Which of the following is NOT one of the rules for determining zero-force members in a truss?

The correct choice regarding the rules for determining zero-force members in a truss is one that highlights the scenarios that identify members that do not carry load under specific conditions.

Understanding the various rules is essential for effectively analyzing trusses. The first rule states that if two collinear members meet at a joint with no external load or support reaction applied at that joint, they can be considered zero-force members. This is because if there is no force applied, these two members cannot sustain any tension or compression; hence, they do not contribute to the structural behavior under those conditions.

In contrast, the rule regarding two non-collinear members indicates that when they meet at a joint without any external forces being applied, these members will also be zero-force members. The third rule points to a scenario where three members join at a point, but if two of them are collinear and no external loads are acting on the joint, the third member, which is non-collinear, will also be a zero-force member due to the inability of the collinear members to create a force that can act on the third.

Finally, the situation involving two non-collinear members and an applied load that is collinear with one of them is slightly different, as this condition does not