Defining new load cases
Document history.
- 2023-03-30
- Added note that axle width is fixed for load case. Trains with differing axle widths cannot be represented as a single load case.
- 2023-03-22
- Corrected header in example file to show final two terms.
- Added default values for axle width and minimum width to carry terms in table.
- Altered note against axle width in table to state that "axle" width for rail wheel loads should be 0.8 (the initial distribution specified in 025) and wheel loads for road vehicles should be a suitable patch width. (Version before change said axle width for wheel loads should be 0.)
- First version.
Archie-M does not have a graphical load case editor, but the load case files are simple text files with the .ldf extension. You can write one from scratch, or (recommended) start with an existing load case that is similar to what you need and edit it.
The standard load files are in a subfolder of the Archie-M installation folder (where ArchieM.exe resides) called "Load". The table below gives examples of where the standard loads will be found depending on the location of the ArchieM.exe.
| Location of exe | Standard load files folder |
| C:\Program Files\Obvis\Archie-M\ArchieM.exe | C:\Program Files\Obvis\Archie-M\Load\ |
| \\server01\ArchieM\ArchieM.exe | \\server01\ArchieM\Load\ |
The .ldf files follow a simple line-based delimited text format. A line can be one of:
- Blank (empty, or only spaces or tabs)
- A comment (first non-blank character is a # symbol)
- A family header
- A group header
- A load case definition
Lines of types 1 and 2 are ignored. Lines of type 3 and 4 define the structure of the load cases. Otherwise a line defines a load case.
Let's look at the "AWR axles no impact.ldf" file distributed with Archie-M version 2.5.1. The full file is as follows. (The header has been corrected to show the full format and match the data in the file.)
# This file contains load case descriptions# The format of the file is as follows:### Name, GVW (informational), No. of Axles, Front Overhang, Axle load, <pos, Axle load,> Rear Overhang, Axle width; Minimum width to carry %FAMILY: AWR Axles from BD 21/01 %GROUP: Single axle Single Axle, 11.5, 1, 1, 11.5, 1, 1.8; 2.5 %GROUP: Double axle bogies Double Axle (>1.0 m), 16, 2, 1, 8.0, 1.02, 8.0, 1, 1.8; 2.5 Double Axle (1.3 m), 18, 2, 1, 9.0, 1.30, 9.0, 1, 1.8; 2.5 Double Axle (1.3 m air), 19, 2, 1, 9.5, 1.30, 9.5, 1, 1.8; 2.5 Driving Axle (1.3m air), 19, 2, 1, 11.5, 1.3, 7.5, 1, 1.8; 2.510.5t Drive Axle (1.3m), 19, 2, 1, 10.5, 1.3, 8.5, 1, 1.8; 2.5 ND Double Axle (1.8 m), 20, 2, 1, 10., 1.8, 10.0, 1, 1.8; 2.5 EU double axle ND (1.8 m), 20, 2, 1, 11, 1.5, 11, 1, 1.8; 2.5 %GROUP: Triple axle bogies Triple Axle (<2.6 m), 21.00, 3, 1, 7.00, 0.70, 7.00, 0.70, 7.00, 1, 1.8; 2.5 Triple Axle (>2.6 m), 24.00, 3, 1, 8.00, 1.32, 8.00, 1.32, 8.00, 1, 1.8; 2.5
If we open the "Apply live load" dialog in Archie-M 2.5.1, we see a list in the left hand pane.
The top item in a fresh installation is "AWR Axles from BD 21/01" - this is the family defined in the file above by the line:
%FAMILY: AWR Axles from BD 21/01
If we expand the "AWR Axles from BD 21/01" family by clicking on the small + to the left, we see a second level of headings.
These match the groups defined in the file above, for example:
%GROUP: Single axle
Expanding these group headings, we see that the next and final level is the load cases themselves.
A load file can include any number of load families, each load family can contain any number of load groups, and each load group can contain any number of load cases.
The format of the family and group definition lines is simple - they start with either %FAMILY: or %GROUP: and then give the text that will appear in the load case dialog.
Now lets look at the definition of the load cases themselves. The standard load files include a comment line near the top that gives the format for load case definitions:
# Name, Gross Weight, No. of Axles, Front Overhang, Axle load, <pos, Axle load,> Rear Overhang, Axle width; Minimum width to carry
(You may find that some of the standard load files, like the example above, don't list the last two items. This will be fixed in the next release. In the mean time, default values of 1.8m are used.)
The # symbol just marks this line as a comment. Don't include a # on load case definition lines, or they'll be treated as comments and ignored.
Each load case is defined by a series of fields separated by commas, and a final field marked by a semicolon. The fields are as follows.
| Field name | Field meaning | Content | Notes |
| Name | Text that appears in load case dialog | Text | |
| GVW | The gross weight of the vehicle in tonnes | Decimal | This field is currently ignored by Archie-M |
| No. of Axles | The number of axles in the load case | Integer | |
| Front Overhang | Limits how close distinct load cases can placed on the bridge (but not used at the moment) | Decimal | |
| Axle load | The first axle load in tonnes | Decimal | |
| pos | The offset to the next axle in m | Decimal | This field and the following are repeated as necessary |
| Axle load | The nth axle load in tonnes | Decimal | This field and the previous are repeated as necessary |
| Rear Overhang | Limits how close distinct load cases can placed on the bridge (but not used at the moment) | Decimal | |
| Axle width | The width of the axle in m. Defaults to 1.8m if this term and the next are omitted. | Decimal | Use 0.8 for a rail wheel load; a suitable patch width for road. All axle widths in a load train are identical (see article Load trains and short loads). |
| Minimum width to carry |
The minimum bridge width required to carry this vehicle. Defaults to 2.5m if this term is omitted. | Decimal | Archie-M will refuse to apply a load to a bridge that is not wide enough to carry it. |
Looking at the Single Axle load case:
Single Axle, 11.5, 1, 1, 11.5, 1, 1.8; 2.5
The title of the case is "Single Axle", the gross weight is 11.5 tonnes, there is 1 axle, the front overhang is 1m, the first axle load is 11.5 tonnes, the rear overhang is 1m, the axle width is 1.8m, and the vehicle cannot be applied to a bridge of less than 2.5m width.
Taking the last load case:
Triple Axle (>2.6 m), 24.00, 3, 1, 8.00, 1.32, 8.00, 1.32, 8.00, 1, 1.8; 2.5
The title of the case is "Triple Axle (>2.6 m)", the gross weight is 24 tonnes, there are 3 axles, the front overhang is 1m, the axle loads are 8 tonnes at 1.32m spacing, the rear overhang is 1m, the axle width is 1.8m, and the vehicle cannot be applied to a bridge of less than 2.5m.