The purpose of this article is to provide for the regulation of lawfully existing nonconforming lots, buildings, structures and uses. It is the intent of this chapter to allow such nonconformities to continue, unchanged, but not to encourage their continuance, until their eventual elimination, either upon the completion of normal useful life or through the process of amortization, in accordance with the authority granted by Section 5/11-13-1 of Chapter 65 of the Illinois Compiled Statutes, 1994.