Why must all connected plies within the grip of a high-strength bolt be steel?

The reasoning behind the correct answer centers on the properties and behavior of high-strength bolts when installed in steel connections. High-strength bolts are designed to create clamping force between connected elements, and this requires consistent and predictable material responses.

When all connected plies within the grip of a high-strength bolt are made of steel, the tension applied to the bolt is effectively transferred through the steel components without any interference or deformation that would occur if softer or compressible materials were present. If a compressible material were included in the assembly, it would deform under the load, preventing the development of adequate bolt tension. This could lead to a failure of the connection over time as the bolt may loosen or fail to maintain the necessary clamping force for structural integrity.

Steel provides a uniform response to both the application of force and the resulting stress, ensuring that the high-strength bolt functions as intended to hold the connected elements firmly together. This consistency is crucial for the performance and longevity of structural connections in steel construction.