Which scenario describes medium risk level in structural collapse?

The medium risk level in structural collapse situations encompasses scenarios where structural stability is compromised but does not immediately present a life-threatening hazard to rescuers or victims. Each of the scenarios illustrates a condition that could lead to further collapse but requires careful evaluation and management.

A partly collapsed concrete structure presents risks due to its incomplete stability; while it may not be entirely fallable, there is potential for further collapse depending on load distribution and conditions within or around the debris.

A racked wood building of three or more stories exemplifies medium risk since the structural framing may have altered significantly, leading to instability. The height and complexity of multi-story wood construction contribute to the potential for more serious collapse, especially under adverse conditions such as additional loading or environmental factors.

Free-standing unreinforced masonry walls that are out of plumb also fit the medium risk category, as the walls lack structural support and are prone to falling over, particularly in adverse weather conditions, vibrations, or when subjected to additional loads.

By recognizing that all these scenarios exhibit the characteristics of medium risk—instability yet not an immediate life-threatening collapse—option D correctly encompasses all conditions that fall into this classification. Such identification helps in formulating responses that prioritize safety while addressing the situation effectively.