If a nonconforming structure or a structure occupied by a nonconforming use is destroyed by fire, act of God or other cause, it may not be rebuilt except to the provisions of this ordinance. In the case of partial destruction of a nonconforming use not exceeding seventy-five (75%) percent of its reasonable value, reconstruction may be permitted after a hearing and favorable action by the City Council, but the size and function of the nonconforming use shall not expand.