Layout line FAQ
- Mike Abell (Unlicensed)
- Ondrej
- Jessica Napier (Unlicensed)
This page is devoted to frequently asked questions (FAQ) related to bridge layout lines.
On this page:
How is the radius of a curved layout line measured?
Extended Question: For a definition of curved layout line segment, both radius and end bearing need to be entered along with the end station. What type of curve is being defined by this? For a true circular segment, either radius or end bearing would be sufficient. What curve is being defined and where is the radius measured?
Answer: Spirals are automatically and internally created by the program when the radius and end bearing for a layout line segment are entered such that the radius is smaller than would be a radius for true circular segment whose end tangents match the tangents of adjacent layout line segments.
An arc of specified constant radius is then centered within the specified station range. If this arc length is less than the difference in stations, transitions are created of where the curvature varies linearly from 1/R at each end of the arc to zero at the corresponding station end point.
How is layout-line elevation specified?
Extended Question: For superstructure surfaces which are not level, such as a straight deck with center crown and outward slope, where should I specify the layout-line elevation?
Answer: Layout-line elevation should be specified above the riding surface elevation such that lane load may project downward to the joints immediately below the lane elevation. Once the layout line is defined, users may ensure that loading is correct through the Display > Show Lanes > Show All Points and Connections menu. The lane loading article presents additional details.
If lane loading points connect to joints further below the riding surface, restriction may be placed on objects subjected to loading using the Objects Loaded by Lane option on the Lane Definition form.
How are straight girders placed along layout lines which curve in a horizontal plane?
Answer: Since the bridge section remains constant, and the deck curves within a horizontal plane, the bridge modeler makes cuts orthogonal to the curved layout line, then defines girders as linear segments between cuts.