As a result of an earthquake, the City Administrator may determine through either an ATC 20 procedure or through subsequent discovery any structure or portion thereof to be in an unsafe condition as defined by State law.  As a result of making this determination, the City Administrator may declare the structure or portion thereof to be a public nuisance and to be repaired or rehabilitation as provided in Subsections 24.85.056 A.-C., or abated by demolition or removal in accordance with Portland City Code Title 29.  For the purposes of this Section, an “unsafe condition” includes, but is not limited to any portion, member or appurtenance of a building that has become detached or dislodged or appears likely to fail or collapse and injure persons or damage property; or any portion of a building or structure that has been damaged to the extent that the structural strength or stability of the building is substantially less than it was prior to the damaging event.

1. A.  Buildings built prior to January 1, 1974 with lateral support systems that have unsafe conditions must be repaired or improved to resist seismic forces such that the repaired lateral system conforms to the ASCE 41-BPOE improvement standard.
   1. 1.  Where less than 50 percent of the lateral support system has been damaged, only the damaged elements must be repaired.
   2. 2.  Where 50 percent or more of the lateral support system has been damaged, then the entire lateral support system must be repaired to resist seismic forces such that the repaired system conforms to the ASCE 41-BPOE improvement standard.
2. B.  Buildings built on or after January 1, 1974 with lateral support systems that have unsafe conditions must be repaired or improved to resist seismic forces such that the repaired lateral system conforms to the code to which the building was originally designed, but not less than that required to conform to the ASCE 41-BPOE improvement standard.
   1. 1.  Where less than 50 percent of the lateral support system has been damaged, only the damaged elements must be repaired.
   2. 2.  Where 50 percent or more of the lateral support system has been damaged, then the entire lateral support system must be repaired to resist seismic forces such that the repaired system conforms to the code to which the building was originally designed, but not less than that required to conform to the ASCE 41-BPOE improvement standard.
3. C.  New lateral system vertical elements must be compatible with any existing lateral system elements, including foundations. In multistory buildings, the engineer must confirm that the new lateral system vertical elements do not introduce soft or weak story seismic deficiencies, as defined by ASCE 41, where they did not previously exist, or make existing conditions more hazardous.