This tutorial explains how horizontal and vertical layout line geometry can be defined in SAP2000. The layout line is broken into a number of segments between the transition points (PT - point of tangent, PC - point for curvature, PVT - point of vertical tangent, PVC - point of vertical curvature) and each segment is defined using the parameters available in the relevant SAP2000 form.

Baseline Geometry

A sample baseline to be entered into SAP2000 is described in the following two sections.

Horizontal Profile

Vertical Profile

Data to be entered to SAP2000

Each row in the SAP2000 table below is used to define one segment of the horizontal alignment as follows:

• The first row indicates that the initial bearing is N 90° 0′ 0″ E.
• The 2nd row defines straight segment, 100m long at the previous bearing, ie. N 90° 0′ 0″ E.
• The 3rd row defines the first curved segment. For our alignment, there are no transition curves as the entire second segment has a constant radius of 100m. Therefore, we need to enter the end bearing such that it exactly corresponds to the final station for the segment. In general, either the radius or the end bearing is sufficient to define a circular curve with constant radius. If you specify radius and end bearing that do not represent a circular segment with constant curvature, then an arc of the specified constant is 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.
• The description of the next three rows is similar to the previous rows.

Each row in the SAP2000 table below is used to define one segment of the vertical alignment as follows:

• The first row lists initial elevation and initial grade as entered on the "Bridge Layout Line Data" form.
• The 2nd row defines constant slope (20% segment) up to station 100.
• The 3rd row defines parabolic segment with initial slope +20% and end slope -20%.
• Finally, the 4th row defines constant slope (-20% segment) up to station 614.16.