Paths

Paths define traffic lines along a bridge related to the alignments. These can be for trains, road vehicle or pedestrians. Different path types are used for the different ways of using the tools available for bridge loading described in Step-by-Step guide to Bridge Loading.

For highway loading, if a design code has been specified in the Bridge Loading Analysis Specification dialogue then the full width of a carriageway between kerbs is entered (the notional width for HK carriageways without raised kerbs), along with any footways, and the programme will automatically divide this into lanes and vehicle paths for analysis. In all other cases the user must specify Lanes individually, plus Vehicle paths if vehicles are not to be placed central in Lanes.

Paths must be defined before carrying out an Influence Analysis, or using the Bridge Loading table to set up load cases, and can be used to position vehicles in the Generate Vehicle dialog. Paths are used in conjunction with an alignment to define the road or railway track geometry.

Definition

Path Name

The name of the path will be used in the Bridge Loading table and the Generate Static Vehicle dialog to identify the path.

Path Type

The deck section is split up into paths. The paths can be of the following types:

• Lane – for roads where automatic path generation is not available.
• Footway – for pedestrians.
• Track – for railways.
• Vehicle – to define a vehicle path straddling lanes, or to place vehicles off centre within a lane, where automatic path generation is not available.
• Carriageway 1 way – for roads where automatic lane generation is available, carrying 1 way traffic, minimum width 5m.
• Carriageway 2 way – for roads where automatic lane generation is available, carrying 2 way traffic, minimum width 5m.

No checks are made on whether Footway and Lane paths overlap, but a severe warning is given if Footway and Carriageways defined from a single alignment overlap. In this case (or if there are overlaps between carriageways defined from different alignments, which are not identified by the program) the user will need to review the Static Bridge Loads and delete any overlapping loads. Any gaps between lanes will be considered as central reserves and left unloaded.

Path Group

Group number is only used by the program in automatic path generation.

The deck can be considered as a series of groups of paths. Thus a two lane dual carriageway consisting of six paths could be considered as four groups – two carriageway groups (each containing two paths), and two footway groups. The central reserve is formed by the gap between the central lanes. Vehicle paths should be given the same group number as the lanes they straddle.

Alignment

The Alignment which this path follows. For highways this will normally be the same for all paths.

Offsets / Gauge

The values entered here define different things depending on the path type.

For footways and lanes: offsets from the Alignment to the left and right sides of the path. Vehicles will always be placed centrally in the path.

For tracks: offset to the centreline of the track, and track gauge (rail spacing, standard gauge – 1.435m).

For vehicle path: offset to centreline of vehicle.

A positive offset is to the right when looking along the alignment.

Left Rail Factor

When the path type is track it is possible to specify how the load will be split between the left and right rails by specifying the percentage of the load taken on the left rail.

Number of Marked Lanes

The number of marked lanes on a 1 way or 2 way carriageway. Use for CS454 assessment only.