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This page is devoted to frequently asked questions (FAQ) related to links. |
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Modeling
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Answer: The only difference which results from changing link length is an additional moment which results from shear acting over the increased length. Likewise, the specification of length location for shear deformation may change link response because this parameter correlates with internal link deformation. Please note that link deformation occurs at a single location specified on the Link Definition menu by the value Shear Distance from End J. The equations used to calculate link deformation are available in the CSI Analysis Reference Manual (The Link/Support Element > Section Internal Deformations, page 238). Changing link length does not affect link stiffness since this value is based on the total force or moment.
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Use engineering judgement when deciding upon linear and nonlinear stiffness properties.
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| *Related Incident:* * {incident:no=48467|comment=ETABS/ SAP - partial fixity- (Coefficient of friction)} |
Formulation
What are the Link Directional Properties?
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- Leave the Direction option unchecked, as shown in Figure 1 with U1. This will keep the link from contributing stiffness to the direction specified.
- Select the Direction and Fixed option, as shown with U2. In this case, the link will not experience any deformation in the direction specified because relatively large stiffness will be applied to that component.
- Select the Direction and Nonlinear option, as shown with U3. Here, the link will contribute the stiffness specified when Modify/Show is selected from below the Properties heading.
Figure 1 - Link directional properties
How is link stiffness calculated?
Answer: For the various link objects available, force-deformation relationships may be defined along each degree-of-freedom (DOF), including axial, torsional, major and minor shear, and major and minor bending. These properties may be specified to simulate the behavior desired of bearings, isolators, soil springs, and other structural components modeled using link objects.
The CSI Analysis Reference Manual (The Link/Support Element - Basic > Internal Deformations and Link/Support Properties, pages 238 and 240) provides additional details on force-deformation relationships and internal link deformation and forces. The Derivation of link equations article may also be useful.
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