Bottom Flange Access Hole Model [STG]
- Melis Ceylan
The first step in performing Access Hole-related checks is to define and generate the access hole within a separate Steel Tub Girder project. As outlined in the Access Hole Design (STG), the analysis of access holes requires a refined mesh to ensure the Finite Element Analysis (FEA) is as accurate as possible.
To maintain the simplicity and efficiency of the global bridge model, this separate project approach is the recommended method for modeling access holes.
Applying Loads and Analyzing Access Holes in Steel Tub Girders
Following the modeling step, the next phase involves applying the relevant loads, such as axial loads, to the access hole. This is done using the Bottom Flange Access Hole Load object.
For detailed instructions on applying these loads, refer to the Bottom Flange Access Hole Load section in the documentation. This process ensures loads are applied accurately and consistently within the refined model.
After performing the analysis, the stress concentrations and corresponding values can be displayed, providing a clear understanding of the localized effects caused by the access hole.
General
The geometric properties of the access hole model for both 3D and FEM can be defined using the parameters on the General Tab.
Plate Length: The plate length (in the X-axis direction on the global coordinate system) can be defined using this parameter.
Plate Width: The plate width (in the Y-axis direction on the global coordinate system) can be defined using this parameter.
Plate Thickness: The thickness of the plate (in the Z-axis direction on the global coordinate system) can be defined using this parameter.
Hole Diameter: The diameter of the hole can be defined using this parameter.
Plate Material: A material must be assigned to the access hole plate. Materials can either be imported or assigned from previously defined ones under Properties > Materials. The material properties will be directly used for FEA (Finite Element Analysis).
Mesh Size: The mesh size definition is the maximum distance between two adjacent nodes. A larger mesh size results in a less refined FEM model.
Circle Segment: This parameter specifies the number of segments used to generate circle of the access hole. A larger number for the circular segment would generate a smoother circle.
Mesh Option: The generation of a mesh for FEM of the plate can be specified by this parameter.
MeshAdapt : Adapts the mesh during the simulation based on solution gradients for improved accuracy.
Automatic : Generates a mesh automatically with default settings, providing quick and simple results.
Initial Mesh Only : Generates only an initial mesh without further refinement or adaptation.
Delaunay : Uses Delaunay triangulation to create high-quality triangular (2D) or tetrahedral (3D) meshes for complex geometries.
Frontal-Delaunay : A variant of Delaunay that constructs the mesh incrementally using front-tracking for better element quality.
BAMG : A mesh generation method optimized for handling complex geometries, often with minimal user input.
Frontal-Delaunay for Quads : Applies the frontal Delaunay method specifically for quadrilateral meshes, often in 2D.
Packing of Parallelograms : Fills the domain with parallelogram-shaped elements, suitable for structured meshes.
Quasi-structured Quad : Generates a mostly structured quadrilateral mesh with some flexibility for irregular shapes.
Left Edge Boundary Conditions
For the left edge of the plate, the stiffness values to be applied to the nodes for translation along the axes Tx, Ty, Tz, and rotation along the axes Rx, Ry, Rz can be specified using the parameters in this tab. The stiffness values can be defined as either Free or Fixed, or by specifying values.
Tx [Free/Fixed]: Translation along the X-axis direction
Ty [Free/Fixed]: Translation along the Y-axis direction
Tz [Free/Fixed]: Translation along the Z-axis direction
Rx [Free/Fixed]: Rotation about the X-axis direction
Ry [Free/Fixed]: Rotation about the Y-axis direction
Rz [Free/Fixed]: Rotation about the Z-axis direction
Right Edge Boundary Conditions
For the right edge of the plate, the stiffness values to be applied to the nodes for translation along the axes Tx, Ty, Tz, and rotation along the axes Rx, Ry, Rz can be specified using the parameters in this tab. The stiffness values can be defined as either Free or Fixed, or by specifying values.
Tx [Free/Fixed]: Translation along the X-axis direction
Ty [Free/Fixed]: Translation along the Y-axis direction
Tz [Free/Fixed]: Translation along the Z-axis direction
Rx [Free/Fixed]: Rotation about the X-axis direction
Ry [Free/Fixed]: Rotation about the Y-axis direction
Rz [Free/Fixed]: Rotation about the Z-axis direction
Top Edge Boundary Conditions
For the top edge of the plate, the stiffness values to be applied to the nodes for translation along the axes Tx, Ty, Tz, and rotation along the axes Rx, Ry, Rz can be specified using the parameters in this tab. The stiffness values can be defined as either Free or Fixed, or by specifying values.
Tx [Free/Fixed]: Translation along the X-axis direction
Ty [Free/Fixed]: Translation along the Y-axis direction
Tz [Free/Fixed]: Translation along the Z-axis direction
Rx [Free/Fixed]: Rotation about the X-axis direction
Ry [Free/Fixed]: Rotation about the Y-axis direction
Rz [Free/Fixed]: Rotation about the Z-axis direction
Bottom Edge Boundary Conditions
For the bottom edge of the plate, the stiffness values to be applied to the nodes for translation along the axes Tx, Ty, Tz, and rotation along the axes Rx, Ry, Rz can be specified using the parameters in this tab. The stiffness values can be defined as either Free or Fixed, or by specifying values.
Tx [Free/Fixed]: Translation along the X-axis direction
Ty [Free/Fixed]: Translation along the Y-axis direction
Tz [Free/Fixed]: Translation along the Z-axis direction
Rx [Free/Fixed]: Rotation about the X-axis direction
Ry [Free/Fixed]: Rotation about the Y-axis direction
Rz [Free/Fixed]: Rotation about the Z-axis direction