Hinge Property [SIG]
Hinges represent points in the structural model where plastic deformation is expected to occur under seismic loads. They are essential for nonlinear pushover analysis to capture the inelastic behavior of pier columns. It can be assigned to columns as shown below, at both the top and bottom locations.
Nonlinear
Hinge Stiffness Option [From Report/User Input]: The user can define how the hinge stiffness is determined:
From Report: The hinge stiffness is automatically derived from the Moment-Curvature Report.
User Input: The user directly specifies hinge stiffness values for each axial force.
Moment Curvature Report: If "From Report" is selected in the Hinge Stiffness Option, you can assign a Moment Curvature Report to automatically derive hinge stiffness parameters. Follow these steps:
First, create and configure a Moment-Curvature Report with appropriate section geometry, materials, and axial forces.
In the Moment-Curvature Report, go to the Output tab and use the "Compute" cell action to generate the analysis results.
Return to this Hinge Property and select the computed Moment Curvature Report from the dropdown in this parameter.
The hinge stiffness values (Ry and Rz) will be automatically extracted from the report for all specified axial force levels.
The Moment-Curvature Report must have its output computed before it can be assigned here. If the report is not computed, the hinge will not have valid stiffness data and analysis may fail. See Moment-Curvature Report - Output Tab for instructions on computing the report.
Hinge Stiffness: If the user selects the option ‘Set to User Input’ in the ‘Hinge Stiffness Option’ column, further definitions can be made using the ‘Hinge Stiffness’ column's ‘Edit…’ option, detailed by Axial Force/Fixity (Ry)/Fixity (Rz). When defining hinge stiffness data, make sure to include a sufficient number of axial force data points around the expected dead load level.
Define hinge stiffness data with enough axial force points around the expected dead load for stable nonlinear convergence.
Use intervals of about 50 kips near the maximum load.
Example: For a –750 kip dead load, enter values such as 250, 0, –50, –100, … –1000 kips.
Positive values indicate tension, and negative values indicate compression - both are required for accurate nonlinear analysis.
Linear
The linear stiffness properties define the hinge behavior for translations and rotations that are not controlled by the nonlinear moment-curvature response. These parameters control the elastic behavior in directions where plastic deformation is not expected.
Tx [Fixed/Stiffness]: Controls the translational stiffness along the local X-axis of the hinge.
Fixed: Select this option to fully restrain translation in the X-direction. The hinge will not allow any displacement along the X-axis.
Stiffness: Enter a numerical spring stiffness value (Force/Length units) to allow elastic displacement in the X-direction. Higher values indicate stiffer springs with less displacement.
Ty [Fixed/Stiffness]: Controls the translational stiffness along the local Y-axis of the hinge.
Fixed: Select this option to fully restrain translation in the Y-direction. The hinge will not allow any displacement along the Y-axis.
Stiffness: Enter a numerical spring stiffness value (Force/Length units) to allow elastic displacement in the Y-direction. Higher values indicate stiffer springs with less displacement.
Tz [Fixed/Stiffness]: Controls the translational stiffness along the local Z-axis of the hinge.
Fixed: Select this option to fully restrain translation in the Z-direction. The hinge will not allow any displacement along the Z-axis.
Stiffness: Enter a numerical spring stiffness value (Force/Length units) to allow elastic displacement in the Z-direction. Higher values indicate stiffer springs with less displacement.
Rx [Fixed/Stiffness]: Controls the rotational stiffness about the local X-axis of the hinge (torsion).
Fixed: Select this option to fully restrain rotation about the X-axis. The hinge will not allow any torsional rotation.
Stiffness: Enter a numerical rotational spring stiffness value (Moment/Angle units) to allow elastic rotation about the X-axis. Higher values indicate stiffer torsional springs with less rotation.
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