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Creation/modification of the structure’s geometry and strut-and-tie model,
execution of the truss analysis, and stress checks using CAST Design Tool are
all done through the CAST Graphical User Interface (GUI). The CAST GUI that
appears on your screen will look similar to Figure 3.
This interface consists of several components as labeled in Figure 3.
Please familiarize yourself with the names of these interface components as they
will be used throughout this handout.
Figure 3 A Typical CAST Window
(Click here
to view a larger image)
Notes:
- The screen shown in this handout may look slightly different from your
computer’s screen due to different toolbar positions and different settings of screen resolution and fonts.
- In addition, several terminologies used in CAST Design Tool are explained below:
- D-Region Boundary:
- A closed, non-intersecting polygon that defines the geometry of the structure.
- There are two types of D-Region Boundaries: Outer Boundary
(Perimeter) and Inner Boundary (for openings).
- You are allowed to create only one Outer Boundary, but you can create as many Inner Boundaries
as you want.
- Because there is only one Outer Boundary that should exist in your model and the region inside the Outer Boundary represents the concrete continuum, you are not allowed to copy, cut, or remove it from your model once you create it. However, you are surely allowed to change the positions of the Boundary Corners. You are also allowed to add and remove Boundary Corners as you wish.
- D-Region Boundary Corner:
- Intersection of two Boundary Edges.
- D-Region Boundary Edge:
- Line connecting two Boundary Corners.
- Place for STM Nodes that possess Bearing Plates, Point Loads, or Point Supports.
- Strut-and-Tie Model:
- Internal truss in the D-Region.
- Consists of STM Elements interconnected at STM Nodes.
- STM Element:
- Component of Strut-and-Tie Model.
- STM Elements can be in the form of Struts (compressive STM
Elements) or Ties (tensile STM Elements).
- STM Elements have Effective Widths, representing the extent of idealized compressive stress fields
(for Struts) or tensile stress fields (for Ties).
- STM Node:
- Component of Strut-and-Tie Model.
- Place where one or more STM Elements meet, also called a nodal zone.
- There is only one STM Element allowed to frame into an STM Node
having Bearing Plates, Point Loads, or Point Supports.
- Stabilizer:
- STM Element whose member force is zero.
- Stabilizers are not included in the nodal zone construction.
- Stabilizers are required to avoid ill-conditioned structure stiffness matrix in truss analysis.
- You must always create a stable Strut-and-Tie Model; Stabilizers are identified by CAST during truss analysis.
- See Q & A #4 for more detail about Stabilizers.
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