What is the term used to describe two stairwells situated in the same shaft with alternating standpipes on floors?

The term that describes two stairwells situated in the same shaft with alternating standpipes on floors is known as scissor stairs. This design allows for an efficient use of space and can enhance both accessibility and safety in a building. Scissor stairs improve egress during an emergency by providing two means of escape from a single floor, and having alternating standpipes ensures that each stairwell maintains adequate fire protection coverage. This configuration is useful in high-rise buildings where maximizing space while providing safety features is critical.

The other options may not accurately reflect this specific configuration. For example, double helix stairs typically refer to a spiral configuration rather than a dual set within the same shaft. Parallel stairs simply describe two staircases running alongside each other but do not necessarily involve the specific design features or safety measures attributed to scissor stairs. Interleaved stairs could refer to stairs that are not directly parallel or that intertwine but do not accurately capture the concept of alternating standpipes within a shaft.