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Coordinate systems utilized for FEA results can be summarized as follows:
Node Displacements (Local):
Node displacements are presented with respect to the node's associated coordinate system. Typically, for most bridge workflows, nodes follow the alignment coordinate system. However, for bearing nodes, if the bearing rotation is defined, this parameter will directly affect the node's coordinate system by rotating the axes according to the bearing rotation definition.
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Node Reactions (Local):
Node reactions are presented to the user based on the node's local coordinate system. In most cases, this coordinate system aligns with the alignment coordinate system. However, if the bearing rotation parameter is defined with a value other than zero, the node's coordinate system will rotate accordingly, and the reactions will follow the updated orientation.
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Force X: Represents the longitudinal alignment direction.
Positive values: Indicate forces resisting movement in the downstation direction.
Negative values: Indicate forces resisting movement in the upstation direction.
Force Y: Represents the transverse direction, perpendicular to the alignment.
Positive values: Indicate forces resisting movement to the left when looking upstation.
Negative values: Indicate forces resisting movement to the right when looking upstation.
Force Z: Represents the vertical direction.
Positive values: Indicate forces resisting downward movement, often corresponding to compressive reactions.
Negative values: Indicate forces resisting upward movement, often corresponding to uplift or tension.
Node Reactions (Global):
Node reactions in this section are presented to the user with respect to the global coordinate system.
Element End Forces (External - Local):
The forces at the ends of each FELine and FESurface are presented to the user in this section with respect to the element's local coordinate system.
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If the user intends to use these forces or Element End Forces (External - Global) for design purposes, they should exercise caution, as the sign convention for element end forces is opposite with respect to the element's local coordinate system. For example, a positive axial force at one end of the element will appear as a negative axial force at the opposite end. This reversal is inherent to how forces are represented and must be accounted for during the design process to avoid errors. Alternatively, using FELine internal forces may provide a simpler approach. |
Element End Forces (External - Global):
The forces at the ends of each FELine and FESurface generated are presented to the user with respect to the global coordinate system in this section.
Composite Element Forces (Sectional):
FEComposite forces represent the combined effects of internal forces across multiple finite elements that make up a composite structure or a group of connected elements.
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Fx (Axial Force): Represents the force along the girder's longitudinal axis. For example, a positive Fx indicates tensile forces, while a negative Fx indicates compressive forces.
Fy (Shear Force in the Y-Direction): Represents the transverse shear force acting perpendicular to the girder's length.
Fz (Shear Force in the Z-Direction): Represents the vertical shear force acting in the vertical plane of the girder.
Mx (Torsional Moment): Represents twisting along the girder's axis.
My (Bending Moment about the Y-Axis): Represents major-axis bending, typically caused by vertical loads.
Mz (Bending Moment about the Z-Axis): Represents minor-axis bending, typically caused by lateral forces.
FELine Forces (Internal):
FELine internal forces are displayed in this section along the local axes of the FELine element. These forces include axial, shear, and bending components:
Force X: Represents the axial force within the element. Negative values indicate compression, while positive values indicate tension.
Force Y: Represents the shear force in the local Y-axis direction, perpendicular to the element's axis.
Force Z: Represents the shear force in the local Z-axis direction, also perpendicular to the element's axis.
Moment X: Represents the torsional moment about the local X-axis.
Moment Y: Represents the bending moment about the local Y-axis, where positive and negative values indicate different bending directions.
Moment Z: Represents the bending moment about the local Z-axis, following the same convention as Moment Y.
FELine Stresses:
Stresses calculated for FELines can be viewed under this section.
FESpring Forces (Global):
The spring forces at each node are displayed in this section. The results for each node are reported based on the node's coordinate system, which, in most cases, aligns with the alignment coordinate system.
In a typical bridge workflow, if the bearing rotation angle is 0:
X-axis: Represents the longitudinal direction of the alignment.
Positive values: Indicate forces acting in the upstation direction.
Negative values: Indicate forces acting in the downstation direction.
Y-axis: Represents the transverse direction, perpendicular to the alignment.
Positive values: Indicate forces acting to the left when looking upstation.
Negative values: Indicate forces acting to the right when looking upstation.
Z-axis: Represents the vertical direction.
Positive values: Indicate upward forces.
Negative values: Indicate downward forces, often corresponding to compressive reactions.
FESurface Forces (Internal):
Composite Element Stresses:
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