What aspect can indicate redundancy in a structural frame when an extra reaction is added?

The correct answer highlights the significance of the member count in understanding structural redundancy. In structural engineering, redundancy refers to the inclusion of additional structural elements that do not contribute to the primary load-bearing function but provide backup in case of failure of one or more components. When an extra reaction is added to a frame, it implies that there’s an additional point of support that the structure can rely upon, which serves to distribute loads more effectively and maintain stability.

When analyzing a frame for redundancy, the overall number of members is crucial. If an extra reaction leads to an increase in the number of structural members, it often signals that the design intentionally incorporates redundancy. This should enhance the ability of the structure to redistribute loads if one member fails, ultimately leading to a more robust and resilient design.

While increased stability and joint load distribution are important considerations in the design process, they do not directly indicate redundancy in the way that a change in member count does. A newly added reaction might influence how loads are shared among existing members, but the key indicator of redundancy lies squarely with the structural elements themselves—their quantity and the relationships they create within the overall frame system. Structural inefficiency, although a factor in design choices, does not denote redundancy effectively in this context. Therefore