Whenever a legal nonconforming structure or building has been damaged by fire, flood, wind, explosion, earthquake, war, riot, unlawful act, or Act of God, it may be reconstructed and used as before if it be reconstructed within twelve (12) months or three hundred and sixty-five (365) days after such calamity, unless the damage to said structure or building equals or exceeds fifty (50) percent of its assessed value. In such cases, the reconstruction shall be in complete conformance with the provisions of this chapter.