PROPERTY LOADS TRUCK [lname] [lnumb] part file [LOADPATH]loadpath [[START] start-point] [[LANE] lane-number] [REVERSE]

 

OR PROPERTY LOADS TRUCK [lname] [lnumb] part file [START] start-point [END] end-point STEPS/RATIO increment [[LANE] lane-number] [REVERSE]

           

This command is used to define a moving load, it is currently only available within the DIANA environment. The load type name 'TRUCK' is used here for illustration purposes.

lname = name of the load, used for later references.

lnumb = loadcase number of the first stopping position (integer, default=1).

part = part that is affected by the moving load, (a line or a set of lines).

file = name of the file that contains the moving load data.

loadpath = locations where the moving load is to be applied, (a line or a set of lines).

start-point = point used to define the first moving load application point.

end-point = point used to define the last moving load application point.

STEPS = keyword to specify that increment is given as an absolute distance.

RATIO = keyword to specify that increment is given as a ratio.

increment = increment value: positive for STEPS, in range [0-1] for RATIO.

lane-number = lane number for the moving load (integer, default=1).

REVERSE = keyword to specify that the moving load direction is reversed.

A moving load is a group of point loads representing a vehicle that is moved along a defined path represented by a number of locations (called application points) where the group of loads is to be applied. A stopping position represents one of the moving load configurations where the group of point loads is applied to one of the application points. The moving load thus defines a range of loadcases where each loadcase corresponds to a stopping position.

The group of point loads which might typically represent a large vehicle is defined in a data file that may also contain picture data for the load. An example of such a data file is given in Appendix K of the FEMGV User Manual Appendices. FEMGEN expects the data file to be either in the current working directory or in the directory specified by the environment variable FG_PRE_LOD.

The path along which the load is to be moved is defined either by a chain of FEMGEN geometric lines so that the line divisions will give the load application points, or by a start point, an end point and an increment value to define the start, intermediate and end application points.

The structure which is affected by the moving load is defined with a FEMGEN set of geometric lines or as a single FEMGEN line. This/these line(s) must be part of meshed geometry. If there are several lines, they must form an unbroken chain.

There is considered to be a point load at each of the vehicle axles. The moving load stopping positions are defined such that the vehicle front axle is stopped at each of the load application points and the vehicle remaining axles are also stopped at the first and last application points. These stopping positions are ordered by FEMGEN so that the vehicle moves forwards. Each stopping position is internally allocated a loadcase number starting from number lnumb .

Notes:

1.

Moving load data filename
The name of the moving load datafile must not be more than 20 characters.

2.

Line(s) constituting the loadpath
The loadpath can be a single line, but not a combined line, or it can be a set of lines. The set of lines must be such that the lines form an unbroken chain. The lines do not have to be ordered in the set as this is done by FEMGEN internally. If the angle between 2 adjacent lines is greater than 5 degrees a warning is issued.

3.

Line divisions in the loadpath
When the moving load is defined by a loadpath, the numbers of line divisions control the number of load application points and may contain a grading value.

4.

Loadpath start point
If a start point is given it must be consistent with the loadpath: it should be one end of the line or chain of lines. If it is not specified then the start point will default to the end point of the first of the two extreme lines in the chain.

5.

STEPS increment
Where the path of the load is defined by a start-point and an end-point the STEPS option can be used to define the application points in absolute terms. The increment must be a positive number and represents the distance between the application points.

6.

RATIO increment
Where the path of the load is defined by a start-point and an end-point the RATIO option can be used to define the distance between application points as a proportion of the total loadpath length. The value given for RATIO must be between 0. and 1.

7.

REVERSE option
With the REVERSE option, the start and end points are implicitly swapped and the orientation of the vehicle is reversed so that it always moves forwards. See example 4.

8.

Display of moving loads
Moving loads can be displayed by selecting them with 'LABEL MESH LOADS lname' and a specific stopping position can be shown by using the command 'LABEL OPTIONS LOADS POSITION'. Alternatively, moving loads can be displayed at a specific stopping position by giving a loadcase number in the command 'LABEL MESH LOADS lnumb'. In this case all loads (moving loads and non-moving loads) that are part of the given loadcase number will be shown.

Examples:

1.

PROPERTY LOADS TRUCK LO1 11 SET1 H2S16T16 SET2

Define a moving load called LO1 that is applied to set SET1 using load data given by the file H2S16T16. The start point is the first point of the first (free end) line of set SET2 and the load travels along set SET2 stopping at each line division. The first stopping position is given loadcase number 11.

 

Figure 2.115: Moving load defined by loadpath

2.

PROPERTY LOADS TRUCK LO2 1 L1 TRUCK1 START P1 END P2 STEPS 1.5 2

Define a moving load called LO2 that is applied to line L1 using load data given by the file TRUCK1. The load travels from P1 to P2 and stops at points separated by a distance of 1.5 (i.e. P1, P1+1.5, P1+(2*1.5), ... , P2). The lane number is set to 2. The first stopping position is given loadcase number 1.

3.

PROPERTY LOADS TRUCK LO3 1 L1 TRUCK2.DAT P1 P2 RATIO 0.2

Define a moving load called LO3 that is applied to line L1 using load data given by the file TRUCK2.DAT. The load travels from P1 to P2 and stops at points every 0.2 of the distance between P1 and P2. The first stopping position is given loadcase number 1.

4.

PROPERTY LOADS TRUCK LO4 2 SET1 TRUCK2 P2 P4 RATIO 0.25 REVERSE

Define a moving load called LO4 that is applied to set SET1 using load data given by the file TRUCK2. With the option REVERSE selected, the load travels from P4 to P2 and stops at points every 0.25 of the distance between P2 and P4. The first stopping position is given loadcase number 2.

 

Figure 2.116: Moving load defined by start and stop points, an increment and REVERSE

See also the following commands

'LABEL GEOMETRY LOADS'
'LABEL MESH LOADS'
'LABEL OPTIONS LOADS POSITION'
'UTILITY DELETE LOADS'
'UTILITY TABULATE GEOMETRY LOADS'