Then you have to define members of truss by typing numbers of two joints corresponding to two ends of each member. For example, numbers 3 and 2 correspond to truss member with end joints 3 and 2 and with internal force N₂₃=N₃₂. The total number of truss members is equal to 2*n-3.

Also you have to define vertical V_j and horizontal H_i constraints (reactions) by entering corresponding joint numbers j and i where they are applied. It can be one horizontal plus two vertical constraints or one vertical plus two horizontal ones, but their total number must be equal to 3.

Then you have to enter external forces, which should be represented by their vertical Y_j and horizontal X_j components. Components are considered as positive if they act toward the positive directions of the corresponding coordinate axes. Here the subscript corresponds to the number of joint j where the force is applied.

To calculate the same truss structure under different load you do not need to enter structure properties again after first calculation. Just go back to the previous web page clicking on “back” button of your web browser. You will see the truss unloaded. Enter new values for load and click “calculate” button to calculate the truss under new load.

As a result you will obtain reactions and internal forces. The positive values correspond to tension forces, but negative values of internal forces correspond to compressed truss members. In addition all steps of the solution will be represented by formulas and considered truss under given load will be sketched. For calculation internal forces of the same truss under another load you can go back to the previous page of calculation.