Bridge Linear Structures (2D)

Bridge Linear Structure (2D) objects are used to define bridge dimensions, coefficients and the location of bridges within 2D Base Linear Structures.

See Bridge Linear Structure (2D) Data Fields for more information on data required to define a 2D bridge.

Bridge Linear Structure (2D) parameters are edited in the Bridge Linear Structure (2D) Grid Window of the Lines Grid or the Bridge Linear Structure (2D) Property Sheet.

2D bridge can be created in the Lines Grid or digitised directly on the GeoPlan Window as line objects, although it is not necessary to digitise the objects as they will assume the length geometry of the referenced 2D base linear structure.

Associating bridges with linear structures

To associate a 2D bridge with a 2D base linear structure, specify the base linear structure in the Base linear structure (2D) ID field.

The starting location of the bridge is defined by the bridge Start length field, which is the length along the referenced base linear structure relative to its starting point. The geometry of the base linear structure will be applied to the 2D bridge along the length of the bridge.

If the bridge has already been digitised on the GeoPlan, it will be redrawn overlaying the referenced 2D base linear structure line.

Note that if a 2D bridge is associated with a 2D base linear structure, the polyline representing the bridge geometry cannot be edited in the GeoPlan Window. The horizontal geometry of the bridge is controlled by the geometry of the base linear structure.

2D bridges are displayed in the 3D Network Window and in the section editor of the 2D base linear structure. These views can be used to check that the location of bridge objects has been defined correctly.

Flow characteristics

Flow through a 2D bridge opening is calculated on an element face by face basis using the same flow equations described in the Sluice Gates topic for 1D sluices.

The Base Linear Structures (2D) topic contains details of how any blockage, lateral friction coefficient and headloss coefficients are applied by the engine.

Sampling elevations from a ground model

Bridge linear structure invert level data can be updated by sampling a Ground Model. Elevations at existing vertices can be updated and new vertices inserted between existing vertices.

Only bridge linear structures with Invert level set to Irregular can be updated. If vertices are inserted between existing vertices, Opening height and Deck thickness values will be calculated by linear interpolation.

See Updating Network Objects from the Ground Model for details.

 

Results

Flow crossing the linear structure is monitored and output in the Line Results. The flow direction is determined using the same convention used for river sections, in which the first point on the line structure is assumed to be on the left hand side when facing downstream.