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*Lanes* canmay be *defined using one of the following two approaches:

* from frame elements
* from* according to either *layout-line* or *frame-object* geometry.


h2. Lane definition using layout lines

When [layout lines|layoutkb:Layout line] 
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h1. Lanes defined from frames

For lanes defined from frame elements, the moving load is applied directly to the frame elements that were used to define the lane. This true for zero-width lanes as well as nonzero-width lanes. If the lane was defined with an eccentricity relative to the frame element, the program accounts for this eccentricity by applying torsional moment that is equal to the moving load times the eccentricity, as described in more detail in the following section.

h2. Eccentric load applied to lanes defined from frames

When an eccentric vertical load is applied to a lane defined from frame elements, SAP2000 will apply this eccentric load directly to the frame element that was used to defined the lane using the vertical load and torsional moment (to account for the eccentricity) as follows:

* The vertical load is applied at the centerline of the frame element at the location that corresponds to the intersection of the frame centerline and a line perpendicular to this centerline and passing through the location of the eccentric load.
* Torsional moment is calculated as a product of the vertical load magnitude and its transverse eccentricity from the centerline of the frame. This torsional load is applied at the same location as the vertical load described above.

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Related incidents and emails:

define [lane|kb:Lane] geometry, vehicle loading is applied through to the following process:

* The lane is [discretized|kb:Lane discretization] according to lane-definition parameters and plan-view locations where layout lines intersect structural-object edges.

* [Lane-load points|kb:Lane-load point] are created along and across each lane relative to this discretization

* A gravity-direction unit load is applied to each lane-load point to determine the normalized deflected shape

* [Lane-to-object connections|kb:Lane-to-object connection], which redistribute tributary lane loading to the [joints|kb:Joint] of structural objects, are created in the transverse direction from each lane-load point. Connection geometry may be reviewed, and if necessary, edited through Display > Show Lanes > Show Structural Connection For Selected Point.

* Vehicle load which is applied during analysis may then transfer from traffic lanes to the superstructure.


h2. Lane definition using frame objects

When lane geometry is defined according to [frame|kb:Frame] objects, vehicle load is applied directly to those frames. This is the case for both zero-width and nonzero-width lanes. When an eccentricity exists between the lane load and the frame, an equivalent torsional moment is applied to the frame object. Please note that the vertical component is also applied in this location, transverse from the position of the vehicle load within the lane.


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*Related incident and email:*
* {incident:no=30603|comment=Applying eccentric loads to lanes defined from frames} \\
* {email:date=12/27/2010|from=ok|to=me|subject=Applying eccentric loads to lanes defined from frames|comment=Description of the procedure|id=6357715}
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h1. Lanes defined from layout lines

For lanes defined from layout lines, the program uses the concept of [lane loading points|Lane-load point] and [structural connections|Lane-to-object connection] as follows: Based on the lane discretization, the program creates lane loading points along the width and length of each lane in the model. Then it places unit load in gravity direction at each lane loading point to determine the deflected shape. The unit load applied to the lane loading point is proportionally distributed to the tributary joints in the model. Using "Display > Show Lanes > Show Structural Connection For Selected Point" you can display the connections between the lane loading point and the joints in the model. Lanes defined from layout lines were available up to SAP2000 V14 and required the bridge license. They are no longer available in SAP2000 V15, because they were "moved" to the CSiBridge program, which is essentially the successor of the bridge modeler in SAP2000.