Limiting range for live load

I am modeling the span between 4 trusses, trying to get the DF for the trusses based on a truck moving load.

The model I have has three beams framing into 4 trusses as a continuous simply supported beam w/ 3-rollers. My problem is  limiting the range where my load can go:


TYPE 1 0 0 0 XINC 0.05 XRA 8.30 54.65

I thought that XRA would allow me to limit the load from going on the curb on both sides of the truss... but I'm having an issue with the program syntax. Is it because the XRA should be given in terms of nodes not distance along the member or am I missing on something else here?


Thanks :)


  • any follow up with replies?  I have the same problem/question. Thanks

  • Hi Ana,

    This command doesn't utilize an XRANGE value at all. The range used is only for the vertical direction (Y or Z, in the case SET Z UP models). There is a default value that is very small, so it is recommended to provide a range value to in the event your deck is not exactly parallel to the horizontal plane (XZ or YZ, depending on orientation). The YRANGE or ZRANGE for the LOAD GENERATION command only takes a single value, which is added to the initial reference load location (given as 0,0,0 in your example above). Here is a link to the Moving Load information, including examples, general steps for the user interface, and reference material for the input file commands.

    So you will want to provide the initial point of the vehicle reference load on your model and then the incremental value which the loads are moved in each direction (XINC, YINC, ZINC). The program will then progress the vehicle loads by the specified increments until the last load is off the structure. A load case is generated for each of these positions. So, in short, you can then position your vehicle in the lane (i.e., off the curb) with the initial reference load coordinates.


    Jason Coleman, PE

    Bentley Systems
    Senior Manager Technical Content