The next step is to make sure the parameter you have just added has a formula to make it equal the beam weight (W) this is simply done by clicking family types and adding the letter W in the formula column. In this example it means that Wtkg = W
The family can now be saved and loaded into your project. It is time to create your schedule. Add the usual parameters to your schedule such as type mark or type, you will also have to add the length and your newly created parameter, in this example that is Wtkg.
Now it is time for the mathematical part, you need to create a calculated value. Click the calculated value tab and you will see the window below. Set the discipline to common, set the type to number and add a formula. The beam weight (W) multiplied by the beam length, this is then divided by 1000 to convert the final value into tonnes.
Note - Be cautious when scheduling the tonnage for anything that is not a UB or a UC section. The out of the box families for Angles, SHS and RHS sections have incorrect properties for the beam weight (mass per m) so it would be wise to check the steel weight properties in the families with a steel stock book, and make the changes as required.