If a lattice boom touches or rests on a structure, how do the loading conditions change?

When a lattice boom touches or rests on a structure, the loading conditions change predominantly because the mechanics of how the forces interact with the boom alter significantly. In this case, the transition from compression to bending occurs due to the introduction of support from the structure.

When the boom is merely suspended without contact, it primarily experiences compressive forces along its length as it supports itself and any load it carries. However, when the boom comes in contact with a structure, the loading conditions shift because the point of contact can create moments that introduce bending stress in addition to the compressive forces.

This bending occurs because the weight carried by the boom may not be distributed evenly and could create a moment around the point of rest, leading to bending effects in the boom. Understanding these changes in loading conditions is crucial for safety and structural integrity, influencing how the boom is utilized in lifting operations and necessitating careful assessment of the loads applied to the boom and the support structure.