Still on Frame4, Julien asked if provision could be made for application of local loads, i.e. loads perpendicular to sloping members, rather than just horizontal or vertical.  This will actually be incorporated in the spreadsheet “real soon now”, but it makes a good example of how the program can be made more versatile with the use of formulas on the spreadsheet, so that’s what I have done in this example.  The example is a simple twin portal frame structure, with perpendicular downward loads of 10 kN/m applied to the beams facing left, and perpendicular upward loads of 5 kN/m applied to those facing right.

Twin Portal Frame Structure

The formulas entered to calculate the equivalent global loads are shown below:

Calculation of global loads, click for full size view

For each roof member two load lines are required, to calculate the X and Y loads, from the input perpendicular loads, and the beam slope.  The calculated global load can then be transferred to the input area.  The resulting output results and deflected shape are shown below:

Output Results

Deflected shape

This technique can be extended to allow quite sophisticated analyses; for instance it would be possible to include geometric non-linearity by adjusting the node coordinates after each run, or material non-linearity by adjusting the section properties. The only word of warning is that the rows below the designated data entry areas must not be used for other purposes.