Double Corbel Design using CAST (Part 2)

 

 In the above figure, STM shape that is adopted for design the double corbel is shown. To illustrate in more details all components of this STM constructed by CAST, the following info is provided 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.
  
  
  
  
  After you are familiar with all components given above, it is time to show you steps by steps how to construct STM using CAST. Please follow the instruction in the next post. For the previous post about designing of double corbel using CAST (part1) please see here.