136 Structure User's Guide However, if you select the Custom Sketching Plane option on the ribbon, the software
prompts you to select a boundary plane (usually an elevation plane). The boundaries that you defined on the custom boundary plane are projected parallel to the Z-axis (right side of the figure).
Define Boundaries - Define the outside boundaries of the slab. You can define the slab boundaries by selecting objects in the model. If you select objects in the model and those objects are moved, the software automatically resizes the slab to maintain the boundary relationship. For example, you can select the outside edge of a beam flange as a boundary along one side of a slab.
Later, if the section size for the beam is changed and the flange edge moves out an inch, the software automatically moves the edge of the slab an inch to match the new location of the flange edge.
Define Boundary Offsets - Activates the Boundary Offsets dialog box. This dialog box allows you to define an offset distance for each boundary that you have defined. Select a row to highlight the boundary in the model. Then, type the distance from the boundary to place the edge of the slab. Type 0 to place the slab edge on the boundary. Type a negative number to offset the slab inside the boundary. Type a positive number to offset the slab outside the boundary.
Finish - Places the slab using the defined parameters.
Plane Method - Specifies how you want to define the support plane. This option is only available when you are defining the support plane.
Select Coincident to specify that you want the slab placed on the support plane.
Select Offset from a Plane to place the slab a specified distance from the support plane. If you choose this option, you must define the offset distance.
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Select Angle to plane to place the slab at a specified angle or slope to the support plane. If you choose this option, you must define an axis of rotation and the angle or slope.
Select Vector & Point to specify the support plane using two points to define a vector normal to the plane and a third point to define the plane position along the vector.
Select 3 Point Plane to specify the support plane using three points that you specify in the model.
Offset - Specify the offset distance for the slab from the selected support plane. You can specify the offset dynamically in graphics or by typing the distance. This option is only available when Plane Method is set to Offset from a Plane. Click Lock/Unlock to lock the offset distance.
Angle - Specify the angle at which to place the slab relative to the support plane. You have to define the axis of rotation using two points before you can define the angle. This option is only available when Plane Method is set to Angle to plane. Click Lock/Unlock to lock the angle.
Slope - Specify the slope at which to place the slab relative to the support plane. You have to define the axis of rotation using two points before you can define the slope. This option is only available when Plane Method is set to Angle to plane. Click Lock/Unlock to lock the slope.
Select Boundaries - Select this option to select objects in the model to define the slab boundaries. This option is only available when you are defining the slab boundaries.
Add References to Sketch 2D - Allows you to select which objects in the 3-D environment to see in the sketch 2-D environment when you are drawing the boundaries of the slab. The objects that you select will display as thick blue lines in the 2-D environment. You can define
relationships and dimensions to these blue-lined objects in 2-D. The software may also
automatically retrieve 3-D objects to display in the 2-D environment. The automatically selected objects will display as grey lines. These grey line objects are read-only (you cannot define relationships or dimensions to them) and are there to help you visualize the model. This option is only available when you are drawing the slab boundaries.
For slabs and walls defined in the sketch 2-D environment, SmartPlant 3D removes any constraints external to the defining group when you:
Copy a slab or wall. The original slab or wall will still have the constraints, however the newly created copy of the slab or wall will not have the external constraints.
Move a slab or wall. All external constraints are removed from the slab or wall.
Rotate a slab or wall. All external constraints are removed from the slab or wall.
The defining group is the lines (or other shapes) that you place in the sketch 2-D environment that define the actual slab or wall. An example of an external to the group constraint might be an edge of a Slab XZY offset from the edge of Slab 123. The constraint is between two different slabs (defined by two different groups) so it is removed. An example of an internal to the group constraint that is not removed might be one slab side constrained to be parallel to the opposite side. In this case both sides belong to the same slab, and hence the same group, and the constraint is therefore not removed.
Draw - Opens the sketch 2-D environment in which you can draw the boundaries of the slab.
You can draw multiple slabs at a time in the 2-D environment. This option is only available when you are defining the slab boundaries.
Select Patches to Compose the Slab - If the boundaries that you selected can form the boundary for the slab in more than one way, then you have defined an ambiguous boundary. The software prompts you to select one or more bounded areas to clarify the desired slab boundary.
For more information, see Solve Ambiguous Boundaries (on page 142).
138 Structure User's Guide Sketch 3D - Select this option to sketch the boundaries of the slab in the 3-D environment.
Cancel - Clears all selected planes or boundary objects.
Accept - Accepts all selected planes or boundary objects.
System - Select the parent system for the slab that you are placing. Systems are defined using the Systems and Specifications task.
Type - Select the type of slab to place, such as a slab on grade or composite deck. The properties change depending on the slab type that you select. You can define a custom slab type in the StructSlabGeneral.xls workbook in the reference data. Refer to the Structure Reference Data Guide for more information.
Composition - Select a slab composition from the list. Available compositions depend on the type of slab being placed. You can define a custom composition using the StructSlabGeneral.xls and StructSlabLayer.xls workbooks in the reference data. Refer to the Structure Reference Data Guide for more information.
Name - Displays the name of the slab that you are placing.
Priority - Select the priority to assign to the slab.
Face Position - Specifies how the slab is placed in the model with respect to the support plane. If this option is set to Center, the slab is placed with respect to its centroidal axis. If this option is set to Top, the slab is placed with respect to its top face. If this option is set to Bottom, the slab is placed with respect to its bottom face.
Total Thickness - Type the thickness of the slab. The default thickness is based on the selected slab type and composition.
If the slab has more than one layer, then the Total Thickness box is read-only. To edit the slab thickness, use the Layer tab of the Slab Properties dialog box. For more information, see Edit Slab Properties (on page 144).
Slab Assembly Connections
Slab assembly connections are similar to member assembly connections, but define the trimming and edges of slabs. Slab assembly connections are placed automatically when the slab is created.
The slab assembly connections are:
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The Slab by Member Boundary assembly connection is placed by the software when you select a member as a slab boundary.
The Slab Free Edge Assembly connection is placed by the software when you select a grid line as a slab boundary.
If a slab's bounding object (for example a member, a wall, or another slab) is deleted, then that deleted object is replaced as a boundary by the slab assembly connection which is generated from that deleted object. This behavior keeps the slab from going to the To Do List as missing a boundary.
Locating Slab Assembly Connections
Assembly connections do not display in the model. However, if you set the Locate Filter to Slab Assembly Connections, you can locate and select assembly connections for review and editing.
Assembly connections are located at the edges of slabs.
When you select an assembly connection, the software displays the assembly connection type in the ribbon. Select the Edit > Properties command to edit the assembly connection properties.