The lawful nonconforming structure existing at the time of the adoption or amendment of this Chapter may be continued although its size or location does not conform with the lot width, lot area, yard, height, parking and loading, and access provisions of this Chapter. However, it shall not be extended, enlarged, reconstructed, moved or structurally altered except when required to do so by law or order or so as to comply with the provisions of this Chapter. Present uses of buildings, signs, and premises may be continued even though they do not conform to the restrictions of this Chapter. However, structure repairs or alterations of such buildings or premises shall not exceed fifty percent (50%) of their assessed value at the time they become nonconforming unless a building or premises conforming to this Chapter results. Any nonconforming use that is abandoned for one (1) year shall be discontinued permanently.