What are the Degrees of Freedom (DOFs) restrained for Truss joints?

In the context of truss analysis, the Degrees of Freedom (DOFs) at truss joints are crucial for understanding how the structure behaves under loads. Truss joints are primarily designed to facilitate the transfer of axial loads while allowing rotational freedom.

At the joints of a truss, the only movements constrained are translations. This means that the joints should not move in any of the three linear directions (along the x, y, and z axes). As a result, the joints are considered to have three translational degrees of freedom that are restrained.

However, truss joints are permitted to rotate freely. This is important as it allows the truss members to pivot as needed under load, thereby maintaining stability and ensuring that forces are appropriately distributed throughout the structure.

The reason why the correct answer is focused solely on three translational restraints is that this aligns with the fundamental design of trusses, which is intended to resist only axial loads while allowing for rotations at the joints. This concept is foundational in structural engineering and is why option detailing three translations as restrained is accurate in describing the constraints at truss joints.