Minimum Building Life-Cycle Cost Design Criteria. II: Applications

Abstract

The design criteria for a nine-story office building, subject to earthquakes and winds, are developed based on the method in the companion paper. The seismic and wind hazards, structural response analyses, and cost estimates are based on recent literature. Structural limit states in the nonlinear range and consequences are considered. The optimal design is obtained by minimizing the total expected life-cycle cost using a numerical procedure. A sensitivity analysis is conducted comparing the optimal design to the important but controversial parameters, such as design life, death and injury cost, structural capacity uncertainty, and discount rate. The method is applied to design under earthquakes, winds, and both hazards at Los Angeles, Seattle, and Charleston, South Carolina, and compared with current design. As expected, the seismic load controls the optimal design in Los Angeles. The optimal design is “dominated” by seismic load in Seattle and wind load in Charleston. These hazards, however, do not “control” or “govern” the design, for the lesser hazard still contributes significantly. Also, contrary to common belief, uniform reliability against different hazards is not required.