Minimum building life-cycle cost design criteria. I: Methodology

In view of the large damage suffered in recent earthquakes and hurricanes, building design criteria are developed to protect life and reduce damage an d loss to an acceptable level. The problem is minimizing the expected total life-cycle cost with respect to the design load and resistance. Load uncer tainty includes occurrence time, intensity, and duration. The costs of cons truction, maintenance, and failure consequences, including deaths and injur ies, as well as discounting cast over time, are considered. Optimal values are obtained of design variables and target reliability under single and mu ltiple time-varying loads. Also investigated is sensitivity of the optimal design to important loading and structural parameters. The optimal design i s found to depend primarily on the limit state consequences (costs), and to a lesser degree on the structural life. For multiple hazards, the optimal design is controlled by the hazard with large uncertainty and severe failur e consequences. In a companion paper applications are given of the method t o design multistory office buildings against earthquakes and winds.