δis a random value of small displacement.

h_c is the height distance between points A and B before any loads are applied.

u_c is the necessary deflection of point A for point B to touch the floor.

It is calculated by solving phase 1.

h_s is the height distance between points A and C before any loads are applied.

e is the difference between the free length and the solid length of the spring.

– means the displacement is unknown and the corresponding load is null.

0 means the displacement is blocked (see Fig. 9).