Static equilibrium

In order to perform any calculations on forces in truss structures, the equations of equilibrium are used. These equations use the fact that the structure is in equilibrium if there is no resultant force or moment following from Newton's 1st law. For now we only look at the forces in the x and y direction, thus the equilibrium equations are as follows:

Where $F_x [N]$ is equal to forces in the $x$ direction, $F_y [N]$ to forces in the $y$ direction and $M_p [Nm]$ to the moment around a pivot point $p$.

When using these equations, the sign is very important so one should always be very careful and consistent with the sign.

The necessary equations for calculating forces in a truss structure are now explained, these can be used later on when actually performing the calculations. Before calculating these forces, it needs to be checked if the structure is statically determinate or not. Take a look at the next article for an explanation on how to check this.