Any advertisement, advertising sign or advertising structure which is constructed, erected, operated, used, maintained, posted or displayed in violation of this article is hereby declared to be a public and private nuisance and shall be forthwith removed, obliterated or abated by the City or its representatives, and for that purpose they may enter upon private property without incurring any liability therefor; provided, that if any outdoor advertising structure or outdoor advertising sign of the value of one hundred dollars ($100.00) or more bears thereon the name of the owner thereof, and such owner holds an unexpired license issued under Section 1731.04, such owner shall be given written notice of the alleged violation and shall have thirty days after the receipt thereof within which to show that the advertisement, advertising sign or advertising structure does not violate this article.