Strengthening Buildings to a Life Safety Criterion

Abstract

This paper presents an approach to seismically strengthen buildings to a life-safety criterion. Existing buildings do not comply with most provisions of modern model building codes and, as a result, are often considered seismically deficient. Buildings identified as seismic hazards are often not rehabilitated because the cost of the rehabilitation proves uneconomical, but the buildings usually continue in use because there are no funds to replace the structure. Building occupants continue to be exposed to hazardous conditions until building owners are forced to rehabilitate or demolish the structure by legally mandated seismic rehabilitate programs. Attainment of economical strengthening schemes requires that one identify essential goals and approach the seismic rehabilitation problem from the perspective of trying to achieve these goals. If prevention of building collapse and preservation of life-safety are the objectives of seismic rehabilitation, acceptance of higher levels of building damage may be an acceptable tradeoff for a reduction in the seismic rehabilitation cost. Explicit consideration of the building's available ductility, existing stiffness, and permissible lateral displacement permit the introduction of strengthening systems that address the fundamental weaknesses in the existing building. This limits the expenditure of funds to that required to achieve the required level of life safety without having to spend money to unreasonably reduce damage levels.