ABSTRACT
ABSTRACT: The large randomness of earthquake ground motions is one of the main problems for aseismic design, as it makes uncertain the effectiveness of design decisions. In advanced earthquake-resistant design an alternative to incorporate ground motion uncertainty is to perform a reliability-based optimization, consisting in minimizing the cost subject to keeping the failure probability less than a certain threshold. The use of structural passive or active control necessarily implies a severe reduction of the allowable failure probabilities, thus making rather more expensive the application of reliability-based optimization. In addition, a major problem in applying LQR control is that it is subject to arbitrary selection of the relative weights of the story displacements and control forces. For these reasons it is convenient to apply a different strategy than the reliability-based design to overcome these difficulties and drawbacks. In this chapter, the concept of robust optimal design is used. It consists in minimizing the structural cost in such a way that the standard deviations of the responses are less than certain thresholds, thus yielding the optimal values of the weights with due regard to the uncertainties present in the system. The adequate computation of the response standard deviations in view of the large uncertainties of the ground motion parameters is also discussed and the application of a practical procedure is suggested and illustrated for a passive control case.
