the neutral axis to the outermost point in the positive y-direction
Cym: Distance from the neutral axis to the outermost point in the negative y-direction
Czp: Distance from the neutral axis to the outermost point in the positive z-direction
Czm: Distance from the neutral axis to the outermost point in the negative z-direction
Peri: O: Total length of the outer perimeter of the section
Peri: I: Total length of the inner perimeter for hollow sections such as boxes or pipes
y1, z1: Distance from the neutral axis to Point 1, used in composite stress calculations
y2, z2: Distance from the neutral axis to Point 2, used in composite stress calculations
y3, z3: Distance from the neutral axis to Point 3, used in composite stress calculations
y4, z4: Distance from the neutral axis to Point 4, used in composite stress calculations
File Export
Sec Export: Exports a .sec file that can be imported into CIVIL NX.
DWG Export: Exports as a DWG file.
Excel Export: Exports as an Excel file.
Import from CIVIL NX
Imports section data from a file.
CIVIL NX Linked Sections
Name: Displays the name of the section saved as a CIVIL NX linked section.
Modify: Modifies the section saved as a CIVIL NX linked section.
Delete: Removes the selected section from the CIVIL NX linked section list.
Generate section: Generates a new section.
Export to CIVIL NX: Links the selected section(s) in the list with MIDAS CIVIL NX.
Preview: Displays a preview of the section to be linked.
Close: Closes the CIVIL NX - SPC function.
CIVIL Linked Section Type
Section ID: Enter the API format ID to be linked with CIVIL NX.
Section Name: Enter the name of the API format file to be linked with CIVIL NX. (Note: Only English characters are supported for section names.)
Value Type: Creates a Value Type section. When selected, the section list below displays Plane / Line / Design Type sections.
PSC Type: Creates a Prestressed Concrete (PSC) section. When selected, only Plane Type sections appear in the section list below, and the PSC Setting button on the right becomes active.
Param. for Design: Enter sectional dimensions used in design. These values are used for shear stress calculations.
For closed and open sections, the calculations are as follows:
Closed Section: kt = 2F · t
Open Section: kt = ∑ ⅓bt3
Where F is the area enclosed by the centerlines of thin plates, and t is the plate thickness. When applying Chinese design codes,
the calculation follows Roark’s Formula: kt =
8ab
3[1 + 0.6095(b/a) + 0.8865(b/a)2 − 1.8023(b/a)3 + 0.9100(b/a)4]
Thk. for Torsion (min.): Enter the minimum web thickness required for torsional stress calculation. The shortest web thickness should be specified to ensure the section is effective in resisting torsion.
Composite: Creates a composite section. When selected, the section list below displays Composite Type sections.
Tapered: Creates a section with varying size at both ends. When selected, the section list below displays Composite Type sections.
Shear Check: Calculates the shear force in regions vulnerable to shear in the PSC section. Enter Z1 and Z3 by selecting Shear Check. Qy and the web thickness for shear checking can be entered manually or automatically calculated by checking Auto.
Options
Consider Shear Deformation: Toggle this option ON/OFF to include or exclude shear deformation in the analysis.
Offset Settings: Opens the Change Offset dialog box.
Offset Settings
Center Loc.: Choose between the Centroid and Center of Section Dimensions as the reference for the section center.
Horizontal Offset: Specifies the horizontal offset position of the section.
to Extreme Fiber: When selected, the offset position defined under “Offset” will be applied, as shown in the reference diagram.
User: Select User to define a custom horizontal offset value.
Note: When the Offset option is set to "Center-Top", "Center", or "Bottom", the horizontal offset is fixed to Center, and the User option cannot be used. For tapered sections, the input field for J-end becomes active.
Offset: Specifies the location of the section center.
Vertical Offset: Specifies the vertical offset position of the section. Details are the same as for Horizontal Offset.
User Offset Reference: Defines the reference point when entering offset values manually using the User type.
Centroid: Applies the offset distance based on the section’s centroid.
Extreme Fiber(s): Applies the offset distance based on the specified location (Left/Right or Top/Bottom) set in the Offset option.
Tapered Section Settings
Y Axis Variation: Sets the tapering behavior along the Y-axis for Tapered General Sections. Options include: Linear, Parabolic, and Cubic.
Z Axis Variation: Sets the tapering behavior along the Z-axis for Tapered General Sections. Options include: Linear, Parabolic, and Cubic.
Linear: Section dimensions vary linearly along the local x-axis.
Parabolic: Section dimensions vary parabolically (quadratic) along the local x-axis.
Cubic: Section dimensions vary cubically (third-degree polynomial) along the local x-axis.