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This page is devoted containsto *frequently asked questions* (FAQ) related to *[links|kb:linkLink]*.
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h1. General FAQ

{anchor:changing-length}

h2. Does changing thelink length ofaffect theresults?
link
element have impact on the results?

Changing the length of a [link element|Link] has no effect on the stiffness values, since they are based on the total force or moment. The only effect is the generation of a moment due *Answer:* The only difference which results from changing [link|kb:Link] length is an additional moment which results from shear acting over the increased length. Likewise, changingthe specification theof length location of thefor shear deformation (defined by specifying a distance from J end) may change thelink response asbecause this parameter has impact on thecorrelates with internal link deformationsdeformation. Please note that the link deformationsdeformation occuroccurs at a single location specified on the Link Definition menu by the "value Shear Distance from End J" on the. The equations used to calculate link definitiondeformation form.are Pleaseavailable refer toin the {new-tab-link:http://www.csiberkeley.com/}CSI{new-tab-link} [_Analysis Reference Manual_|doc:CSI Analysis Reference Manual] (The Link/Support Element > Section Internal Deformations, page 238). forChanging thelink equationslength useddoes tonot calculateaffect link deformations. stiffness since this value is based on the total force or moment.


h2. Which link property is the most suitable for tomodeling modelreinforced-concrete shear behavior?
of
reinforced concrete?

Multi*Answer:* The multi-linear plastic -link property, with pivot hysteresis type, would be most suitedsuitable tofor modelmodeling the shear behavior of reinforced -concrete members.


h2. Should I use a hinge or a link?

_See_ _["Comparison of hinges and links"|*Answer:* For response, please see the [Hinge and link comparison|kb:Hinge and link comparison]_ _pagearticle._


h2. What are the Link Directional Properties?

There*Answer:* Three options are theavailable when followingdefining threeLink mainDirectional optionsProperties. whenTheir youdescriptions defineare linkgiven directionalas propertiesfollows:

*# You leaveLeave the Direction option unchecked, (as shown isin theFigure case1 forwith U1. inThis thewill screenshot below) - then keep the link will not contribute anyfrom contributing stiffness forto the givendirection directionspecified.
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You# checkSelect the Direction and Fixed option, (as isshown the casewith for U2. in the screenshot below) - in In this case, the link will not experience any deformation in the given direction. Inspecified otherbecause words,[relatively it will behave as being infinitely stiff for the given direction.

* You check Direction and NonLinear (as shown for U3 in the screenshot below) - thenlarge stiffness|kb:Rigid behavior] will be applied to that component.
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# Select the Direction and Nonlinear option, as shown with U3. Here, the link will contribute the stiffness specified when you click the "Modify/Show ..." buttonis selected from below the Properties heading.

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!Link_directional_properties.png|align=center,border=0!

{center-text}Figure 1 - Link directional properties{center-text}


h2. How should I calculate theis link stiffness valuescalculated?

*Answer:* ThereFor arethe various types of links[link|kb:Link] objects available, inforce-deformation therelationships programmay andbe youdefined canalong define their force deformation relationship (for axialeach degree-of-freedom (DOF), including axial, torsional, major and minor shear, torsion,and major and minor purebending. bendingThese DOFs)properties tomay representbe thespecified behaviorto ofsimulate the structuralbehavior componentdesired (such as bearingof bearings, isolatorisolators, soil springsprings, etc.)and thatother isstructural beingcomponents modeled by the link.

Please review using link objects.

The {new-tab-link:http://www.csiberkeley.com/}CSI{new-tab-link} [_Analysis Reference Manual_|doc:CSI Analysis Reference Manual,] chapter "(The Link/Support Element - Basic", sections> "Internal Deformations" _and_ "Link/Support Properties" for, pages 238 _and_ 240) provides additional details on link internal deformations, force-deformation relationshiprelationships and internal link deformation internaland forces. The You[Derivation mayof also find it useful to review the [link equations|doc:Derivation of link equations] page. article may also be useful.


h2. How can I plot force-displacement hysteresis curve for isolatorisolators?

*Extended QuestionAnswer:* HowFor do I get output force-displacement hysteresis curve for isolator? I was trying to see under Display/Show plot function but I couldn’t figure it out force vs. displacement only I found time vs. displacement.

*Answer:* _[See plotting link hysteresis curve page.|response, please see the [Plotting link hysteresis|kb:Plotting link hysteresis]_ article.


h2. What are the units for link effective damping?

*Answer:* For all link properties, the damping input is the actual damping, given in units of Force-SecSecond/Length, (i.e.or Force/Velocity).