The structural design of a building is what gives the building integrity, strength, and the ability to hold together the beautiful facades and architectural components that help us to identify them as buildings. In the early stages of the construction of say, a home, lets imagine wood framing is the only thing constructed. In this case, the layman could identify that those frames would eventually become home but could likely say that it's just the “bare bones”. Speaking of bones, many biological creatures have their “structural design” composed of a bone structure which gives them too, integrity, strength, and the ability to hold other components of their bodies together.