What type of automobile structure is welded and/or bonded into one unit?

The term that describes an automobile structure that is welded and/or bonded into one unit is "unibody." This design approach integrates the vehicle's body and frame into a single cohesive structure, which offers several benefits, such as reduced weight, improved rigidity, and enhanced safety performance during collisions.

Unibody construction enables the vehicle to have crumple zones designed to absorb impact energy, distributing crash forces more effectively throughout the structure. This type of construction is prevalent in modern vehicles, especially passenger cars and many crossover SUVs, as it allows for more efficient use of materials and space compared to traditional body-on-frame designs.

In contrast, other types of automobile structures, such as body-on-frame, consist of a separate body mounted on a chassis frame, leading to greater weight and less structural rigidity. Modular and monocoque refer to different concepts, with monocoque indicating a construction style where the shell supports both structural and load-bearing functions, though it doesn’t specifically imply the welding or bonding as predominately as unibody does. Thus, unibody is the most accurate answer in this context.