Optimal values of seismic design coefficients considering variations of indirect economic losses

Abstract

In order to attain optimum design values in the optimization process, it is necessary to have both initial cost functions and losses due to earthquakes. These costs are described in terms of design parameters, usually the seismic design coefficient or the vibration period. Among the losses caused by earthquakes, there are indirect economic losses called intangibles which may involve human lives. Here we compute a lower limit to the social value of an anonymous life, in the sense of how much society is willing to invest in order to preserve a human life. The human capital point of view is adopted, and it is assumed that the value of human life would be the expected present value of the income that a person would have earned in the event that he/she had lived. Then we resort to the classical reliability theory and use concepts such as probability of failure, reliability function, hazard function, and their relationships. In order to explore the influence of intangibles, optimum design coefficients are computed for a specific site considering that earthquake arrival times constitute a Poisson process. The results show that the influence of indirect economic losses in the computation of seismic design coefficients does make a difference and should not be ignored or assigned arbitrarily.