Which scenario would likely lead to problems in structural members?

Heavy machinery operation poses a significant risk to structural members due to the excessive loads and dynamic forces it generates. When heavy machinery is in operation, it can introduce stresses that exceed the design limits of the structural elements, especially if the machinery is not properly accounted for in the original design. This can lead to bending, buckling, or even failure of beams, columns, and other supporting structures.

For example, if a building is not specifically designed to handle the weight and movement of heavy equipment, such as cranes or forklifts, the structural integrity could be compromised. Additionally, vibrations and impacts from heavy machinery can further weaken structural connections and materials over time, increasing the likelihood of failure.

While other options might seem plausible, they do not typically impose the same immediate and severe threats to structural integrity. Regularly scheduled maintenance helps ensure that any wear and tear or potential weaknesses are identified and addressed. Lack of people in a building typically does not affect structural members, as buildings are designed to stand empty. Dropping temperature conditions can have effects, such as contraction of materials, but this is usually managed through engineering design and does not create the same risk level as heavy machinery operation.