Oasys GSA Documentation

# Static Bridge Load

This table allows the user to define static bridge loads. To apply these loads to the structure they have to be expanded to Grid Point Loads using the “Model | Bridge Modelling | Expand Bridge Loading” menu command.

All bridge loading defined in this table is defined relative to paths specified in the Paths table. Single vehicle load cases can also be defined in the “Generate Static Vehicle” dialog from the “Model | Bridge Modelling | Generate Static Vehicle Load” menu command. Note that once the load cases have been generated changes to this table or the data to which it refers will not affect the generated load.

# Definition

Name, Group

Each Group forms a single load case when expanded into grid point loads, with Name from first line in group used as the load case title.

Path

The path name to be loaded. A number of restrictions apply to combinations of path and load types:

Vehicle paths can only be loaded with vehicles.

Footway paths can only be loaded with KEL or UDL loads (to place accidental wheel loads on footways use the Generate Static Vehicle dialog.)

Lane and Track paths can accept any loading.

If "Bridge design loading code" is selected in "Bridge Loading Specification", the bridge analysis has to be done first, then the carriageways paths can be populated to the path dropdown list and the static bridge loads can be defined and expanded.

Load Type

This can be one of the following:

  • Static vehicle – standard vehicle from the list below, or a vehicle defined in the Vehicle table, placed centrally in the path with the datum (normally the centre of the rear axle) at the chainage specified. A single grid point load will be generated for each wheel of the vehicle. The magnitude of the wheel loads can be factored (for example the standard 45 unit HB vehicle can be factored to represent smaller vehicles). Note that vehicles can also be positioned in space and wheel loads represented by patches rather than point loads using the Generate Static Vehicle dialog.
  • Static KEL – a series of six grid point loads (or two point loads for tracks) will be generated to simulate a line load, equally spaced across the width of the path at the chainage specified. The intensity of the KEL is the total line load. The KEL will always be placed normal to the alignment. To place a KEL at a skew the Grid Point loads will need to be modified after expansion.
  • Static UDL – a series of grid point loads will be generated to simulate a UDL over the full width of the path. Lines of six point loads (or two point loads for tracks) equally spaced across the path at regular intervals will be generated in a single load case (combined with any other static loads with the same bridge case number). The intensity of the UDL is defined per unit length of the path, not per unit area.

Start and End Chainage

Define first and last positions of the UDL on the path.

Vehicle

Selected from the standard and user defined vehicles.

Load Intensity / Load Factor

Multiplier on vehicle wheel loads.

Magnitude of KEL (positive).

Magnitude of UDL (positive) per unit length (not per unit area) along the alignment. Note that with large offsets on curved alignments the intensity per metre of path will not correspond exactly to this value.

Effect, Group Total Effect

Effect is given where the static bridge load has been derived by the Optimiser. The effect is the magnitude (in SI units) of the effect being optimised resulting from the current line of static bridge loading, derived from the influence line. The group total effect is the sum of the effects for a single group of static bridge loads, and can be used by the user to decide how to combine the different groups to maximise a particular effect.

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