Present uses of buildings, signs and premises may be continued even though they do not conform to the restrictions of this chapter. However, structural repairs or alterations of such buildings, signs or premises shall not during its life exceed 50% of their assessed value at the time they become nonconforming unless a building, sign or premises conforming to this chapter results. Any nonconforming use that is abandoned for one year shall be discontinued permanently. A nonconforming structure damaged or destroyed by violent wind, vandalism, fire, flood, ice, snow, mold or infestation after March 2, 2006, may be restored in accordance with the provisions of § 62.23(7)(hc), Wis. Stats.