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h1. Overview

When [line spring|kb:line spring] or [area springs|kb:area spring] are assigned to an object, SAP2000 automatically[SAP2000|sap2000:home] generates equivalent [joint|kb:Joint] springs at each jointnode created bythrough [automeshingauto-meshing|kb:automeshing] of such objectDiscretization]. Stiffness of these joint springs Joint-spring stiffness is determined from thetributary stiffnessarea ofand the line- or area-spring springstiffness assigned to the object and the tributary area for each joint spring (joint . Joint springs supporting interior joints are stiffer than the joint springsthose supporting corner joints). Since the contact pressure wouldis be proportional to thejoint-spring deformation of these joint springs or toand the displacement of joints to which these joint springs are attached, youusers canmay obtain the contact pressure through bythe product multiplyingof thespring-stiffness displacementsconstant (thatand candisplacement, bewhich readilyis output both graphically and in a tabular format) by a constant related to the spring stiffness.

h1. Example model

AnThe example model that illustrates the above has been , attached tofor this page.

The example model reference, contains 2two [area|kb:Shell] objects (2m byx 2m and 1m byx 1m), each auto -meshed into 4four area objects), 2two [frame|kb:Frame] objects (2m long and 1m long), each auto -meshed into 2two frame objects), and 1one [point|kb:Joint] object. A [link|kb:Link] with property (LIN1) is assigned as area spring to the area objects, as an linearea spring, to the frame objects and alsoas a line spring, and to the point object. as Thea stiffnessjoint oflink. theLink LIN1stiffness wasis defined as follows:

* 1kN/m when used as a joint link

* 1kN/m/m when used as a line spring

* 1kN/m/m^2 when used as an area spring

The "Factors For Line, Area, and Solid Springs", available on the "Link/Support Property Data" formmenu, are explained in theFigure 1:
figure
below:\\

!Link_and_support_property_data.png!

A|align=center,border=0!

{center-text}Figure 1 - Link and support property data{center-text}

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The SPRING-LOAD [load case|kb:Load case] applies a unit load to objects, including (1kN/m^2 for the area objects, 1kN/m for the frame objects, and 1kN for the point object) was applied to the objects in the SPRING-LOAD load case. Reviewing the UZ displacements for the "SPRING-LOAD" load case indicates that the displacements displacement of 1m at all the joints areindicates consistentconsistency withbetween the applied loadsloading and stiffness assigned tostiffness.
the
areaThe and line springs.

Stiffness of thestiffness of automatically-created internal springs created by the program could be indirectly determined by dividing ajoint reaction for a particular joint by its displacement. The joint reactions and displacementsThese values are available in the output tables., Thewhere internally created joints are preceded by a "~"tilda symbol (tilda~).
symbol.

h2. ScreenshotsModel of thescreenshots model and results

h3. Area -spring and auto -mesh assignment
to
an\\
area
object

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

{center-text}Figure 2 - Area-spring and auto-mesh assignment{center-text}


h3. DisplayEquivalent joint springs
of
equivalentThe jointsoftware springsautomatically createdcreates byequivalent thejoint programsprings towhich represent those line and area springs which are assigned to an object. These joint springs are displayed Usingthrough "View > Set Display Options > Show Analysis Model" menu command, youas canshown displayin theFigures equivalent3 jointand springs4:
created
by the\\
program
for an area spring → !Show_Analysis_Model_Form.png|align=center,border=0!

{center-text}Figure 3 - Show analysis model{center-text}

\\

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

{center-text}Figure 4 - Equivalent joint springs{center-text}


h1. Attachments

* [SAP2000 V12.0.0 model file|^springs line and area V12.0.0.zip] (Zippedzipped SDB file)