| Info |
|---|
This page is devoted to frequently asked questions (FAQ) related to hinges. |
Default hinge properties are derived from which source?
...
Answer: The yield rotation of a hinge is calculated as yielding curvature (My/EI) multiplied by hinge length.
For the automatic FEMA frame hinges, the yield rotation is specified in the code (ASCE 41-06, Table 5-6) as the chord rotation of the full member length due to plastic moment at one end. Specifically, the yield rotation is Mp/(6*E*I/L), where Mp = Z*fy, and L is the frame object (not element) length and this is how the yield rotation is determined in the program.
Why do hinge results deviate from the defined hinge backbone?
...
- A sufficient number of multiple states should be specified on the Results Saved for Nonlinear Load Cases menu when running nonlinear static analysis.
Strength loss (degradation), indicated by the negative slope of a backbone curve, is automatically limited to 10% of the frame-element elastic stiffness. Rationale is explained in the
Analysis Reference Manual (Strength Loss, page 135). A hinge-overwrite option is available through the Assign > Frame > Hinge Overwrites menu such that users may specify steeper strength degradation by using a small relative length on the order of 0.02.
- The backbone curve for a coupled hinge is only valid if the yield point on the interaction surface does not change. This may occur with P-M2-M3 hinges, for example, when P or M3 change, causing M2 to deviate from the backbone curve. Please keep in mind that the backbone curve represents a triaxial relationship between each of these parameters. See test problem Hinge response when yield point changes for an example.
...
Answer: For response, please see the
Analysis Reference Manual (Scaling the Curve, page 135).
...