If a building occupied by a non-conforming use is destroyed by fire, explosion, or other cause, it may not be reconstructed or rebuilt except to conform to the requirements of this article. However, nothing in this article shall be constructed to prevent restoration of a building destroyed or damaged to the extent of not more than sixty percent (60%) of its reasonable value by fire, explosion, acts of God, or other casualty, not the continued occupancy or use of such building or part thereof which existed at the time of such partial destruction.