Lanes may be defined according to either layout-line or frame-object geometry.

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Lane definition using layout lines

When layout lines define lane geometry, vehicle loading is applied through to the following process:

• The lane is discretized according to lane-definition parameters and plan-view locations where layout lines intersect structural-object edges.

• Lane-load points 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, which redistribute tributary lane loading to the joints 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.

Lane definition using frame objects

When lane geometry is defined according to 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.